Clinical Review

IN THIS ARTICLE

• Diagnostic criteria
• Pharmacologic management
• Patient education

A more severe variant of peptic ulcer disease, Zollinger-Ellison syndrome (ZES) is a rare, chronic, and potentially life-threatening ulcerative disorder. Because the syndrome can be easily misdiagnosed based on clinical presentation alone, primary care clinicians need to be aware of its diagnostic features and know when referral to a gastroenterologist is necessary. Clinicians should suspect ZES in patients with peptic ulcer disease that is refractory to traditional medications.

Caused by a gastrin-secreting neuroendocrine tumor of the pancreas or duodenum called a gastrinoma, ZES can be benign or malignant. It typically manifests in white men ages 30 to 50.¹ Due to the significant number of patients treated for a benign cause of peptic ulcer disease (eg, Helicobacter pylori or NSAID-induced ulcers) who are never tested for ZES, the exact incidence is difficult to determine.² However, it is estimated that approximately 0.1 to 3 people per million develop the disease annually.³

PATHOPHYSIOLOGY

Approximately 80% of gastrinomas occur in the “gastrinoma triangle,” outlined by the hepatic portal vein, neck and body of the pancreas, and latter two-thirds of the duodenum (see Figure).^1,4,5 Most gastrinomas involved in ZES occur sporadically, but there is a hereditary component associated with multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder.⁴

The overproduction and secretion of gastrin by the gastrinoma stimulates hypersecretion of hydrochloric acid.⁴ This is distinguished from high gastrin levels in the setting of fasting hypochlorhydria or achlorhydria, which may be caused by chronic atrophic gastritis, proton pump inhibitor (PPI) use, or pernicious anemia.⁵ The chronic hypersecretion of acid causes ulcerations to form. Most commonly, a single ulcer forms in the first portion of the duodenum.³

CLINICAL PRESENTATION

Patients with ZES often report vague abdominal pain that may mimic peptic ulcer disease on initial presentation. The widespread use of PPIs can mask symptoms, and one-fourth of patients present with no abdominal pain at all.⁶ Patients may also present with symptoms of GERD (ie, heartburn, chest pain, dysphagia).^1,4 Excessive acid production can lead to the development of Barrett esophagus, which can further complicate the management of ZES.⁶ Half of all patients with ZES have diarrhea, which can manifest on its own or be accompanied by other abdominal complaints, and is often attributed to lower GI problems such as Crohn disease.^1,7 Family history of MEN1 should raise suspicion for ZES; however, 80% of ZES cases occur sporadically.³

The physical exam may be within normal limits, and no physical finding is considered pathognomonic for ZES. Findings may include epigastric tenderness; pallor, due to an ulcer-related anemia or GI bleed; jaundice, if there is liver involvement; and esophageal or dental erosions, due to excessive acid.⁸

DIAGNOSIS

Patients with symptoms refractory to medical management should be referred to a specialist for further testing. Once a patient is referred, a gastroenterologist will perform lab tests and imaging studies. In order to be diagnosed with ZES, the patient must exhibit an acidic environment with a pH less than 2 and an inappropriate release of gastrin with a basal acid output greater than 15 mEq/h (or > 5 mEq/h in a patient with prior acid reduction surgery).^5,6

Fasting serum gastrin (FSG) is the initial study of choice, followed by a secretin-stimulating test when necessary.⁹ Diagnosis is established by an FSG level greater than 100 pg/mL; if more than 10-fold the normal level, no further testing is needed. However, results often range from 100 to 1,000 pg/mL.^6,10 At these values, further testing with secretin stimulation is warranted.⁹ The test is performed with an IV injection of secretin, and blood samples are obtained to measure serum gastrin levels.¹⁰ An increase greater than 100 pg/mL is considered positive; one greater than 200 pg/mL is diagnostic.³

Once lab tests have been performed, a series of imaging studies are indicated. Endoscopy is used to identify active ulcers and erosions due to long-term acid secretion.³ CT, MRI, and somatostatin receptor scintigraphy (a specialized form of imaging that is the study of choice for localizing gastrinomas) are performed to localize primary tumors and identify any metastatic disease that may be present.¹⁰ Finally, after lab tests and imaging studies have been completed, genetic screening for MEN1 is used to determine if the patient has a sporadic or hereditary gastrinoma.³

MANAGEMENT

Once ZES has been diagnosed, the specialist will refer the patient for surgical opinion. The main objectives of surgery are to determine whether the tumor is malignant via biopsy, and to resect the tumor to suppress the acid hypersecretion, if indicated in the absence of liver metastasis and large pancreatic tumor size. Medical management should begin immediately to prevent any further damage from prolonged gastric hypersecretion.¹

Pharmacologic options include PPIs, H2-receptor antagonists, and somatostatin analogues; PPIs are considered firstline therapy. Many patients with ZES require a higher dosage than is needed with typical GERD (60-100 mg/d vs 20-40 mg/d). Somatostatin analogues can be used in conjunction with PPIs and have been shown to inhibit tumor growth in patients with malignant ZES.¹

Once a ZES diagnosis has been made, the tumor(s) resected (if appropriate), and vagotomy considered or performed, patients will need routine follow-up with their gastroenterologist and their primary care provider, who can manage medications and recommend any lifestyle changes.⁵

PROGNOSIS

The most important prognostic factor of patients with ZES is whether the gastrinoma is benign or malignant. There are two patterns: aggressive disease (25%) and nonaggressive disease (75%).⁵ At diagnosis, 40% to 70% of patients with sporadic ZES present with lymph node metastases, and 20% to 40% present with liver metastases. Patients with liver metastases have a 10-year survival rate of 30%, compared to a 15-year survival rate of 83% in patients without liver metastases.^11,12

Along with the tumor itself, another prognostic factor to consider is the FSG level at diagnosis. Patients with higher FSG levels have decreased five- and 10-year survival rates compared to patients with lower FSG values. The 10-year survival rate for patients with a lower FSG value (0-499 pg/mL) is 86%, while the 10-year survival rate for those with a greater FSG value (> 1,000 pg/mL) is 73%.^11,12 Overall, the prognosis is good for patients with ZES. The 10-year survival rate is high, and management is possible with medications and surgical resection of the gastrinoma.

PATIENT EDUCATION

Once patients are diagnosed, treatment with PPIs is typically lifelong unless they are considered cured by surgical resection. Patients need to understand that compliance is necessary to properly manage symptoms; certain foods, alcohol, and tobacco can affect the condition, and lifestyle modifications should be made, as they would with typical GERD or peptic ulcer disease.

CONCLUSION

ZES is frequently overlooked, and patients often continue to experience unresolved symptoms related to hypergastrinemia. Due to its complexity and ability to mimic other disorders—as well as the implications of duodenal versus pancreatic location, and other disorders of the kidney or endocrine system suggestive of MEN1—ZES should be ruled out in any patient with unexplained persistent GERD, peptic ulcer disease, elevated FSG, chronic diarrhea, and/or abdominal pain.⁵

The gastrinoma itself is a well-differentiated and slow-growing tumor in the majority of cases, making the prognosis for ZES favorable for long-term survival. Proper pharmacologic management is instrumental for controlling symptoms and decreasing acid production. Surgical resection offers patients the best chance for a complete cure. Clinicians and patients should be well educated about ZES in order to successfully manage the disorder.

IN THIS ARTICLE

• Diagnostic criteria
• Pharmacologic management
• Patient education

A more severe variant of peptic ulcer disease, Zollinger-Ellison syndrome (ZES) is a rare, chronic, and potentially life-threatening ulcerative disorder. Because the syndrome can be easily misdiagnosed based on clinical presentation alone, primary care clinicians need to be aware of its diagnostic features and know when referral to a gastroenterologist is necessary. Clinicians should suspect ZES in patients with peptic ulcer disease that is refractory to traditional medications.

Caused by a gastrin-secreting neuroendocrine tumor of the pancreas or duodenum called a gastrinoma, ZES can be benign or malignant. It typically manifests in white men ages 30 to 50.¹ Due to the significant number of patients treated for a benign cause of peptic ulcer disease (eg, Helicobacter pylori or NSAID-induced ulcers) who are never tested for ZES, the exact incidence is difficult to determine.² However, it is estimated that approximately 0.1 to 3 people per million develop the disease annually.³

PATHOPHYSIOLOGY

Approximately 80% of gastrinomas occur in the “gastrinoma triangle,” outlined by the hepatic portal vein, neck and body of the pancreas, and latter two-thirds of the duodenum (see Figure).^1,4,5 Most gastrinomas involved in ZES occur sporadically, but there is a hereditary component associated with multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder.⁴

The overproduction and secretion of gastrin by the gastrinoma stimulates hypersecretion of hydrochloric acid.⁴ This is distinguished from high gastrin levels in the setting of fasting hypochlorhydria or achlorhydria, which may be caused by chronic atrophic gastritis, proton pump inhibitor (PPI) use, or pernicious anemia.⁵ The chronic hypersecretion of acid causes ulcerations to form. Most commonly, a single ulcer forms in the first portion of the duodenum.³

CLINICAL PRESENTATION

Patients with ZES often report vague abdominal pain that may mimic peptic ulcer disease on initial presentation. The widespread use of PPIs can mask symptoms, and one-fourth of patients present with no abdominal pain at all.⁶ Patients may also present with symptoms of GERD (ie, heartburn, chest pain, dysphagia).^1,4 Excessive acid production can lead to the development of Barrett esophagus, which can further complicate the management of ZES.⁶ Half of all patients with ZES have diarrhea, which can manifest on its own or be accompanied by other abdominal complaints, and is often attributed to lower GI problems such as Crohn disease.^1,7 Family history of MEN1 should raise suspicion for ZES; however, 80% of ZES cases occur sporadically.³

The physical exam may be within normal limits, and no physical finding is considered pathognomonic for ZES. Findings may include epigastric tenderness; pallor, due to an ulcer-related anemia or GI bleed; jaundice, if there is liver involvement; and esophageal or dental erosions, due to excessive acid.⁸

DIAGNOSIS

Patients with symptoms refractory to medical management should be referred to a specialist for further testing. Once a patient is referred, a gastroenterologist will perform lab tests and imaging studies. In order to be diagnosed with ZES, the patient must exhibit an acidic environment with a pH less than 2 and an inappropriate release of gastrin with a basal acid output greater than 15 mEq/h (or > 5 mEq/h in a patient with prior acid reduction surgery).^5,6

Fasting serum gastrin (FSG) is the initial study of choice, followed by a secretin-stimulating test when necessary.⁹ Diagnosis is established by an FSG level greater than 100 pg/mL; if more than 10-fold the normal level, no further testing is needed. However, results often range from 100 to 1,000 pg/mL.^6,10 At these values, further testing with secretin stimulation is warranted.⁹ The test is performed with an IV injection of secretin, and blood samples are obtained to measure serum gastrin levels.¹⁰ An increase greater than 100 pg/mL is considered positive; one greater than 200 pg/mL is diagnostic.³

Once lab tests have been performed, a series of imaging studies are indicated. Endoscopy is used to identify active ulcers and erosions due to long-term acid secretion.³ CT, MRI, and somatostatin receptor scintigraphy (a specialized form of imaging that is the study of choice for localizing gastrinomas) are performed to localize primary tumors and identify any metastatic disease that may be present.¹⁰ Finally, after lab tests and imaging studies have been completed, genetic screening for MEN1 is used to determine if the patient has a sporadic or hereditary gastrinoma.³

MANAGEMENT

Once ZES has been diagnosed, the specialist will refer the patient for surgical opinion. The main objectives of surgery are to determine whether the tumor is malignant via biopsy, and to resect the tumor to suppress the acid hypersecretion, if indicated in the absence of liver metastasis and large pancreatic tumor size. Medical management should begin immediately to prevent any further damage from prolonged gastric hypersecretion.¹

Pharmacologic options include PPIs, H2-receptor antagonists, and somatostatin analogues; PPIs are considered firstline therapy. Many patients with ZES require a higher dosage than is needed with typical GERD (60-100 mg/d vs 20-40 mg/d). Somatostatin analogues can be used in conjunction with PPIs and have been shown to inhibit tumor growth in patients with malignant ZES.¹

Once a ZES diagnosis has been made, the tumor(s) resected (if appropriate), and vagotomy considered or performed, patients will need routine follow-up with their gastroenterologist and their primary care provider, who can manage medications and recommend any lifestyle changes.⁵

PROGNOSIS

The most important prognostic factor of patients with ZES is whether the gastrinoma is benign or malignant. There are two patterns: aggressive disease (25%) and nonaggressive disease (75%).⁵ At diagnosis, 40% to 70% of patients with sporadic ZES present with lymph node metastases, and 20% to 40% present with liver metastases. Patients with liver metastases have a 10-year survival rate of 30%, compared to a 15-year survival rate of 83% in patients without liver metastases.^11,12

Along with the tumor itself, another prognostic factor to consider is the FSG level at diagnosis. Patients with higher FSG levels have decreased five- and 10-year survival rates compared to patients with lower FSG values. The 10-year survival rate for patients with a lower FSG value (0-499 pg/mL) is 86%, while the 10-year survival rate for those with a greater FSG value (> 1,000 pg/mL) is 73%.^11,12 Overall, the prognosis is good for patients with ZES. The 10-year survival rate is high, and management is possible with medications and surgical resection of the gastrinoma.

PATIENT EDUCATION

Once patients are diagnosed, treatment with PPIs is typically lifelong unless they are considered cured by surgical resection. Patients need to understand that compliance is necessary to properly manage symptoms; certain foods, alcohol, and tobacco can affect the condition, and lifestyle modifications should be made, as they would with typical GERD or peptic ulcer disease.

CONCLUSION

ZES is frequently overlooked, and patients often continue to experience unresolved symptoms related to hypergastrinemia. Due to its complexity and ability to mimic other disorders—as well as the implications of duodenal versus pancreatic location, and other disorders of the kidney or endocrine system suggestive of MEN1—ZES should be ruled out in any patient with unexplained persistent GERD, peptic ulcer disease, elevated FSG, chronic diarrhea, and/or abdominal pain.⁵

The gastrinoma itself is a well-differentiated and slow-growing tumor in the majority of cases, making the prognosis for ZES favorable for long-term survival. Proper pharmacologic management is instrumental for controlling symptoms and decreasing acid production. Surgical resection offers patients the best chance for a complete cure. Clinicians and patients should be well educated about ZES in order to successfully manage the disorder.

IN THIS ARTICLE

• Diagnostic criteria
• Pharmacologic management
• Patient education

A more severe variant of peptic ulcer disease, Zollinger-Ellison syndrome (ZES) is a rare, chronic, and potentially life-threatening ulcerative disorder. Because the syndrome can be easily misdiagnosed based on clinical presentation alone, primary care clinicians need to be aware of its diagnostic features and know when referral to a gastroenterologist is necessary. Clinicians should suspect ZES in patients with peptic ulcer disease that is refractory to traditional medications.

Caused by a gastrin-secreting neuroendocrine tumor of the pancreas or duodenum called a gastrinoma, ZES can be benign or malignant. It typically manifests in white men ages 30 to 50.¹ Due to the significant number of patients treated for a benign cause of peptic ulcer disease (eg, Helicobacter pylori or NSAID-induced ulcers) who are never tested for ZES, the exact incidence is difficult to determine.² However, it is estimated that approximately 0.1 to 3 people per million develop the disease annually.³

PATHOPHYSIOLOGY

Approximately 80% of gastrinomas occur in the “gastrinoma triangle,” outlined by the hepatic portal vein, neck and body of the pancreas, and latter two-thirds of the duodenum (see Figure).^1,4,5 Most gastrinomas involved in ZES occur sporadically, but there is a hereditary component associated with multiple endocrine neoplasia type 1 (MEN1), an autosomal dominant disorder.⁴

The overproduction and secretion of gastrin by the gastrinoma stimulates hypersecretion of hydrochloric acid.⁴ This is distinguished from high gastrin levels in the setting of fasting hypochlorhydria or achlorhydria, which may be caused by chronic atrophic gastritis, proton pump inhibitor (PPI) use, or pernicious anemia.⁵ The chronic hypersecretion of acid causes ulcerations to form. Most commonly, a single ulcer forms in the first portion of the duodenum.³

CLINICAL PRESENTATION

Patients with ZES often report vague abdominal pain that may mimic peptic ulcer disease on initial presentation. The widespread use of PPIs can mask symptoms, and one-fourth of patients present with no abdominal pain at all.⁶ Patients may also present with symptoms of GERD (ie, heartburn, chest pain, dysphagia).^1,4 Excessive acid production can lead to the development of Barrett esophagus, which can further complicate the management of ZES.⁶ Half of all patients with ZES have diarrhea, which can manifest on its own or be accompanied by other abdominal complaints, and is often attributed to lower GI problems such as Crohn disease.^1,7 Family history of MEN1 should raise suspicion for ZES; however, 80% of ZES cases occur sporadically.³

The physical exam may be within normal limits, and no physical finding is considered pathognomonic for ZES. Findings may include epigastric tenderness; pallor, due to an ulcer-related anemia or GI bleed; jaundice, if there is liver involvement; and esophageal or dental erosions, due to excessive acid.⁸

DIAGNOSIS

Patients with symptoms refractory to medical management should be referred to a specialist for further testing. Once a patient is referred, a gastroenterologist will perform lab tests and imaging studies. In order to be diagnosed with ZES, the patient must exhibit an acidic environment with a pH less than 2 and an inappropriate release of gastrin with a basal acid output greater than 15 mEq/h (or > 5 mEq/h in a patient with prior acid reduction surgery).^5,6

Fasting serum gastrin (FSG) is the initial study of choice, followed by a secretin-stimulating test when necessary.⁹ Diagnosis is established by an FSG level greater than 100 pg/mL; if more than 10-fold the normal level, no further testing is needed. However, results often range from 100 to 1,000 pg/mL.^6,10 At these values, further testing with secretin stimulation is warranted.⁹ The test is performed with an IV injection of secretin, and blood samples are obtained to measure serum gastrin levels.¹⁰ An increase greater than 100 pg/mL is considered positive; one greater than 200 pg/mL is diagnostic.³

Once lab tests have been performed, a series of imaging studies are indicated. Endoscopy is used to identify active ulcers and erosions due to long-term acid secretion.³ CT, MRI, and somatostatin receptor scintigraphy (a specialized form of imaging that is the study of choice for localizing gastrinomas) are performed to localize primary tumors and identify any metastatic disease that may be present.¹⁰ Finally, after lab tests and imaging studies have been completed, genetic screening for MEN1 is used to determine if the patient has a sporadic or hereditary gastrinoma.³

MANAGEMENT

Once ZES has been diagnosed, the specialist will refer the patient for surgical opinion. The main objectives of surgery are to determine whether the tumor is malignant via biopsy, and to resect the tumor to suppress the acid hypersecretion, if indicated in the absence of liver metastasis and large pancreatic tumor size. Medical management should begin immediately to prevent any further damage from prolonged gastric hypersecretion.¹

Pharmacologic options include PPIs, H2-receptor antagonists, and somatostatin analogues; PPIs are considered firstline therapy. Many patients with ZES require a higher dosage than is needed with typical GERD (60-100 mg/d vs 20-40 mg/d). Somatostatin analogues can be used in conjunction with PPIs and have been shown to inhibit tumor growth in patients with malignant ZES.¹

Once a ZES diagnosis has been made, the tumor(s) resected (if appropriate), and vagotomy considered or performed, patients will need routine follow-up with their gastroenterologist and their primary care provider, who can manage medications and recommend any lifestyle changes.⁵

PROGNOSIS

The most important prognostic factor of patients with ZES is whether the gastrinoma is benign or malignant. There are two patterns: aggressive disease (25%) and nonaggressive disease (75%).⁵ At diagnosis, 40% to 70% of patients with sporadic ZES present with lymph node metastases, and 20% to 40% present with liver metastases. Patients with liver metastases have a 10-year survival rate of 30%, compared to a 15-year survival rate of 83% in patients without liver metastases.^11,12

Along with the tumor itself, another prognostic factor to consider is the FSG level at diagnosis. Patients with higher FSG levels have decreased five- and 10-year survival rates compared to patients with lower FSG values. The 10-year survival rate for patients with a lower FSG value (0-499 pg/mL) is 86%, while the 10-year survival rate for those with a greater FSG value (> 1,000 pg/mL) is 73%.^11,12 Overall, the prognosis is good for patients with ZES. The 10-year survival rate is high, and management is possible with medications and surgical resection of the gastrinoma.

PATIENT EDUCATION

Once patients are diagnosed, treatment with PPIs is typically lifelong unless they are considered cured by surgical resection. Patients need to understand that compliance is necessary to properly manage symptoms; certain foods, alcohol, and tobacco can affect the condition, and lifestyle modifications should be made, as they would with typical GERD or peptic ulcer disease.

CONCLUSION

ZES is frequently overlooked, and patients often continue to experience unresolved symptoms related to hypergastrinemia. Due to its complexity and ability to mimic other disorders—as well as the implications of duodenal versus pancreatic location, and other disorders of the kidney or endocrine system suggestive of MEN1—ZES should be ruled out in any patient with unexplained persistent GERD, peptic ulcer disease, elevated FSG, chronic diarrhea, and/or abdominal pain.⁵

The gastrinoma itself is a well-differentiated and slow-growing tumor in the majority of cases, making the prognosis for ZES favorable for long-term survival. Proper pharmacologic management is instrumental for controlling symptoms and decreasing acid production. Surgical resection offers patients the best chance for a complete cure. Clinicians and patients should be well educated about ZES in order to successfully manage the disorder.

In this Update we review the results of 4 recent investigations that have important implications:

• the first analysis of the US Zika Virus Infection in Pregnancy Registry
• a study revealing an improved antibiotic regimen to prevent postcesarean infection
• an important new methodology for reducing the rate of perinatal transmission of hepatitis B virus (HBV) infection
• the risks and benefits of combination antiretroviral therapy (ART) in pregnancy.

Zika virus-associated birth defect rates similar regardless of symptom presence; first-trimester exposure has highest rate of anomalies

Honein MA, Dawson AL, Petersen EE, et al; US Zika Pregnancy Registry Collaboration. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA. 2017;317(1):59-68.

Honein and colleagues provide a summary of the data from the US Zika Virus in Pregnancy Registry (a collaboration between the Centers for Disease Control and Prevention and state and local health departments), estimating the proportion of fetuses and infants with birth defects based on maternal symptoms of Zika virus infection and  trimester of possible infection.

Related article:
Zika virus: Counseling considerations for this emerging perinatal threat

Details of the study

The authors evaluated the outcomes of 442 women who had laboratory evidence of a possible Zika virus infection during pregnancy. Overall, 26 infants (6%; 95% confidence interval (CI), 4%-8%) had evidence of birth defects related to the Zika virus. Of note, abnormalities were detected in 16 of the 271 children (6%; 95% CI, 4%-9%) born to women who were asymptomatic and 10 of 167 (6%; 95% CI, 3%-11%) children delivered to women with symptomatic infections. 

The most common birth defect was microcephaly, although other serious central nervous system abnormalities were noted as well. Nine of 85 women (11%; 95% CI, 6%-19%) who had exposure only during the first trimester had infants with birth defects. There were no documented abnormalities in infants born to mothers who developed Zika virus infection only in the second or third trimester. 

Related article:
Zika virus update: A rapidly moving target

Key study findings

This article is important for several reasons. First, the authors describe the largest series of pregnant women in the United States with Zika virus infection. All of these patients developed Zika virus infection as a result of foreign travel or exposure to sexual partners who had traveled to Zika virus endemic areas. Second, the authors confirmed findings that previously had been based only on mathematical models rather than on actual case series. Specifically, they demonstrated that the risk of a serious birth defect following first-trimester exposure to Zika virus infection was approximately 11%, with a 95% CI that extended from 6% to 19%. Finally, Honein and colleagues highlighted the key fact that the risk of a serious birth defect was comparable in mothers who had either an asymptomatic or a symptomatic infection, a finding that seems somewhat counterintuitive.

Read about prophylaxis for postcesarean infection

Two antibiotics before cesarean delivery reduce infection rates further than one agent

Tita AT, Szychowski JM, Boggess K, et al; for the C/SOAP Trial Consortium. Adjunctive azithromycin prophylaxis for cesarean delivery. N Engl J Med. 2016;375(13):1231-1241.

Tita and colleagues reported the results of a multicenter trial that was designed to assess whether a combination of 2 antibiotics, including one that specifically targets ureaplasma species, provided more effective prophylaxis against postcesarean infection than single-agent prophylaxis.

Details of the study

The Cesarean Section Optimal Antibiotic Prophylaxis (C/SOAP) trial was conducted at 14 centers in the United States and included 2,013 women who were at least at 24 weeks' gestation and who had a cesarean delivery during labor or after membrane rupture.

The authors randomly assigned 1,019 women to receive 500 mg of intravenous azithromycin plus conventional single-agent prophylaxis (usually cefazolin) and 994 women to receive a placebo plus conventional prophylaxis. The primary outcome was the composite of endometritis, wound infection, or other infection occurring within 6 weeks.

The authors observed that the primary outcome occurred in 62 women (6.1%) who received azithromycin plus conventional prophylaxis and in 119 women (12%) who received only single-agent prophylaxis. The relative risk of developing a postoperative infection was 0.51 in women who received the combined therapy. There were significant differences between the 2 groups in both the rates of endometritis (3.8% vs 6.1%, P = .02) and wound infection (2.4% vs 6.6%, P<.001). There were no differences between the groups in the frequency of the secondary neonatal composite outcome, which included neonatal death and serious neonatal complications.

Related article:
Preventing infection after cesarean delivery: 5 more evidence-based measures to consider

Efficacy of dual-agent prophylaxis

At present, the standard of care is to administer prophylactic antibiotics to all women having cesarean delivery, including women having a scheduled cesarean in the absence of labor or ruptured membranes. Multiple studies have shown clearly that prophylaxis reduces the frequency of endometritis and, in high-risk patient populations, wound infection, and that prophylaxis is most beneficial when administered prior to the time the surgical incision is made. The most commonly used drug for prophylaxis is cefazolin, a first-generation cephalosporin. The usual recommended dose is 2 g, administered immediately prior to surgery.^3,4

Although most centers in the United States traditionally have used just a single antibiotic for prophylaxis, selected recent reports indicate that expanding the spectrum of activity of prophylactic antibiotics can result in additional beneficial effects. Specifically, Tita and colleagues evaluated an indigent patient population with an inherently high rate of postoperative infection.⁵ They showed that adding azithromycin 500 mg to cefazolin significantly reduced the rate of postcesarean endometritis. In a follow-up report from the same institution, Tita and colleagues demonstrated that adding azithromycin also significantly reduced the frequency of wound infection.⁶ Of note, in both these investigations, the antibiotics were administered after cord clamping. In a subsequent report, Ward and Duff showed that the combination of azithromycin plus cefazolin administered preoperatively resulted in a combined rate of endometritis and wound infection that was less than 3%.⁷

Related article:
Preventing infection after cesarean delivery: Evidence-based guidance

C/SOAP trial confirmed lower infection rates with combined regimen

Results of the present study confirm the findings of these 3 investigations. The trial included a large sample size. The study was carefully designed, and the end points were clearly defined. It included only patients at increased risk for postoperative infection by virtue of being in labor or having ruptured membranes at the time of cesarean delivery. Patients who received standard prophylaxis, usually cefazolin, plus azithromycin had a significantly lower risk of postcesarean endometritis and wound infection compared with patients who received a single antibiotic. The overall risk of infection was reduced by an impressive 50%.  
 

Read about reducing HBV transmission

Tenofovir treatment in pregnant women with HBV reduces vertical transmission

Pan CQ, Duan Z, Dai E, et al; China Study Group for the Mother-to-Child Transmission of Hepatitis B. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016;374(24):2324-2334.

A multicenter, open-label, randomized, parallel-group investigation was conducted from March 2012 to June 2013 at academic tertiary care centers in 5 geographic regions of China. Two hundred mothers, who were positive for both hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) and who had HBV DNA concentrations of 200,000 IU/mL or greater, were randomly assigned in a 1:1 ratio to either tenofovir or to usual treatment. Exclusion criteria were coexistent viral infections or medical conditions, renal failure, laboratory abnormalities, fetal deformities, and use of many medications.

Related article:
5 ways to reduce infection risk during pregnancy

Details of the study

Women in the active treatment group received tenofovir 300 mg by mouth daily from 30 to 32 weeks' gestation until postpartum week 4. Patients were monitored every 4 weeks in the antepartum period for adverse events and laboratory abnormalities. In the postpartum period, mother-infant dyads were evaluated at weeks 4, 12, 24, and 28.

Primary outcomes were the rates of mother-to-child transmission and birth defects with, or without, tenofovir exposure. Secondary outcomes were the percentage of mothers who had an HBV DNA serum concentration of less than 200,000 IU/mL at delivery and the percentage of mothers with HBeAg or HBsAg loss or seroconversion at postpartum week 28. Safety outcomes included the adverse event profile of tenofovir in mothers and safety events in the mother-infant dyads. These outcomes encompassed  all adverse events and drug discontinuations in patients who received at least one dose of tenofovir.

Sixty-eight percent of mothers in the tenofovir group, compared with 2% of mothers in the control group, had HBV levels less than 200,000 IU/mL at delivery (P<.001). The rate of mother-to-child HBV transmission at postpartum week 28 was lower in the tenofovir group. In the intention-to-treat analysis, the rate was 5% (95% CI, 1-10; 5 of 97 infants) in the tenofovir group versus 18% (95% CI, 10-26; 18 of 100 infants) in the control group (P = .007). In the per-protocol analysis, the rate was 0% (95% CI, 0-3; 0 of 92 infants) in the tenofovir group versus 7% (95% CI, 2-12; 6 of 88 infants) in the control group (P = .01). Maternal and infant safety profiles were similar between the 2 groups, with the exception of elevated creatinine kinase and alanine aminotransferase levels in mothers treated with tenofovir. Maternal HBV serologic titers did not differ significantly between the 2 groups.

Study strengths and limitations

This study's strengths include a multicenter, randomized controlled design, with strict inclusion and exclusion criteria. The results are clinically relevant and of global impact, with potential to decrease morbidity and  mortality from HBV infection in children born to infected mothers. 

A limitation, however, is that the study was probably underpowered to detect small differences in the rate of birth defects between the tenofovir and usual-care treatment groups. Additionally, some patients ceased taking tenofovir in the postpartum time period. Abrupt cessation may be associated with acute, severe HBV exacerbation.  

Benefits of ART for reducing mother-to-baby HIV transmission outweigh higher risk of adverse outcomes

Fowler MG, Qin M, Fiscus SA, et al; IMPAACT 1077BF/1077FF PROMISE Study Team. Benefits and risks of antiretroviral therapy for perinatal HIV prevention. N Engl J Med. 2016;375(18):1726-1737.

Part of the larger PROMISE (Promoting Maternal and Infant Survival Everywhere) trial, a study by Fowler and colleagues compared the relative efficacy and safety of various proven ART strategies for prevention of mother-to-child transmission of HIV infection in women with relatively high CD4 counts.

Details of the study

The trial was conducted at 14 sites in 7 countries. Patients were stratified according to HBV coinfection status and country of origin. The primary efficacy outcome was frequency of early infant HIV infection.

Women were randomly assigned to 1 of 3 treatment categories:

• zidovudine alone (zidovudine plus a single intrapartum dose of nevirapine, followed by 6 to 14 days of tenofovir plus emtricitabine postpartum)  
• zidovudine-based ART (zidovudine in combination with lamivudine and lopinavir-ritonavir)  
• tenofovir-based ART (tenofovir in combination with emtricitabine and lopinavir-ritonavir). 

All regimens were continued through 6 to 14 days postpartum. All infants received nevirapine at birth and in the immediate postpartum period.

Two trial periods. During period 1 (April 2011-September 2012), safety data on tenofovir in pregnancy were limited. Women without HBV coinfection were assigned only to zidovudine alone or zidovudine-based ART. During period 2 (October 2012-October 2014), since more information about tenofovir use in pregnancy was available, the study protocol was modified to allow women to be assigned to any of the 3 regimens, regardless of their HBV status.

Inclusion criteria were as follows: CD4 count of at least 350 cells/mm3 (or country-specific threshold for initiating triple-drug ART, if that threshold was higher), gestation of at least 14 weeks and not in labor, no previous use of triple-drug ART, no clinical or immune-related indication for triple-drug ART, hemoglobin level of at least 6.5 g/dL, an absolute neutrophil count of at least 750 cells/mm3, an alanine aminotransferase level of less than 2.5 times the upper limit of normal range, an estimated creatinine clearance of greater than 60 mL/min, and no serious pregnancy complications. Patients were excluded if they had active tuberculosis, HBV infection requiring treatment, a structural or conduction heart defect, or a fetus with a serious congenital malformation.

Primary outcomes. The primary efficacy outcome was early infant HIV infection, defined as a positive infant HIV nucleic acid test result at birth or at 1 week postpartum. The primary safety outcome was a composite of adverse events.

Adverse events in mothers were defined as hematologic abnormalities, abnormal blood chemical values, or abnormal signs/symptoms during pregnancy through 1 week postpartum. Severe pregnancy composite outcomes were low birth weight (<2,500 g), preterm delivery before 37 weeks' gestation, spontaneous abortion (<20 weeks), stillbirth (≥20 weeks), or congenital anomaly. Adverse events in infants were defined as death from any cause, hematologic abnormalities or abnormal blood chemical values, and abnormal signs/symptoms through 1 week postpartum.

A total of 3,490 mother-infant sets were included in the analysis (2,261 during trial period 1 and 1,229 during trial period 2). Baseline maternal characteristics were well balanced between groups. Most women were African, young (median age, 26 years), and asymptomatic.

Related article:
2016 Update on infectious disease

Study results

The combined maternal ART-treated groups had significantly lower rates of early transmission of HIV infection compared with the zidovudine-alone group (0.5% vs 1.8%, -1.3 percentage points; CI, -2.1 to -0.4). The zidovudine-based ART-treated group had a significantly higher rate of infant HIV-free survival through postpartum week 1 than did the zidovudine-alone group (P = .001) or the tenofovir-based ART group (P = .002).

When examining trial periods 1 and 2 combined, the zidovudine-based ART group experienced significantly higher rates of any adverse event than those receiving zidovudine alone (21.1% vs 17.3%, P = .008) and higher rates of abnormal blood chemical values (5.8% vs 1.3%, P<.001). During period 2 alone, the tenofovir-based ART group had significantly higher rates of abnormal blood chemical values than did the zidovudine-alone group (2.9% vs 0.8%, P = .03). There were no significant differences between the 2 ART treatment groups. No maternal deaths occurred during the study, and the trial-drug discontinuation rate was low (2%-5%) and did not vary among the 3 groups.

During trial periods 1 and 2, the zidovudine-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (40% vs 27.5%, P<.001). These included low birth weight less than 2,500 g (23% vs 12%) and preterm delivery before 37 weeks (20.5% vs 13.1%). During trial period 2, the tenofovir-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (34.7% vs 27.2%, P = .04). There were no significant differences for any outcome between the 2 ART-treated groups, and there were no significant differences in stillbirth or spontaneous abortion and congenital anomalies among the 3 groups.

Regarding severe pregnancy outcomes, there were no significant differences (composite or individual) between the zidovudine-based ART group and the zidovudine-alone group. The tenofovir-based ART group experienced significantly higher rates of composite severe adverse pregnancy outcomes compared with the zidovudine-based ART group (9.2% vs 4.3%, P = .02), and very preterm birth before 34 weeks (6.0% vs 2.6%, P = .04).

Infant safety outcomes were also examined. There were no significant differences for composite or individual adverse neonatal outcomes other than death. The tenofovir-based ART group experienced a significantly higher rate of infant death than did the zidovudine-based ART group (4.4% vs 0.6%, P<.001). However, a post hoc analysis suggested that extreme prematurity contributed to the infant mortality.

Limitations of the study

This study had minor limitations. It divided patients into only 2 major categories with respect to gestational age--more than or less than 34 weeks. Some maternal medical conditions, such as malaria, were not controlled for. In addition, breastfeeding and formula feeding were combined for analysis, and we know that breastfeeding would inherently confer a higher risk of HIV transmission. 

Nevertheless, this study was thoughtfully designed and carefully conducted, and the results are of significant global impact.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

In this Update we review the results of 4 recent investigations that have important implications:

• the first analysis of the US Zika Virus Infection in Pregnancy Registry
• a study revealing an improved antibiotic regimen to prevent postcesarean infection
• an important new methodology for reducing the rate of perinatal transmission of hepatitis B virus (HBV) infection
• the risks and benefits of combination antiretroviral therapy (ART) in pregnancy.

Zika virus-associated birth defect rates similar regardless of symptom presence; first-trimester exposure has highest rate of anomalies

Honein MA, Dawson AL, Petersen EE, et al; US Zika Pregnancy Registry Collaboration. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA. 2017;317(1):59-68.

Honein and colleagues provide a summary of the data from the US Zika Virus in Pregnancy Registry (a collaboration between the Centers for Disease Control and Prevention and state and local health departments), estimating the proportion of fetuses and infants with birth defects based on maternal symptoms of Zika virus infection and  trimester of possible infection.

Related article:
Zika virus: Counseling considerations for this emerging perinatal threat

Details of the study

The authors evaluated the outcomes of 442 women who had laboratory evidence of a possible Zika virus infection during pregnancy. Overall, 26 infants (6%; 95% confidence interval (CI), 4%-8%) had evidence of birth defects related to the Zika virus. Of note, abnormalities were detected in 16 of the 271 children (6%; 95% CI, 4%-9%) born to women who were asymptomatic and 10 of 167 (6%; 95% CI, 3%-11%) children delivered to women with symptomatic infections. 

The most common birth defect was microcephaly, although other serious central nervous system abnormalities were noted as well. Nine of 85 women (11%; 95% CI, 6%-19%) who had exposure only during the first trimester had infants with birth defects. There were no documented abnormalities in infants born to mothers who developed Zika virus infection only in the second or third trimester. 

Related article:
Zika virus update: A rapidly moving target

Key study findings

This article is important for several reasons. First, the authors describe the largest series of pregnant women in the United States with Zika virus infection. All of these patients developed Zika virus infection as a result of foreign travel or exposure to sexual partners who had traveled to Zika virus endemic areas. Second, the authors confirmed findings that previously had been based only on mathematical models rather than on actual case series. Specifically, they demonstrated that the risk of a serious birth defect following first-trimester exposure to Zika virus infection was approximately 11%, with a 95% CI that extended from 6% to 19%. Finally, Honein and colleagues highlighted the key fact that the risk of a serious birth defect was comparable in mothers who had either an asymptomatic or a symptomatic infection, a finding that seems somewhat counterintuitive.

Read about prophylaxis for postcesarean infection

Two antibiotics before cesarean delivery reduce infection rates further than one agent

Tita AT, Szychowski JM, Boggess K, et al; for the C/SOAP Trial Consortium. Adjunctive azithromycin prophylaxis for cesarean delivery. N Engl J Med. 2016;375(13):1231-1241.

Tita and colleagues reported the results of a multicenter trial that was designed to assess whether a combination of 2 antibiotics, including one that specifically targets ureaplasma species, provided more effective prophylaxis against postcesarean infection than single-agent prophylaxis.

Details of the study

The Cesarean Section Optimal Antibiotic Prophylaxis (C/SOAP) trial was conducted at 14 centers in the United States and included 2,013 women who were at least at 24 weeks' gestation and who had a cesarean delivery during labor or after membrane rupture.

The authors randomly assigned 1,019 women to receive 500 mg of intravenous azithromycin plus conventional single-agent prophylaxis (usually cefazolin) and 994 women to receive a placebo plus conventional prophylaxis. The primary outcome was the composite of endometritis, wound infection, or other infection occurring within 6 weeks.

The authors observed that the primary outcome occurred in 62 women (6.1%) who received azithromycin plus conventional prophylaxis and in 119 women (12%) who received only single-agent prophylaxis. The relative risk of developing a postoperative infection was 0.51 in women who received the combined therapy. There were significant differences between the 2 groups in both the rates of endometritis (3.8% vs 6.1%, P = .02) and wound infection (2.4% vs 6.6%, P<.001). There were no differences between the groups in the frequency of the secondary neonatal composite outcome, which included neonatal death and serious neonatal complications.

Related article:
Preventing infection after cesarean delivery: 5 more evidence-based measures to consider

Efficacy of dual-agent prophylaxis

At present, the standard of care is to administer prophylactic antibiotics to all women having cesarean delivery, including women having a scheduled cesarean in the absence of labor or ruptured membranes. Multiple studies have shown clearly that prophylaxis reduces the frequency of endometritis and, in high-risk patient populations, wound infection, and that prophylaxis is most beneficial when administered prior to the time the surgical incision is made. The most commonly used drug for prophylaxis is cefazolin, a first-generation cephalosporin. The usual recommended dose is 2 g, administered immediately prior to surgery.^3,4

Although most centers in the United States traditionally have used just a single antibiotic for prophylaxis, selected recent reports indicate that expanding the spectrum of activity of prophylactic antibiotics can result in additional beneficial effects. Specifically, Tita and colleagues evaluated an indigent patient population with an inherently high rate of postoperative infection.⁵ They showed that adding azithromycin 500 mg to cefazolin significantly reduced the rate of postcesarean endometritis. In a follow-up report from the same institution, Tita and colleagues demonstrated that adding azithromycin also significantly reduced the frequency of wound infection.⁶ Of note, in both these investigations, the antibiotics were administered after cord clamping. In a subsequent report, Ward and Duff showed that the combination of azithromycin plus cefazolin administered preoperatively resulted in a combined rate of endometritis and wound infection that was less than 3%.⁷

Related article:
Preventing infection after cesarean delivery: Evidence-based guidance

C/SOAP trial confirmed lower infection rates with combined regimen

Results of the present study confirm the findings of these 3 investigations. The trial included a large sample size. The study was carefully designed, and the end points were clearly defined. It included only patients at increased risk for postoperative infection by virtue of being in labor or having ruptured membranes at the time of cesarean delivery. Patients who received standard prophylaxis, usually cefazolin, plus azithromycin had a significantly lower risk of postcesarean endometritis and wound infection compared with patients who received a single antibiotic. The overall risk of infection was reduced by an impressive 50%.  
 

Read about reducing HBV transmission

Tenofovir treatment in pregnant women with HBV reduces vertical transmission

Pan CQ, Duan Z, Dai E, et al; China Study Group for the Mother-to-Child Transmission of Hepatitis B. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016;374(24):2324-2334.

A multicenter, open-label, randomized, parallel-group investigation was conducted from March 2012 to June 2013 at academic tertiary care centers in 5 geographic regions of China. Two hundred mothers, who were positive for both hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) and who had HBV DNA concentrations of 200,000 IU/mL or greater, were randomly assigned in a 1:1 ratio to either tenofovir or to usual treatment. Exclusion criteria were coexistent viral infections or medical conditions, renal failure, laboratory abnormalities, fetal deformities, and use of many medications.

Related article:
5 ways to reduce infection risk during pregnancy

Details of the study

Women in the active treatment group received tenofovir 300 mg by mouth daily from 30 to 32 weeks' gestation until postpartum week 4. Patients were monitored every 4 weeks in the antepartum period for adverse events and laboratory abnormalities. In the postpartum period, mother-infant dyads were evaluated at weeks 4, 12, 24, and 28.

Primary outcomes were the rates of mother-to-child transmission and birth defects with, or without, tenofovir exposure. Secondary outcomes were the percentage of mothers who had an HBV DNA serum concentration of less than 200,000 IU/mL at delivery and the percentage of mothers with HBeAg or HBsAg loss or seroconversion at postpartum week 28. Safety outcomes included the adverse event profile of tenofovir in mothers and safety events in the mother-infant dyads. These outcomes encompassed  all adverse events and drug discontinuations in patients who received at least one dose of tenofovir.

Sixty-eight percent of mothers in the tenofovir group, compared with 2% of mothers in the control group, had HBV levels less than 200,000 IU/mL at delivery (P<.001). The rate of mother-to-child HBV transmission at postpartum week 28 was lower in the tenofovir group. In the intention-to-treat analysis, the rate was 5% (95% CI, 1-10; 5 of 97 infants) in the tenofovir group versus 18% (95% CI, 10-26; 18 of 100 infants) in the control group (P = .007). In the per-protocol analysis, the rate was 0% (95% CI, 0-3; 0 of 92 infants) in the tenofovir group versus 7% (95% CI, 2-12; 6 of 88 infants) in the control group (P = .01). Maternal and infant safety profiles were similar between the 2 groups, with the exception of elevated creatinine kinase and alanine aminotransferase levels in mothers treated with tenofovir. Maternal HBV serologic titers did not differ significantly between the 2 groups.

Study strengths and limitations

This study's strengths include a multicenter, randomized controlled design, with strict inclusion and exclusion criteria. The results are clinically relevant and of global impact, with potential to decrease morbidity and  mortality from HBV infection in children born to infected mothers. 

A limitation, however, is that the study was probably underpowered to detect small differences in the rate of birth defects between the tenofovir and usual-care treatment groups. Additionally, some patients ceased taking tenofovir in the postpartum time period. Abrupt cessation may be associated with acute, severe HBV exacerbation.  

Benefits of ART for reducing mother-to-baby HIV transmission outweigh higher risk of adverse outcomes

Fowler MG, Qin M, Fiscus SA, et al; IMPAACT 1077BF/1077FF PROMISE Study Team. Benefits and risks of antiretroviral therapy for perinatal HIV prevention. N Engl J Med. 2016;375(18):1726-1737.

Part of the larger PROMISE (Promoting Maternal and Infant Survival Everywhere) trial, a study by Fowler and colleagues compared the relative efficacy and safety of various proven ART strategies for prevention of mother-to-child transmission of HIV infection in women with relatively high CD4 counts.

Details of the study

The trial was conducted at 14 sites in 7 countries. Patients were stratified according to HBV coinfection status and country of origin. The primary efficacy outcome was frequency of early infant HIV infection.

Women were randomly assigned to 1 of 3 treatment categories:

• zidovudine alone (zidovudine plus a single intrapartum dose of nevirapine, followed by 6 to 14 days of tenofovir plus emtricitabine postpartum)  
• zidovudine-based ART (zidovudine in combination with lamivudine and lopinavir-ritonavir)  
• tenofovir-based ART (tenofovir in combination with emtricitabine and lopinavir-ritonavir). 

All regimens were continued through 6 to 14 days postpartum. All infants received nevirapine at birth and in the immediate postpartum period.

Two trial periods. During period 1 (April 2011-September 2012), safety data on tenofovir in pregnancy were limited. Women without HBV coinfection were assigned only to zidovudine alone or zidovudine-based ART. During period 2 (October 2012-October 2014), since more information about tenofovir use in pregnancy was available, the study protocol was modified to allow women to be assigned to any of the 3 regimens, regardless of their HBV status.

Inclusion criteria were as follows: CD4 count of at least 350 cells/mm3 (or country-specific threshold for initiating triple-drug ART, if that threshold was higher), gestation of at least 14 weeks and not in labor, no previous use of triple-drug ART, no clinical or immune-related indication for triple-drug ART, hemoglobin level of at least 6.5 g/dL, an absolute neutrophil count of at least 750 cells/mm3, an alanine aminotransferase level of less than 2.5 times the upper limit of normal range, an estimated creatinine clearance of greater than 60 mL/min, and no serious pregnancy complications. Patients were excluded if they had active tuberculosis, HBV infection requiring treatment, a structural or conduction heart defect, or a fetus with a serious congenital malformation.

Primary outcomes. The primary efficacy outcome was early infant HIV infection, defined as a positive infant HIV nucleic acid test result at birth or at 1 week postpartum. The primary safety outcome was a composite of adverse events.

Adverse events in mothers were defined as hematologic abnormalities, abnormal blood chemical values, or abnormal signs/symptoms during pregnancy through 1 week postpartum. Severe pregnancy composite outcomes were low birth weight (<2,500 g), preterm delivery before 37 weeks' gestation, spontaneous abortion (<20 weeks), stillbirth (≥20 weeks), or congenital anomaly. Adverse events in infants were defined as death from any cause, hematologic abnormalities or abnormal blood chemical values, and abnormal signs/symptoms through 1 week postpartum.

A total of 3,490 mother-infant sets were included in the analysis (2,261 during trial period 1 and 1,229 during trial period 2). Baseline maternal characteristics were well balanced between groups. Most women were African, young (median age, 26 years), and asymptomatic.

Related article:
2016 Update on infectious disease

Study results

The combined maternal ART-treated groups had significantly lower rates of early transmission of HIV infection compared with the zidovudine-alone group (0.5% vs 1.8%, -1.3 percentage points; CI, -2.1 to -0.4). The zidovudine-based ART-treated group had a significantly higher rate of infant HIV-free survival through postpartum week 1 than did the zidovudine-alone group (P = .001) or the tenofovir-based ART group (P = .002).

When examining trial periods 1 and 2 combined, the zidovudine-based ART group experienced significantly higher rates of any adverse event than those receiving zidovudine alone (21.1% vs 17.3%, P = .008) and higher rates of abnormal blood chemical values (5.8% vs 1.3%, P<.001). During period 2 alone, the tenofovir-based ART group had significantly higher rates of abnormal blood chemical values than did the zidovudine-alone group (2.9% vs 0.8%, P = .03). There were no significant differences between the 2 ART treatment groups. No maternal deaths occurred during the study, and the trial-drug discontinuation rate was low (2%-5%) and did not vary among the 3 groups.

During trial periods 1 and 2, the zidovudine-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (40% vs 27.5%, P<.001). These included low birth weight less than 2,500 g (23% vs 12%) and preterm delivery before 37 weeks (20.5% vs 13.1%). During trial period 2, the tenofovir-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (34.7% vs 27.2%, P = .04). There were no significant differences for any outcome between the 2 ART-treated groups, and there were no significant differences in stillbirth or spontaneous abortion and congenital anomalies among the 3 groups.

Regarding severe pregnancy outcomes, there were no significant differences (composite or individual) between the zidovudine-based ART group and the zidovudine-alone group. The tenofovir-based ART group experienced significantly higher rates of composite severe adverse pregnancy outcomes compared with the zidovudine-based ART group (9.2% vs 4.3%, P = .02), and very preterm birth before 34 weeks (6.0% vs 2.6%, P = .04).

Infant safety outcomes were also examined. There were no significant differences for composite or individual adverse neonatal outcomes other than death. The tenofovir-based ART group experienced a significantly higher rate of infant death than did the zidovudine-based ART group (4.4% vs 0.6%, P<.001). However, a post hoc analysis suggested that extreme prematurity contributed to the infant mortality.

Limitations of the study

This study had minor limitations. It divided patients into only 2 major categories with respect to gestational age--more than or less than 34 weeks. Some maternal medical conditions, such as malaria, were not controlled for. In addition, breastfeeding and formula feeding were combined for analysis, and we know that breastfeeding would inherently confer a higher risk of HIV transmission. 

Nevertheless, this study was thoughtfully designed and carefully conducted, and the results are of significant global impact.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

In this Update we review the results of 4 recent investigations that have important implications:

• the first analysis of the US Zika Virus Infection in Pregnancy Registry
• a study revealing an improved antibiotic regimen to prevent postcesarean infection
• an important new methodology for reducing the rate of perinatal transmission of hepatitis B virus (HBV) infection
• the risks and benefits of combination antiretroviral therapy (ART) in pregnancy.

Zika virus-associated birth defect rates similar regardless of symptom presence; first-trimester exposure has highest rate of anomalies

Honein MA, Dawson AL, Petersen EE, et al; US Zika Pregnancy Registry Collaboration. Birth defects among fetuses and infants of US women with evidence of possible Zika virus infection during pregnancy. JAMA. 2017;317(1):59-68.

Honein and colleagues provide a summary of the data from the US Zika Virus in Pregnancy Registry (a collaboration between the Centers for Disease Control and Prevention and state and local health departments), estimating the proportion of fetuses and infants with birth defects based on maternal symptoms of Zika virus infection and  trimester of possible infection.

Related article:
Zika virus: Counseling considerations for this emerging perinatal threat

Details of the study

The authors evaluated the outcomes of 442 women who had laboratory evidence of a possible Zika virus infection during pregnancy. Overall, 26 infants (6%; 95% confidence interval (CI), 4%-8%) had evidence of birth defects related to the Zika virus. Of note, abnormalities were detected in 16 of the 271 children (6%; 95% CI, 4%-9%) born to women who were asymptomatic and 10 of 167 (6%; 95% CI, 3%-11%) children delivered to women with symptomatic infections. 

The most common birth defect was microcephaly, although other serious central nervous system abnormalities were noted as well. Nine of 85 women (11%; 95% CI, 6%-19%) who had exposure only during the first trimester had infants with birth defects. There were no documented abnormalities in infants born to mothers who developed Zika virus infection only in the second or third trimester. 

Related article:
Zika virus update: A rapidly moving target

Key study findings

This article is important for several reasons. First, the authors describe the largest series of pregnant women in the United States with Zika virus infection. All of these patients developed Zika virus infection as a result of foreign travel or exposure to sexual partners who had traveled to Zika virus endemic areas. Second, the authors confirmed findings that previously had been based only on mathematical models rather than on actual case series. Specifically, they demonstrated that the risk of a serious birth defect following first-trimester exposure to Zika virus infection was approximately 11%, with a 95% CI that extended from 6% to 19%. Finally, Honein and colleagues highlighted the key fact that the risk of a serious birth defect was comparable in mothers who had either an asymptomatic or a symptomatic infection, a finding that seems somewhat counterintuitive.

Read about prophylaxis for postcesarean infection

Two antibiotics before cesarean delivery reduce infection rates further than one agent

Tita AT, Szychowski JM, Boggess K, et al; for the C/SOAP Trial Consortium. Adjunctive azithromycin prophylaxis for cesarean delivery. N Engl J Med. 2016;375(13):1231-1241.

Tita and colleagues reported the results of a multicenter trial that was designed to assess whether a combination of 2 antibiotics, including one that specifically targets ureaplasma species, provided more effective prophylaxis against postcesarean infection than single-agent prophylaxis.

Details of the study

The Cesarean Section Optimal Antibiotic Prophylaxis (C/SOAP) trial was conducted at 14 centers in the United States and included 2,013 women who were at least at 24 weeks' gestation and who had a cesarean delivery during labor or after membrane rupture.

The authors randomly assigned 1,019 women to receive 500 mg of intravenous azithromycin plus conventional single-agent prophylaxis (usually cefazolin) and 994 women to receive a placebo plus conventional prophylaxis. The primary outcome was the composite of endometritis, wound infection, or other infection occurring within 6 weeks.

The authors observed that the primary outcome occurred in 62 women (6.1%) who received azithromycin plus conventional prophylaxis and in 119 women (12%) who received only single-agent prophylaxis. The relative risk of developing a postoperative infection was 0.51 in women who received the combined therapy. There were significant differences between the 2 groups in both the rates of endometritis (3.8% vs 6.1%, P = .02) and wound infection (2.4% vs 6.6%, P<.001). There were no differences between the groups in the frequency of the secondary neonatal composite outcome, which included neonatal death and serious neonatal complications.

Related article:
Preventing infection after cesarean delivery: 5 more evidence-based measures to consider

Efficacy of dual-agent prophylaxis

At present, the standard of care is to administer prophylactic antibiotics to all women having cesarean delivery, including women having a scheduled cesarean in the absence of labor or ruptured membranes. Multiple studies have shown clearly that prophylaxis reduces the frequency of endometritis and, in high-risk patient populations, wound infection, and that prophylaxis is most beneficial when administered prior to the time the surgical incision is made. The most commonly used drug for prophylaxis is cefazolin, a first-generation cephalosporin. The usual recommended dose is 2 g, administered immediately prior to surgery.^3,4

Although most centers in the United States traditionally have used just a single antibiotic for prophylaxis, selected recent reports indicate that expanding the spectrum of activity of prophylactic antibiotics can result in additional beneficial effects. Specifically, Tita and colleagues evaluated an indigent patient population with an inherently high rate of postoperative infection.⁵ They showed that adding azithromycin 500 mg to cefazolin significantly reduced the rate of postcesarean endometritis. In a follow-up report from the same institution, Tita and colleagues demonstrated that adding azithromycin also significantly reduced the frequency of wound infection.⁶ Of note, in both these investigations, the antibiotics were administered after cord clamping. In a subsequent report, Ward and Duff showed that the combination of azithromycin plus cefazolin administered preoperatively resulted in a combined rate of endometritis and wound infection that was less than 3%.⁷

Related article:
Preventing infection after cesarean delivery: Evidence-based guidance

C/SOAP trial confirmed lower infection rates with combined regimen

Results of the present study confirm the findings of these 3 investigations. The trial included a large sample size. The study was carefully designed, and the end points were clearly defined. It included only patients at increased risk for postoperative infection by virtue of being in labor or having ruptured membranes at the time of cesarean delivery. Patients who received standard prophylaxis, usually cefazolin, plus azithromycin had a significantly lower risk of postcesarean endometritis and wound infection compared with patients who received a single antibiotic. The overall risk of infection was reduced by an impressive 50%.  
 

Read about reducing HBV transmission

Tenofovir treatment in pregnant women with HBV reduces vertical transmission

Pan CQ, Duan Z, Dai E, et al; China Study Group for the Mother-to-Child Transmission of Hepatitis B. Tenofovir to prevent hepatitis B transmission in mothers with high viral load. N Engl J Med. 2016;374(24):2324-2334.

A multicenter, open-label, randomized, parallel-group investigation was conducted from March 2012 to June 2013 at academic tertiary care centers in 5 geographic regions of China. Two hundred mothers, who were positive for both hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) and who had HBV DNA concentrations of 200,000 IU/mL or greater, were randomly assigned in a 1:1 ratio to either tenofovir or to usual treatment. Exclusion criteria were coexistent viral infections or medical conditions, renal failure, laboratory abnormalities, fetal deformities, and use of many medications.

Related article:
5 ways to reduce infection risk during pregnancy

Details of the study

Women in the active treatment group received tenofovir 300 mg by mouth daily from 30 to 32 weeks' gestation until postpartum week 4. Patients were monitored every 4 weeks in the antepartum period for adverse events and laboratory abnormalities. In the postpartum period, mother-infant dyads were evaluated at weeks 4, 12, 24, and 28.

Primary outcomes were the rates of mother-to-child transmission and birth defects with, or without, tenofovir exposure. Secondary outcomes were the percentage of mothers who had an HBV DNA serum concentration of less than 200,000 IU/mL at delivery and the percentage of mothers with HBeAg or HBsAg loss or seroconversion at postpartum week 28. Safety outcomes included the adverse event profile of tenofovir in mothers and safety events in the mother-infant dyads. These outcomes encompassed  all adverse events and drug discontinuations in patients who received at least one dose of tenofovir.

Sixty-eight percent of mothers in the tenofovir group, compared with 2% of mothers in the control group, had HBV levels less than 200,000 IU/mL at delivery (P<.001). The rate of mother-to-child HBV transmission at postpartum week 28 was lower in the tenofovir group. In the intention-to-treat analysis, the rate was 5% (95% CI, 1-10; 5 of 97 infants) in the tenofovir group versus 18% (95% CI, 10-26; 18 of 100 infants) in the control group (P = .007). In the per-protocol analysis, the rate was 0% (95% CI, 0-3; 0 of 92 infants) in the tenofovir group versus 7% (95% CI, 2-12; 6 of 88 infants) in the control group (P = .01). Maternal and infant safety profiles were similar between the 2 groups, with the exception of elevated creatinine kinase and alanine aminotransferase levels in mothers treated with tenofovir. Maternal HBV serologic titers did not differ significantly between the 2 groups.

Study strengths and limitations

This study's strengths include a multicenter, randomized controlled design, with strict inclusion and exclusion criteria. The results are clinically relevant and of global impact, with potential to decrease morbidity and  mortality from HBV infection in children born to infected mothers. 

A limitation, however, is that the study was probably underpowered to detect small differences in the rate of birth defects between the tenofovir and usual-care treatment groups. Additionally, some patients ceased taking tenofovir in the postpartum time period. Abrupt cessation may be associated with acute, severe HBV exacerbation.  

Benefits of ART for reducing mother-to-baby HIV transmission outweigh higher risk of adverse outcomes

Fowler MG, Qin M, Fiscus SA, et al; IMPAACT 1077BF/1077FF PROMISE Study Team. Benefits and risks of antiretroviral therapy for perinatal HIV prevention. N Engl J Med. 2016;375(18):1726-1737.

Part of the larger PROMISE (Promoting Maternal and Infant Survival Everywhere) trial, a study by Fowler and colleagues compared the relative efficacy and safety of various proven ART strategies for prevention of mother-to-child transmission of HIV infection in women with relatively high CD4 counts.

Details of the study

The trial was conducted at 14 sites in 7 countries. Patients were stratified according to HBV coinfection status and country of origin. The primary efficacy outcome was frequency of early infant HIV infection.

Women were randomly assigned to 1 of 3 treatment categories:

• zidovudine alone (zidovudine plus a single intrapartum dose of nevirapine, followed by 6 to 14 days of tenofovir plus emtricitabine postpartum)  
• zidovudine-based ART (zidovudine in combination with lamivudine and lopinavir-ritonavir)  
• tenofovir-based ART (tenofovir in combination with emtricitabine and lopinavir-ritonavir). 

All regimens were continued through 6 to 14 days postpartum. All infants received nevirapine at birth and in the immediate postpartum period.

Two trial periods. During period 1 (April 2011-September 2012), safety data on tenofovir in pregnancy were limited. Women without HBV coinfection were assigned only to zidovudine alone or zidovudine-based ART. During period 2 (October 2012-October 2014), since more information about tenofovir use in pregnancy was available, the study protocol was modified to allow women to be assigned to any of the 3 regimens, regardless of their HBV status.

Inclusion criteria were as follows: CD4 count of at least 350 cells/mm3 (or country-specific threshold for initiating triple-drug ART, if that threshold was higher), gestation of at least 14 weeks and not in labor, no previous use of triple-drug ART, no clinical or immune-related indication for triple-drug ART, hemoglobin level of at least 6.5 g/dL, an absolute neutrophil count of at least 750 cells/mm3, an alanine aminotransferase level of less than 2.5 times the upper limit of normal range, an estimated creatinine clearance of greater than 60 mL/min, and no serious pregnancy complications. Patients were excluded if they had active tuberculosis, HBV infection requiring treatment, a structural or conduction heart defect, or a fetus with a serious congenital malformation.

Primary outcomes. The primary efficacy outcome was early infant HIV infection, defined as a positive infant HIV nucleic acid test result at birth or at 1 week postpartum. The primary safety outcome was a composite of adverse events.

Adverse events in mothers were defined as hematologic abnormalities, abnormal blood chemical values, or abnormal signs/symptoms during pregnancy through 1 week postpartum. Severe pregnancy composite outcomes were low birth weight (<2,500 g), preterm delivery before 37 weeks' gestation, spontaneous abortion (<20 weeks), stillbirth (≥20 weeks), or congenital anomaly. Adverse events in infants were defined as death from any cause, hematologic abnormalities or abnormal blood chemical values, and abnormal signs/symptoms through 1 week postpartum.

A total of 3,490 mother-infant sets were included in the analysis (2,261 during trial period 1 and 1,229 during trial period 2). Baseline maternal characteristics were well balanced between groups. Most women were African, young (median age, 26 years), and asymptomatic.

Related article:
2016 Update on infectious disease

Study results

The combined maternal ART-treated groups had significantly lower rates of early transmission of HIV infection compared with the zidovudine-alone group (0.5% vs 1.8%, -1.3 percentage points; CI, -2.1 to -0.4). The zidovudine-based ART-treated group had a significantly higher rate of infant HIV-free survival through postpartum week 1 than did the zidovudine-alone group (P = .001) or the tenofovir-based ART group (P = .002).

When examining trial periods 1 and 2 combined, the zidovudine-based ART group experienced significantly higher rates of any adverse event than those receiving zidovudine alone (21.1% vs 17.3%, P = .008) and higher rates of abnormal blood chemical values (5.8% vs 1.3%, P<.001). During period 2 alone, the tenofovir-based ART group had significantly higher rates of abnormal blood chemical values than did the zidovudine-alone group (2.9% vs 0.8%, P = .03). There were no significant differences between the 2 ART treatment groups. No maternal deaths occurred during the study, and the trial-drug discontinuation rate was low (2%-5%) and did not vary among the 3 groups.

During trial periods 1 and 2, the zidovudine-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (40% vs 27.5%, P<.001). These included low birth weight less than 2,500 g (23% vs 12%) and preterm delivery before 37 weeks (20.5% vs 13.1%). During trial period 2, the tenofovir-based ART group had significantly higher rates of adverse pregnancy outcomes than did the zidovudine-alone group (34.7% vs 27.2%, P = .04). There were no significant differences for any outcome between the 2 ART-treated groups, and there were no significant differences in stillbirth or spontaneous abortion and congenital anomalies among the 3 groups.

Regarding severe pregnancy outcomes, there were no significant differences (composite or individual) between the zidovudine-based ART group and the zidovudine-alone group. The tenofovir-based ART group experienced significantly higher rates of composite severe adverse pregnancy outcomes compared with the zidovudine-based ART group (9.2% vs 4.3%, P = .02), and very preterm birth before 34 weeks (6.0% vs 2.6%, P = .04).

Infant safety outcomes were also examined. There were no significant differences for composite or individual adverse neonatal outcomes other than death. The tenofovir-based ART group experienced a significantly higher rate of infant death than did the zidovudine-based ART group (4.4% vs 0.6%, P<.001). However, a post hoc analysis suggested that extreme prematurity contributed to the infant mortality.

Limitations of the study

This study had minor limitations. It divided patients into only 2 major categories with respect to gestational age--more than or less than 34 weeks. Some maternal medical conditions, such as malaria, were not controlled for. In addition, breastfeeding and formula feeding were combined for analysis, and we know that breastfeeding would inherently confer a higher risk of HIV transmission. 

Nevertheless, this study was thoughtfully designed and carefully conducted, and the results are of significant global impact.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

INTRODUCTION

Lung cancer is the second most common type of cancer in the United States, with 222,500 estimated new cases in 2017, according to the American Cancer Society.¹ However, it is by far the number one cause of death due to cancer, with an estimated 155,870 lung cancer–related deaths occurring in 2017, which is higher than the number of deaths due to breast cancer, prostate cancer, and colorectal cancer combined.^1,2 Despite slightly decreasing incidence and mortality over the past decade, largely due to smoking cessation, the 5-year survival rate of lung cancer remains dismal at approximately 18%.^2–4

Non-small cell lung cancer (NSCLC) accounts for 80% to 85% of all lung cancer cases.⁴ Traditionally, it is further divided based on histology: adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and not otherwise specified.⁵ Chemotherapy had been the cornerstone of treatment for stage IV NSCLC. It is not target-specific and is most effective against rapidly growing cells. Common adverse effects include alopecia, nausea/vomiting, myelosuppression, cardiotoxicity, neuropathy, and nephrotoxicity. However, this paradigm has shifted following the discovery of mutations of the epidermal growth factor receptor (EGFR) gene as an oncogenic driver that confers sensitivity to small molecule tyrosine kinase inhibitors (TKIs) targeting EGFR.⁶ The EGFR inhibitors are given orally and have a spectrum of toxicities (eg, such as rash, diarrhea, and elevated transaminases) different from that of systemic chemotherapy, which is often administered intravenously. Following the discovery of EGFR mutations, rearrangements of the anaplastic lymphoma kinase (ALK) gene⁷ and ROS1 gene⁸ were identified as targetable driver mutations in NSCLC. The frequency of both rearrangements is lower than that of EGFR mutations. Additionally, BRAF V600E mutation has been identified in NSCLC.^9–12 This activation mutation is commonly seen in melanoma. Agents that have already been approved for the treatment of melanoma with the BRAF V600E mutation are being tested in NSCLC patients with this mutation.^13–16

Given the effectiveness and tolerability of targeted therapy, identifying this distinct molecular subset of NSCLC patients is critical in treatment. Currently, molecular testing is mandatory in all stage IV patients with non-squamous cell carcinoma, as a preponderance of patients with driver mutations have this histology subtype.^5,17–19 For patients with squamous cell carcinoma, molecular testing should be considered if the biopsy specimen is small, there is mixed histology, or the patient is a nonsmoker.^5,20 Several techniques are commonly utilized in detecting these genetic alterations. EGFR mutation can be detected by polymerase chain reaction (PCR), ALK or ROS1 rearrangement can be detected by fluorescence in-situ hybridization (FISH), and immunohistochemistry (IHC) can also be used to detect ALK rearrangement. The current guideline is to use comprehensive genomic profiling to capture all the potential molecular targets simultaneously instead of running stepwise tests just for EGFR, ALK, and ROS1.⁵BRAF V600E mutation,^13–16 MET exon 14 skipping mutation,^21–24 RET rearrangements,^25–27 and HER2 mutations^28–30 are among the emergent genetic alterations with various responses to targeted therapy.³¹ Some of these targeted agents have been approved for other types of malignancy, and others are still in the development phase.

Several initiatives worldwide have reported better outcomes of patients with driver mutations treated with targeted therapy. For instance, the Lung Cancer Mutation Consortium in the United States demonstrated that the median survival of patients without driver mutations, with drivers mutations but not treated with targeted therapy, and with driver mutations and treated with targeted therapy was 2.08 years, 2.38 years, and 3.49 years, respectively.³² The French Cooperative Thoracic Intergroup-French National Cancer Institute demonstrated that the median survival for patients with driver mutations versus those without driver mutations was 16.5 months versus 11.8 months.³³ The Spanish Lung Cancer Group demonstrated that the overall survival (OS) for patients with EGFR mutations treated with erlotinib was 27 months.³⁴ The mutations in lung cancer, their frequencies, and the downstream signaling pathways are depicted in the Figure.³⁵

In this article, we discuss targeted therapy for patients with EGFR mutations, ALK rearrangements, ROS1 rearrangements, and BRAF V600E mutation. We also discuss the management of patients with EGFR mutations who develop a secondary mutation after TKI therapy. Almost all of the targeted agents discussed herein have been approved by the US Food and Drug Administration (FDA), so they are considered standard of care. All available phase 3 trials pertinent to these targeted therapies are included in the discussion.

EGFR MUTATIONS

CASE PRESENTATION 1

A 54-year-old Caucasian man who is a former smoker with a 10 pack-year history and past medical history of hypertension and dyslipidemia presents with progressive dyspnea for several weeks. A chest x-ray shows moderate pleural effusion on the left side with possible mass-like opacity on the left upper lung field. An ultrasound-guided thoracentesis is performed and cytology is positive for adenocarcinoma of likely pulmonary origin. Staging workup including positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging of the brain with and without contrast is done. PET/CT shows a 5.5-cm mass in the left upper lobe of the lung with high fluorodeoxyglucose (FDG) uptake, several 1- to 2-cm mediastinal lymph nodes with moderate FDG uptake, and small pleural effusion on both sides with moderate FDG uptake. MRI-brain is negative for malignancy. The patient subsequently undergoes a CT-guided biopsy of the lung mass, which shows moderately differentiated adenocarcinoma. Comprehensive molecular profiling reveals EGFR L858R mutation only. The patient now presents for the initial consultation. Of note, his Eastern Cooperative Oncology Group performance status is 1.

• What is the next step in the management of this patient?

FIRST-LINE TKI FOR SENSITIZING EGFR MUTATIONS

The 2 most common EGFR mutations are deletions in exon 19 and substitution of arginine for leucine in exon 21 (L858R), found in approximately 45% and 40% of patients with EGFR mutations, respectively.³⁶ Both mutations are sensitive to EGFR TKIs. The benefit may be greater in patients with exon 19 deletions as compared to exon 21 L858R substitution,^37,38 but this has not been demonstrated consistently in clinical trials.^39-43 In the United States, EGFR mutations are found in approximately 10% of patients with NSCLC, while the incidence can be as high as 50% in Asia.⁴⁴ Even though the cobas EGFR mutation test is the companion diagnostic approved by the US FDA, a positive test result from any laboratory with the Clinical Laboratory Improvement Amendments (CLIA) certificate should prompt the use of an EGFR TKI as the initial treatment.

Three EGFR TKIs that have been approved as first-line therapy in the United States are available: erlotinib, afatinib, and gefitinib.⁵ Both erlotinib and gefitinib are considered first-generation TKIs. They have higher binding affinity for the 2 common EGFR mutations than wild-type EGFR. In addition, they reversibly bind to the intracellular tyrosine kinase domain, resulting in inhibition of autophosphorylation of the tyrosine residues. Afatinib, a second-generation and irreversible TKI, targets EGFR (HER1) as well as HER2 and HER4.⁴⁵

The superior efficacy of the EGFR TKIs over platinum doublet chemotherapy in treatment-naïve patients with EGFR mutations has been demonstrated in 7 randomized trials to date (Table).⁴⁶ Erlotinib was the TKI arm for the OPTIMAL,⁴¹ EURTAC,⁴² and ENSURE trials;³⁸ afatinib was the TKI arm for LUX-LUNG 3³⁷ and 6;⁴³ gefitinib was the TKI arm for NEJ002^39,47 and WJTOG3405.⁴⁰ A meta-analysis of these 7 trials by Lee et al showed that progression-free survival (PFS) was significantly prolonged by EGFR TKIs (hazard ratio [HR] 0.37 [95% confidence interval {CI} 0.32 to 0.42]).⁴⁶ For instance, in the EURTAC trial, median PFS was 9.7 months for patients treated with erlotinib as compared to 5.2 months for patients treated with platinum/gemcitabine or platinum/docetaxel.⁴² In this meta-analysis, prespecified subgroups included age, sex, ethnicity, smoking status, performance status, tumor histology, and EGFR mutation subtype. The superior outcome with TKIs was observed in all subgroups. Furthermore, patients with exon 19 deletions, nonsmokers, and women had even better outcomes.⁴⁶

Erlotinib is the most commonly used TKI in the United States largely because gefitinib was off the market for some time until it was re-approved by the FDA in 2015. Interestingly, this “re-approval” was not based on either 1 of the 2 prospective trials (NEJ002^39,47 and WJTOG3405⁴⁰), but rather was based on an exploratory analysis of the IPASS trial^48,49 as well as a prospective phase 4, single-arm trial in Europe (IFUM).⁵⁰ The superior efficacy of gefitinib over carboplatin/paclitaxel among patients with EGFR mutations in the IPASS trial was confirmed by blind independent central review, with longer PFS (HR 0.54 [95% CI 0.38 to 0.79] P = 0.0012) and higher objective response rate (ORR; odds ratio 3 [95% CI 1.63 to 5.54], P = 0.0004).⁴⁹

CASE 1 CONTINUED

Based on the EGFR L858R mutation status, the patient is started on erlotinib. He is quite happy that he does not need intravenous chemotherapy but wants to know what toxicities he might potentially have with erlotinib.

• What are the common adverse effects (AEs) of EGFR TKIs? How are AEs of TKIs managed?

Safety Profile

The important toxicities associated with EGFR TKIs are rash, gastrointestinal toxicity, hepatic toxicity, and pulmonary toxicity. Rash is an AE specific to all agents blocking the EGFR pathway, including small molecules and monoclonal antibodies such as cetuximab. The epidermis has a high level of expression of EGFR, which contributes to this toxicity.⁵¹ Rash usually presents as dry skin or acneiform eruption. Prophylactic treatment with oral tetracyclines and topical corticosteroids is generally recommended upon initiation of TKI therapy. Diarrhea is the most prevalent gastrointestinal toxicity. All patients starting treatment should be given prescriptions to manage diarrhea such as loperamide and be advised to call when it occurs. Hepatic toxicity is often manifested as elevated transaminases or bilirubin. Interstitial lung disease (ILD) is a rare but potentially fatal pulmonary toxicity.

Rash of any grade was reported in 49.2% of patients treated with erlotinib in clinical trials, while grade 3 rash occurred in 6% of patients and no grade 4 was reported. Diarrhea of any grade was reported in 20.3% of patients, grade 3 diarrhea occurred in 1.8%, and no grade 4 was reported. Grade 2 and 3 alanine aminotransferase (ALT) elevations were seen in 2% and 1% of patients, respectively. Grade 2 and 3 bilirubin elevations were seen in 4% and less than 1% of patients, respectively. The incidence of serious ILD-like events was less than 1%.⁵²

Afatinib is associated with higher incidences of rash and diarrhea. Specifically, diarrhea and rash of all grades were reported in 96% and 90% of patients treated with afatinib, respectively. Paronychia of all grades occurred in 58% of patients. Elevated ALT of all grades was seen in 11% of patients. Approximately 1.5% of patients treated with afatinib across clinical trials had ILD or ILD-like AEs.⁵³

Gefitinib, the most commonly used TKI outside United States, has a toxicity profile similar to erlotinib, except for hepatic toxicity. For instance, rash of all grades occurred in 47% of patients, diarrhea of all grades occurred in 29% of patients, and ILD or ILD-like AEs occurred in 1.3% of patients across clinical trials. In comparison, elevated ALT and aspartate aminotransferase (AST) of all grades was seen in 38% and 40% of patients, respectively.⁵⁴ Therefore, close monitoring of liver function is clinically warranted. In particular, patients need to be advised to avoid concomitant use of herbal supplements, a common practice in Asian countries.

CASE 1 CONTINUED

The patient does well while on erlotinib at 150 mg orally once daily for about 8 months, until he develops increasing abdominal pain. A CT scan of the abdomen and pelvis with contrast shows a new 8-cm right adrenal mass. Additionally, a repeat CT scan of the chest with contrast shows a stable lung mass but enlarging mediastinal lymphadenopathy.

• How would you manage the patient at this point?

MANAGEMENT OF T790M MUTATION AFTER PROGRESSION ON FIRST-LINE EGFR TKIS

As mentioned above, the median PFS of patients with EGFR mutations treated with 1 of the 3 TKIs is around 9 to 13 months.⁴⁶ Of the various resistance mechanisms that have been described, the T790M mutation is found in approximately 60% of patients who progress after treatment with first-line TKIs.^55,56 Other mechanisms, such as HER2 amplification, MET amplification, or rarely small cell transformation, have been reported.⁵⁶ The first- and second-generation EGFR TKIs function by binding to the ATP-binding domain of mutated EGFR, leading to inhibition of the downstream signaling pathways (Figure, part B) and ultimately cell death.³⁵ The T790M mutation hinders the interaction between the ATP-binding domain of EGFR kinase and TKIs, resulting in treatment resistance and disease progression.^57,58

Osimertinib is a third-generation irreversible EGFR TKI with activity against both sensitizing EGFR and resistant T790M mutations. It has low affinity for wide-type EGFR as well as insulin receptor and insulin-like growth factor receptor.⁵⁹ Osimertinib has been fully approved for NSCLC patients with EGFR mutations who have progressed on first-line EGFR TKIs with the development of T790M mutation. An international phase 3 trial (AURA3) randomly assigned 419 patients in a 2:1 ratio to either osimertinib or platinum/pemetrexed. Eligible patients all had the documented EGFR mutations and disease progression after first-line EGFR TKIs. Central confirmation of the T790M mutation was required. Median PFS by investigator assessment, the trial’s primary end point, was 10.1 months for osimertinib versus 4.4 months for chemotherapy (HR 0.3 [95% CI 0.23 to 0.41]; P < 0.001). ORR was 71% for osimertinib versus 31% for chemotherapy (HR 5.39 [95% CI 3.47 to 8.48], P < 0.001). A total of 144 patients with stable and asymptomatic brain metastases were also eligible. Median PFS for this subset of patients treated with osimertinib and chemotherapy was 8.5 months and 4.2 months, respectively (HR 0.32 [95% CI 0.21 to 0.49]). In the AURA3 trial, osimertinib was better tolerated than chemotherapy, with 23% of patients treated with osimertinib experiencing grade 3 or 4 AEs as compared to 47% of chemotherapy-treated patients. The most common AEs of any grade were diarrhea (41%), rash (34%), dry skin (23%), and paronychia (22%).⁶⁰

For the case patient, a reasonable approach would be to obtain a tissue biopsy of the adrenal mass and more importantly to check for the T790M mutation. Similar to the companion diagnostic for EGFR mutations, the cobas EGFR mutation test v2 is the FDA-approved test for T790M. However, if this resistance mutation is detected by any CLIA-certified laboratories, osimertinib should be the recommended treatment option. If tissue biopsy is not feasible, plasma-based testing should be considered. A blood-based companion diagnostic also is FDA approved.

ALK REARRANGEMENTS

CASE 2 PRESENTATION

A 42-year-old Korean woman who is a non-smoker with no significant past medical history presents with fatigue, unintentional weight loss of 20 lb in the past 4 months, and vague abdominal pain. A CT can of the abdomen and pelvis without contrast shows multiple foci in the liver and an indeterminate nodule in the right lung base. She subsequently undergoes PET/CT, which confirms multiple liver nodules/masses ranging from 1 to 3 cm with moderate FDG uptake. In addition, there is a 3.5-cm pleura-based lung mass on the right side with moderate FDG uptake. MRI-brain with and without contrast is negative for malignancy. A CT-guided biopsy of 1 of the liver masses is ordered and pathology returns positive for poorly differentiated adenocarcinoma consistent with lung primary. Molecular analysis reveals an echinoderm microtubule-associated protein-like 4 (EML4)-ALK rearrangement. She is placed on crizotinib by an outside oncologist and after about 3 weeks of therapy is doing well. She is now in your clinic for a second opinion. She says that some of her friends told her about another medication called ceritinib and was wondering if she would need to switch her cancer treatment.

• How would you respond to this patient’s inquiry?

FIRST-LINE TKIS FOR ALK REARRANGEMENTS

ALK rearrangements are found in 2% to 7% of NSCLC, with EML4-ALK being the most prevalent fusion variant.⁶¹ The inversion of chromosome 2p leads to the fusion of the EML4 gene and the ALK gene, which causes the constitutive activation of the fusion protein and ultimately increased transformation and tumorigenicity.^7,61 Patients harboring ALK rearrangements tend to be non-smokers. Adenocarcinoma, especially signet ring cell subtype, is the predominant histology. Compared to EGFR mutations, patients with ALK mutations are significantly younger and more likely to be men.⁶²ALK rearrangements can be detected by either FISH or IHC, and most next-generation sequencing (NGS) panels have the ability to identify this driver mutation.

Crizotinib is the first approved ALK inhibitor for the treatment of NSCLC in this molecular subset of patients.⁶³ PROFILE 1014 is a phase 3 randomized trial that compared crizotinib with chemotherapy containing platinum/pemetrexed for up to 6 cycles. Crossover to crizotinib was allowed for patients with disease progression on chemotherapy. The primary end point was PFS by independent radiologic review. The crizotinib arm demonstrated superior PFS (10.9 months versus 7 months; HR 0.45 [95% CI 0.35 to 0.6], P < 0.001) and ORR (74% versus 45%, P < 0.001). Median survival was not reached in either arm (HR 0.82 [95% CI 0.54 to 1.26], P = 0.36).⁶⁴ Based on this international trial, crizotinib is considered standard of care in the United States for treatment-naïve patients with advanced NSCLC harboring ALK rearrangements. The current recommended dose is 250 mg orally twice daily. Common treatment-related AEs of all grades include vision disorder (62%), nausea (53%), diarrhea (43%), vomiting (40%), edema (28%), and constipation (27%).⁶⁵ PROFILE 1007 compared crizotinib with pemetrexed or docetaxel in ALK-rearranged NSCLC patients with prior exposure to 1 platinum-based chemotherapy. The median PFS was 7.7 months for crizotinib as compared to 3 months for chemotherapy (HR 0.49 [95% CI 0.37 to 0.64], P < 0.001). The response rates were 65% and 20% for crizotinib and chemotherapy, respectively (P < 0.001).⁶⁶ In other countries, crizotinib following 1 prior platinum-based regimen may be considered standard of care based on this trial.

Ceritinib is an oral second-generation ALK inhibitor that is 20 times more potent than crizotinib based on enzymatic assays.⁶⁷ It also targets ROS1 and insulin-like growth factor 1 receptor but not c-MET. It was first approved by the FDA in April 2014 for metastatic ALK-rearranged NSCLC following crizotinib.⁶⁸ In May 2017, the FDA granted approval of ceritinib for treatment-naïve patients. This decision was based on the results of the ASCEND-4 trial, a randomized phase 3 trial assessing the efficacy and safety of ceritinib over chemotherapy in the first-line setting. The trial assigned 376 patients to either ceritinib at 750 mg once daily or platinum/pemetrexed for 4 cycles followed by maintenance pemetrexed. Median PFS was 16.6 months for ceritinib versus 8.1 months for chemotherapy (HR 0.55 [95% CI 0.42 to 0.73]; P < 0.00001).⁶⁹ Toxicities of ceritinib are not negligible, with gastrointestinal toxicity being the most prevalent. For instance, diarrhea, nausea, vomiting, abdominal pain, and constipation of all grades were seen in 86%, 80%, 60%, 54%, and 29% of patients, respectively. Furthermore, fatigue and decreased appetite occurred in 52% and 34% of patients, respectively. In terms of laboratory abnormalities, 84% of patients experienced decreased hemoglobin of all grades; 80% increased ALT; 75% increased AST; 58% increased creatinine; 49% increased glucose; 36% decreased phosphate; and 28% increased lipase. Due to these AEs, the incidence of dose reduction was about 58% and the median onset was around 7 weeks.⁷⁰

Alectinib is another oral second-generation ALK inhibitor that was approved by the FDA in December 2015 for the treatment of NSCLC patients with ALK rearrangements who have progressed on or are intolerant to crizotinib.⁷¹ Its indication will soon be broadened to the first-line setting based on the ALEX trial.⁷² Alectinib is a potent and highly selective TKI of ALK⁷³ with activity against known resistant mutations to crizotinib.^74,75 It also inhibits RET but not ROS1 or c-MET.⁷⁶ ALEX, a randomized phase 3 study, compared alectinib with crizotinib in treatment-naïve patients with NSCLC harboring ALK rearrangements. The trial enrolled 303 patients and the median follow-up was approximately 18 months. The alectinib arm (600 mg twice daily) demonstrated significantly higher PFS by investigator-assessment, the trial’s primary end point. The 12-month event-free survival was 68.4% (95% CI 61% to 75.9%) versus 48.7% (95% CI 40.4% to 56.9%) for alectinib and crizotinib, respectively (HR 0.47 [95% CI 0.34 to 0.65], P < 0.001). The median PFS was not reached in the alectinib arm (95% CI 17.7 months to not estimable) as compared to 11.1 months in the crizotinib arm (95% CI 9.1 to 13.1 months).⁷² Alectinib is generally well tolerated. Common AEs of all grades include fatigue (41%), constipation (34%), edema (30%), and myalgia (29%). As alectinib can cause anemia, lymphopenia, hepatic toxicity, increased creatine phosphokinase, hyperglycemia, electrolyte abnormalities, and increased creatinine, periodic monitoring of these laboratory values is important, although most of these abnormalities are grade 1 or 2.⁷⁷

Brigatinib, another oral second-generation ALK inhibitor, was granted accelerated approval by the FDA in April 2017 for ALK-rearranged and crizotinib-resistant NSCLC based on the ALTA trial. This randomized phase 2 study of brigatinib showed an ORR by investigator assessment of 54% (97.5% CI 43% to 65%) in the 180 mg once daily arm with lead-in of 90 mg once daily for 7 days. Median PFS was 12.9 months (95% CI 11.1 months to not reached [NR]).⁷⁸ Currently, a phase 3 study of brigatinib versus crizotinib in ALK inhibitor–naïve patients is recruiting participants (ALTA-1L). It will be interesting to see if brigatinib can achieve a front-line indication.

Starting the case patient on crizotinib is well within the treatment guidelines. One may consider ceritinib or alectinib in the first-line setting, but both TKIs can be reserved upon disease progression. We would recommend a repeat biopsy at that point to look for resistant mechanisms, as certain secondary ALK mutations may be rescued by certain next-generation ALK inhibitors. For instance, the F1174V mutation has been reported to confer resistance to ceritinib but sensitivity to alectinib, while the opposite is true for I1171T. The G1202R mutation is resistant to ceritinib, alectinib, and brigatinib, but lorlatinib, a third-generation ALK inhibitor, has shown activity against this mutation.⁷⁹ Furthermore, brain metastasis represents a treatment challenge for patients with ALK rearrangements. It is also an efficacy measure of next-generation ALK inhibitors, all of which have demonstrated better central nervous system activity than crizotinib.^69,78,80 If the case patient were found to have brain metastasis at the initial diagnosis, either ceritinib or alectinib would be a reasonable choice since crizotinib has limited penetration of blood-brain barrier.⁸¹

ROS1 REARRANGEMENTS

CASE PRESENTATION 3

A 66-year-old Chinese woman who is a non-smoker with a past medical history of hypertension and hypothyroidism presents to the emergency department for worsening lower back pain. Initial workup includes x-ray of the lumbar spine followed by MRI with contrast, which shows a soft tissue mass at L3-4 without cord compression. CT of the chest, abdomen, and pelvis with contrast shows a 7-cm right hilar mass, bilateral small lung nodules, mediastinal lymphadenopathy, and multiple lytic lesions in ribs, lumbar spine, and pelvis. MRI-brain with and without contrast is negative for malignancy. She undergoes endo-bronchial ultrasound and biopsy of the right hilar mass, which shows poorly differentiated adenocarcinoma. While waiting for the result of the molecular analysis, the patient undergoes palliative radiation therapy to L2-5 with good pain relief. She is discharged from the hospital and presents to your clinic for follow up. Molecular analysis now reveals ROS1 rearrangement with CD74-ROS1 fusion.

• What treatment plan should be put in place for this patient?

FIRST-LINE THERAPY FOR ROS1 REARRANGEMENTS

Approximately 2.4% of lung adenocarcinomas harbor ROS1 rearrangements.⁸² This distinct genetic alteration occurs more frequently in NSCLC patients who are younger, female, and never-smokers, and who have adenocarcinomas.⁸ It has been shown that ROS1 rearrangements rarely overlap with other genetic alterations including KRAS mutations, EGFR mutations, and ALK rearrangements.⁸³ As a receptor tyrosine kinase, ROS1 is similar to ALK and insulin receptor family members.⁸⁴ Crizotinib, which targets ALK, ROS1, and c-MET, was approved by the FDA on March 11, 2016, for the treatment of metastatic ROS1-rearranged NSCLC.⁸⁵ The approval was based on a phase 2 expansion cohort of the original phase 1 study. Among 50 US patients enrolled in this expansion cohort, 3 had complete responses and 33 had partial responses with ORR of 72% (95% CI 58% to 84%). Median PFS was 19.2 months (95% CI 14.4 months to NR) and median duration of response (DOR) was 17.6 months (95% CI 14.5 months to NR).⁸⁶ During longer follow-up, independent radiology review confirmed high ORR of 66% and median DOR of 18.3 months.⁸⁵

Interestingly, no companion diagnostic assay has been approved for the detection of ROS1 rearrangements with the approval of crizotinib. In the United States, break apart FISH is the most common detection method. In fact, in the above mentioned phase 2 study, ROS1 rearrangements were detected in 49 out of 50 patients by this method.⁸⁶ FISH can be technically challenging when dealing with high volume and multiple targets. Reverse transcriptase-PCR is another detection method, but it requires knowledge of the fusion partners. To date, at least 14 ROS1 fusion partners have been reported, with CD74 being the most common.⁸⁷ NGS with appropriate design and validation can also be used to detect ROS1 rearrangements.

For the case patient, the recommendation would be to start her on crizotinib at 250 mg twice daily. Monitoring for vision disturbance, gastrointestinal complaints, and edema is warranted. Because the estimated onset of response is around 7.9 weeks,⁸⁶ plans should be made to repeat her scans in approximately 2 months.

BRAF V600E MUTATIONS

CASE PRESENTATION 4

A 71-year-old Caucasian man with a past medical history of hypertension, dyslipidemia, and ischemic cerebrovascular accident without residual deficits was diagnosed with stage IV adenocarcinoma of the lung about 8 months ago. He has a 40 pack-year smoking history and quit smoking when he was diagnosed with lung cancer. His disease burden involved a large mediastinal mass, scattered pleural nodules, multiple lymphadenopathy, and several soft tissue masses. His outside oncologist started him on chemotherapy containing carboplatin and pemetrexed for 6 cycles followed by maintenance pemetrexed. The most recent restaging scans show disease progression with enlarging soft tissue masses and several new lytic bone lesions. MRI-brain with and without contrast shows 2 subcentimeter enhancing lesions. He transferred care to you approximately 4 weeks ago. You ordered a repeat biopsy of 1 of the enlarging soft tissue masses. Molecular analysis revealed BRAF V600E mutation. In the interim, he underwent stereotactic radiosurgery for the 2 brain lesions without any complications. The patient is now in your clinic for follow up.

• What would be your recommended systemic treatment?

TARGETED THERAPIES FOR BRAF V600E MUTATION

BRAF mutations were first recognized as activating mutations in advanced melanomas, with BRAF V600E, resulting from the substitution of glutamic acid for valine at amino acid 600, being the most common. BRAF plays an important role in the mitogen-activated protein kinase (MAPK) signaling pathway. Briefly, the activation of MAPK pathway occurs upon ligand binding of receptor tyrosine kinases, which then involves RAS/BRAF/MEK/ERK in a stepwise manner, ultimately leading to cell survival. BRAF mutations have been increasingly recognized also as driver mutations in NSCLC.^9–12 They can be detected by PCR or NGS method. The characteristics of NSCLC patients harboring BRAF mutations have been described by various groups.^9–12 For instance, 1 case series showed that the incidence was 2.2% among patients with advanced lung adenocarcinoma; 50% of mutations were V600E, while G469A and D594G accounted for the remaining 39% and 11% of patients, respectively. All patients were either current or former smokers. The median OS of patients with BRAF mutations in this case series was NR, while it was 37 months for patients with EGFR mutations (P = 0.73) and NR for patients with ALK rearrangements (P = 0.64).⁹

For patients with BRAF V600E–mutant NSCLC who have progressed on platinum-based chemotherapy, the combination of dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor) may represent a new treatment paradigm. This was illustrated in a phase 2, nonrandomized, open-label study. A total of 57 patients were enrolled and 36 patients (63.2% [95% CI 49.3% to 75.6%]) achieved an overall response by investigator assessment, the trial’s primary end point. Disease control rate was 78.9% (95% CI 66.1% to 88.6%), with 4% complete response, 60% partial response, and 16% stable disease. PFS was 9.7 months (95% CI [6.9 to 19.6 months]). The safety profile was comparable to what had been observed in patients with melanoma treated with this regimen. More specifically, 56% of patients on this trial reported serious AEs, including pyrexia (16%), anemia (5%), confusional state (4%), decreased appetite (4%), hemoptysis (4%), hypercalcemia (4%), nausea (4%), and cutaneous squamous cell carcinoma (4%). In addition, neutropenia (9%) and hyponatremia (7%) were the most common grade 3-4 AEs.¹⁶

The case patient has experienced disease progression after 1 line of platinum-based chemotherapy, so the combination of dabrafenib and trametinib would be a robust systemic treatment option. dabrafenib as a single agent has also been studied in BRAF V600E–mutant NSCLC in a phase 2 trial. The overall response by investigator assessment among 84 patients was 33% (95% CI 23% to 45%).¹⁴ Vemurafenib, another oral BRAF TKI, has demonstrated efficacy for NSCLC patients harboring BRAF V600E mutation. In the cohort of 20 patients with NSCLC, the response rate was 42% (95% CI 20% to 67%) and median PFS was 7.3 months (95% CI 3.5 to 10.8 months).¹³ Patients with non-V600E mutations have shown variable responses to targeted therapies. MEK TKIs may be considered in this setting; however, the details of this discussion are beyond the scope of this review.

CONCLUSION

The management of advanced NSCLC with driver mutations has seen revolutionary changes over the past decade. Tremendous research has been done in order to first understand the molecular pathogenesis of NSCLC and then discover driver mutations that would lead to development of targeted therapies with clinically significant efficacy as well as tolerability. More recently, increasing efforts have focused on how to conquer acquired resistance in patients with disease progression after first-line TKIs. The field of EGFR-mutant NSCLC has set a successful example, but the work is nowhere near finished. The goals are to search for more driver mutations and to design agents that could potentially block cell survival signals once and for all.

INTRODUCTION

Lung cancer is the second most common type of cancer in the United States, with 222,500 estimated new cases in 2017, according to the American Cancer Society.¹ However, it is by far the number one cause of death due to cancer, with an estimated 155,870 lung cancer–related deaths occurring in 2017, which is higher than the number of deaths due to breast cancer, prostate cancer, and colorectal cancer combined.^1,2 Despite slightly decreasing incidence and mortality over the past decade, largely due to smoking cessation, the 5-year survival rate of lung cancer remains dismal at approximately 18%.^2–4

Non-small cell lung cancer (NSCLC) accounts for 80% to 85% of all lung cancer cases.⁴ Traditionally, it is further divided based on histology: adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and not otherwise specified.⁵ Chemotherapy had been the cornerstone of treatment for stage IV NSCLC. It is not target-specific and is most effective against rapidly growing cells. Common adverse effects include alopecia, nausea/vomiting, myelosuppression, cardiotoxicity, neuropathy, and nephrotoxicity. However, this paradigm has shifted following the discovery of mutations of the epidermal growth factor receptor (EGFR) gene as an oncogenic driver that confers sensitivity to small molecule tyrosine kinase inhibitors (TKIs) targeting EGFR.⁶ The EGFR inhibitors are given orally and have a spectrum of toxicities (eg, such as rash, diarrhea, and elevated transaminases) different from that of systemic chemotherapy, which is often administered intravenously. Following the discovery of EGFR mutations, rearrangements of the anaplastic lymphoma kinase (ALK) gene⁷ and ROS1 gene⁸ were identified as targetable driver mutations in NSCLC. The frequency of both rearrangements is lower than that of EGFR mutations. Additionally, BRAF V600E mutation has been identified in NSCLC.^9–12 This activation mutation is commonly seen in melanoma. Agents that have already been approved for the treatment of melanoma with the BRAF V600E mutation are being tested in NSCLC patients with this mutation.^13–16

Given the effectiveness and tolerability of targeted therapy, identifying this distinct molecular subset of NSCLC patients is critical in treatment. Currently, molecular testing is mandatory in all stage IV patients with non-squamous cell carcinoma, as a preponderance of patients with driver mutations have this histology subtype.^5,17–19 For patients with squamous cell carcinoma, molecular testing should be considered if the biopsy specimen is small, there is mixed histology, or the patient is a nonsmoker.^5,20 Several techniques are commonly utilized in detecting these genetic alterations. EGFR mutation can be detected by polymerase chain reaction (PCR), ALK or ROS1 rearrangement can be detected by fluorescence in-situ hybridization (FISH), and immunohistochemistry (IHC) can also be used to detect ALK rearrangement. The current guideline is to use comprehensive genomic profiling to capture all the potential molecular targets simultaneously instead of running stepwise tests just for EGFR, ALK, and ROS1.⁵BRAF V600E mutation,^13–16 MET exon 14 skipping mutation,^21–24 RET rearrangements,^25–27 and HER2 mutations^28–30 are among the emergent genetic alterations with various responses to targeted therapy.³¹ Some of these targeted agents have been approved for other types of malignancy, and others are still in the development phase.

Several initiatives worldwide have reported better outcomes of patients with driver mutations treated with targeted therapy. For instance, the Lung Cancer Mutation Consortium in the United States demonstrated that the median survival of patients without driver mutations, with drivers mutations but not treated with targeted therapy, and with driver mutations and treated with targeted therapy was 2.08 years, 2.38 years, and 3.49 years, respectively.³² The French Cooperative Thoracic Intergroup-French National Cancer Institute demonstrated that the median survival for patients with driver mutations versus those without driver mutations was 16.5 months versus 11.8 months.³³ The Spanish Lung Cancer Group demonstrated that the overall survival (OS) for patients with EGFR mutations treated with erlotinib was 27 months.³⁴ The mutations in lung cancer, their frequencies, and the downstream signaling pathways are depicted in the Figure.³⁵

In this article, we discuss targeted therapy for patients with EGFR mutations, ALK rearrangements, ROS1 rearrangements, and BRAF V600E mutation. We also discuss the management of patients with EGFR mutations who develop a secondary mutation after TKI therapy. Almost all of the targeted agents discussed herein have been approved by the US Food and Drug Administration (FDA), so they are considered standard of care. All available phase 3 trials pertinent to these targeted therapies are included in the discussion.

EGFR MUTATIONS

CASE PRESENTATION 1

A 54-year-old Caucasian man who is a former smoker with a 10 pack-year history and past medical history of hypertension and dyslipidemia presents with progressive dyspnea for several weeks. A chest x-ray shows moderate pleural effusion on the left side with possible mass-like opacity on the left upper lung field. An ultrasound-guided thoracentesis is performed and cytology is positive for adenocarcinoma of likely pulmonary origin. Staging workup including positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging of the brain with and without contrast is done. PET/CT shows a 5.5-cm mass in the left upper lobe of the lung with high fluorodeoxyglucose (FDG) uptake, several 1- to 2-cm mediastinal lymph nodes with moderate FDG uptake, and small pleural effusion on both sides with moderate FDG uptake. MRI-brain is negative for malignancy. The patient subsequently undergoes a CT-guided biopsy of the lung mass, which shows moderately differentiated adenocarcinoma. Comprehensive molecular profiling reveals EGFR L858R mutation only. The patient now presents for the initial consultation. Of note, his Eastern Cooperative Oncology Group performance status is 1.

• What is the next step in the management of this patient?

FIRST-LINE TKI FOR SENSITIZING EGFR MUTATIONS

The 2 most common EGFR mutations are deletions in exon 19 and substitution of arginine for leucine in exon 21 (L858R), found in approximately 45% and 40% of patients with EGFR mutations, respectively.³⁶ Both mutations are sensitive to EGFR TKIs. The benefit may be greater in patients with exon 19 deletions as compared to exon 21 L858R substitution,^37,38 but this has not been demonstrated consistently in clinical trials.^39-43 In the United States, EGFR mutations are found in approximately 10% of patients with NSCLC, while the incidence can be as high as 50% in Asia.⁴⁴ Even though the cobas EGFR mutation test is the companion diagnostic approved by the US FDA, a positive test result from any laboratory with the Clinical Laboratory Improvement Amendments (CLIA) certificate should prompt the use of an EGFR TKI as the initial treatment.

Three EGFR TKIs that have been approved as first-line therapy in the United States are available: erlotinib, afatinib, and gefitinib.⁵ Both erlotinib and gefitinib are considered first-generation TKIs. They have higher binding affinity for the 2 common EGFR mutations than wild-type EGFR. In addition, they reversibly bind to the intracellular tyrosine kinase domain, resulting in inhibition of autophosphorylation of the tyrosine residues. Afatinib, a second-generation and irreversible TKI, targets EGFR (HER1) as well as HER2 and HER4.⁴⁵

The superior efficacy of the EGFR TKIs over platinum doublet chemotherapy in treatment-naïve patients with EGFR mutations has been demonstrated in 7 randomized trials to date (Table).⁴⁶ Erlotinib was the TKI arm for the OPTIMAL,⁴¹ EURTAC,⁴² and ENSURE trials;³⁸ afatinib was the TKI arm for LUX-LUNG 3³⁷ and 6;⁴³ gefitinib was the TKI arm for NEJ002^39,47 and WJTOG3405.⁴⁰ A meta-analysis of these 7 trials by Lee et al showed that progression-free survival (PFS) was significantly prolonged by EGFR TKIs (hazard ratio [HR] 0.37 [95% confidence interval {CI} 0.32 to 0.42]).⁴⁶ For instance, in the EURTAC trial, median PFS was 9.7 months for patients treated with erlotinib as compared to 5.2 months for patients treated with platinum/gemcitabine or platinum/docetaxel.⁴² In this meta-analysis, prespecified subgroups included age, sex, ethnicity, smoking status, performance status, tumor histology, and EGFR mutation subtype. The superior outcome with TKIs was observed in all subgroups. Furthermore, patients with exon 19 deletions, nonsmokers, and women had even better outcomes.⁴⁶

Erlotinib is the most commonly used TKI in the United States largely because gefitinib was off the market for some time until it was re-approved by the FDA in 2015. Interestingly, this “re-approval” was not based on either 1 of the 2 prospective trials (NEJ002^39,47 and WJTOG3405⁴⁰), but rather was based on an exploratory analysis of the IPASS trial^48,49 as well as a prospective phase 4, single-arm trial in Europe (IFUM).⁵⁰ The superior efficacy of gefitinib over carboplatin/paclitaxel among patients with EGFR mutations in the IPASS trial was confirmed by blind independent central review, with longer PFS (HR 0.54 [95% CI 0.38 to 0.79] P = 0.0012) and higher objective response rate (ORR; odds ratio 3 [95% CI 1.63 to 5.54], P = 0.0004).⁴⁹

CASE 1 CONTINUED

Based on the EGFR L858R mutation status, the patient is started on erlotinib. He is quite happy that he does not need intravenous chemotherapy but wants to know what toxicities he might potentially have with erlotinib.

• What are the common adverse effects (AEs) of EGFR TKIs? How are AEs of TKIs managed?

Safety Profile

The important toxicities associated with EGFR TKIs are rash, gastrointestinal toxicity, hepatic toxicity, and pulmonary toxicity. Rash is an AE specific to all agents blocking the EGFR pathway, including small molecules and monoclonal antibodies such as cetuximab. The epidermis has a high level of expression of EGFR, which contributes to this toxicity.⁵¹ Rash usually presents as dry skin or acneiform eruption. Prophylactic treatment with oral tetracyclines and topical corticosteroids is generally recommended upon initiation of TKI therapy. Diarrhea is the most prevalent gastrointestinal toxicity. All patients starting treatment should be given prescriptions to manage diarrhea such as loperamide and be advised to call when it occurs. Hepatic toxicity is often manifested as elevated transaminases or bilirubin. Interstitial lung disease (ILD) is a rare but potentially fatal pulmonary toxicity.

Rash of any grade was reported in 49.2% of patients treated with erlotinib in clinical trials, while grade 3 rash occurred in 6% of patients and no grade 4 was reported. Diarrhea of any grade was reported in 20.3% of patients, grade 3 diarrhea occurred in 1.8%, and no grade 4 was reported. Grade 2 and 3 alanine aminotransferase (ALT) elevations were seen in 2% and 1% of patients, respectively. Grade 2 and 3 bilirubin elevations were seen in 4% and less than 1% of patients, respectively. The incidence of serious ILD-like events was less than 1%.⁵²

Afatinib is associated with higher incidences of rash and diarrhea. Specifically, diarrhea and rash of all grades were reported in 96% and 90% of patients treated with afatinib, respectively. Paronychia of all grades occurred in 58% of patients. Elevated ALT of all grades was seen in 11% of patients. Approximately 1.5% of patients treated with afatinib across clinical trials had ILD or ILD-like AEs.⁵³

Gefitinib, the most commonly used TKI outside United States, has a toxicity profile similar to erlotinib, except for hepatic toxicity. For instance, rash of all grades occurred in 47% of patients, diarrhea of all grades occurred in 29% of patients, and ILD or ILD-like AEs occurred in 1.3% of patients across clinical trials. In comparison, elevated ALT and aspartate aminotransferase (AST) of all grades was seen in 38% and 40% of patients, respectively.⁵⁴ Therefore, close monitoring of liver function is clinically warranted. In particular, patients need to be advised to avoid concomitant use of herbal supplements, a common practice in Asian countries.

CASE 1 CONTINUED

The patient does well while on erlotinib at 150 mg orally once daily for about 8 months, until he develops increasing abdominal pain. A CT scan of the abdomen and pelvis with contrast shows a new 8-cm right adrenal mass. Additionally, a repeat CT scan of the chest with contrast shows a stable lung mass but enlarging mediastinal lymphadenopathy.

• How would you manage the patient at this point?

MANAGEMENT OF T790M MUTATION AFTER PROGRESSION ON FIRST-LINE EGFR TKIS

As mentioned above, the median PFS of patients with EGFR mutations treated with 1 of the 3 TKIs is around 9 to 13 months.⁴⁶ Of the various resistance mechanisms that have been described, the T790M mutation is found in approximately 60% of patients who progress after treatment with first-line TKIs.^55,56 Other mechanisms, such as HER2 amplification, MET amplification, or rarely small cell transformation, have been reported.⁵⁶ The first- and second-generation EGFR TKIs function by binding to the ATP-binding domain of mutated EGFR, leading to inhibition of the downstream signaling pathways (Figure, part B) and ultimately cell death.³⁵ The T790M mutation hinders the interaction between the ATP-binding domain of EGFR kinase and TKIs, resulting in treatment resistance and disease progression.^57,58

Osimertinib is a third-generation irreversible EGFR TKI with activity against both sensitizing EGFR and resistant T790M mutations. It has low affinity for wide-type EGFR as well as insulin receptor and insulin-like growth factor receptor.⁵⁹ Osimertinib has been fully approved for NSCLC patients with EGFR mutations who have progressed on first-line EGFR TKIs with the development of T790M mutation. An international phase 3 trial (AURA3) randomly assigned 419 patients in a 2:1 ratio to either osimertinib or platinum/pemetrexed. Eligible patients all had the documented EGFR mutations and disease progression after first-line EGFR TKIs. Central confirmation of the T790M mutation was required. Median PFS by investigator assessment, the trial’s primary end point, was 10.1 months for osimertinib versus 4.4 months for chemotherapy (HR 0.3 [95% CI 0.23 to 0.41]; P < 0.001). ORR was 71% for osimertinib versus 31% for chemotherapy (HR 5.39 [95% CI 3.47 to 8.48], P < 0.001). A total of 144 patients with stable and asymptomatic brain metastases were also eligible. Median PFS for this subset of patients treated with osimertinib and chemotherapy was 8.5 months and 4.2 months, respectively (HR 0.32 [95% CI 0.21 to 0.49]). In the AURA3 trial, osimertinib was better tolerated than chemotherapy, with 23% of patients treated with osimertinib experiencing grade 3 or 4 AEs as compared to 47% of chemotherapy-treated patients. The most common AEs of any grade were diarrhea (41%), rash (34%), dry skin (23%), and paronychia (22%).⁶⁰

For the case patient, a reasonable approach would be to obtain a tissue biopsy of the adrenal mass and more importantly to check for the T790M mutation. Similar to the companion diagnostic for EGFR mutations, the cobas EGFR mutation test v2 is the FDA-approved test for T790M. However, if this resistance mutation is detected by any CLIA-certified laboratories, osimertinib should be the recommended treatment option. If tissue biopsy is not feasible, plasma-based testing should be considered. A blood-based companion diagnostic also is FDA approved.

ALK REARRANGEMENTS

CASE 2 PRESENTATION

A 42-year-old Korean woman who is a non-smoker with no significant past medical history presents with fatigue, unintentional weight loss of 20 lb in the past 4 months, and vague abdominal pain. A CT can of the abdomen and pelvis without contrast shows multiple foci in the liver and an indeterminate nodule in the right lung base. She subsequently undergoes PET/CT, which confirms multiple liver nodules/masses ranging from 1 to 3 cm with moderate FDG uptake. In addition, there is a 3.5-cm pleura-based lung mass on the right side with moderate FDG uptake. MRI-brain with and without contrast is negative for malignancy. A CT-guided biopsy of 1 of the liver masses is ordered and pathology returns positive for poorly differentiated adenocarcinoma consistent with lung primary. Molecular analysis reveals an echinoderm microtubule-associated protein-like 4 (EML4)-ALK rearrangement. She is placed on crizotinib by an outside oncologist and after about 3 weeks of therapy is doing well. She is now in your clinic for a second opinion. She says that some of her friends told her about another medication called ceritinib and was wondering if she would need to switch her cancer treatment.

• How would you respond to this patient’s inquiry?

FIRST-LINE TKIS FOR ALK REARRANGEMENTS

ALK rearrangements are found in 2% to 7% of NSCLC, with EML4-ALK being the most prevalent fusion variant.⁶¹ The inversion of chromosome 2p leads to the fusion of the EML4 gene and the ALK gene, which causes the constitutive activation of the fusion protein and ultimately increased transformation and tumorigenicity.^7,61 Patients harboring ALK rearrangements tend to be non-smokers. Adenocarcinoma, especially signet ring cell subtype, is the predominant histology. Compared to EGFR mutations, patients with ALK mutations are significantly younger and more likely to be men.⁶²ALK rearrangements can be detected by either FISH or IHC, and most next-generation sequencing (NGS) panels have the ability to identify this driver mutation.

Crizotinib is the first approved ALK inhibitor for the treatment of NSCLC in this molecular subset of patients.⁶³ PROFILE 1014 is a phase 3 randomized trial that compared crizotinib with chemotherapy containing platinum/pemetrexed for up to 6 cycles. Crossover to crizotinib was allowed for patients with disease progression on chemotherapy. The primary end point was PFS by independent radiologic review. The crizotinib arm demonstrated superior PFS (10.9 months versus 7 months; HR 0.45 [95% CI 0.35 to 0.6], P < 0.001) and ORR (74% versus 45%, P < 0.001). Median survival was not reached in either arm (HR 0.82 [95% CI 0.54 to 1.26], P = 0.36).⁶⁴ Based on this international trial, crizotinib is considered standard of care in the United States for treatment-naïve patients with advanced NSCLC harboring ALK rearrangements. The current recommended dose is 250 mg orally twice daily. Common treatment-related AEs of all grades include vision disorder (62%), nausea (53%), diarrhea (43%), vomiting (40%), edema (28%), and constipation (27%).⁶⁵ PROFILE 1007 compared crizotinib with pemetrexed or docetaxel in ALK-rearranged NSCLC patients with prior exposure to 1 platinum-based chemotherapy. The median PFS was 7.7 months for crizotinib as compared to 3 months for chemotherapy (HR 0.49 [95% CI 0.37 to 0.64], P < 0.001). The response rates were 65% and 20% for crizotinib and chemotherapy, respectively (P < 0.001).⁶⁶ In other countries, crizotinib following 1 prior platinum-based regimen may be considered standard of care based on this trial.

Ceritinib is an oral second-generation ALK inhibitor that is 20 times more potent than crizotinib based on enzymatic assays.⁶⁷ It also targets ROS1 and insulin-like growth factor 1 receptor but not c-MET. It was first approved by the FDA in April 2014 for metastatic ALK-rearranged NSCLC following crizotinib.⁶⁸ In May 2017, the FDA granted approval of ceritinib for treatment-naïve patients. This decision was based on the results of the ASCEND-4 trial, a randomized phase 3 trial assessing the efficacy and safety of ceritinib over chemotherapy in the first-line setting. The trial assigned 376 patients to either ceritinib at 750 mg once daily or platinum/pemetrexed for 4 cycles followed by maintenance pemetrexed. Median PFS was 16.6 months for ceritinib versus 8.1 months for chemotherapy (HR 0.55 [95% CI 0.42 to 0.73]; P < 0.00001).⁶⁹ Toxicities of ceritinib are not negligible, with gastrointestinal toxicity being the most prevalent. For instance, diarrhea, nausea, vomiting, abdominal pain, and constipation of all grades were seen in 86%, 80%, 60%, 54%, and 29% of patients, respectively. Furthermore, fatigue and decreased appetite occurred in 52% and 34% of patients, respectively. In terms of laboratory abnormalities, 84% of patients experienced decreased hemoglobin of all grades; 80% increased ALT; 75% increased AST; 58% increased creatinine; 49% increased glucose; 36% decreased phosphate; and 28% increased lipase. Due to these AEs, the incidence of dose reduction was about 58% and the median onset was around 7 weeks.⁷⁰

Alectinib is another oral second-generation ALK inhibitor that was approved by the FDA in December 2015 for the treatment of NSCLC patients with ALK rearrangements who have progressed on or are intolerant to crizotinib.⁷¹ Its indication will soon be broadened to the first-line setting based on the ALEX trial.⁷² Alectinib is a potent and highly selective TKI of ALK⁷³ with activity against known resistant mutations to crizotinib.^74,75 It also inhibits RET but not ROS1 or c-MET.⁷⁶ ALEX, a randomized phase 3 study, compared alectinib with crizotinib in treatment-naïve patients with NSCLC harboring ALK rearrangements. The trial enrolled 303 patients and the median follow-up was approximately 18 months. The alectinib arm (600 mg twice daily) demonstrated significantly higher PFS by investigator-assessment, the trial’s primary end point. The 12-month event-free survival was 68.4% (95% CI 61% to 75.9%) versus 48.7% (95% CI 40.4% to 56.9%) for alectinib and crizotinib, respectively (HR 0.47 [95% CI 0.34 to 0.65], P < 0.001). The median PFS was not reached in the alectinib arm (95% CI 17.7 months to not estimable) as compared to 11.1 months in the crizotinib arm (95% CI 9.1 to 13.1 months).⁷² Alectinib is generally well tolerated. Common AEs of all grades include fatigue (41%), constipation (34%), edema (30%), and myalgia (29%). As alectinib can cause anemia, lymphopenia, hepatic toxicity, increased creatine phosphokinase, hyperglycemia, electrolyte abnormalities, and increased creatinine, periodic monitoring of these laboratory values is important, although most of these abnormalities are grade 1 or 2.⁷⁷

Brigatinib, another oral second-generation ALK inhibitor, was granted accelerated approval by the FDA in April 2017 for ALK-rearranged and crizotinib-resistant NSCLC based on the ALTA trial. This randomized phase 2 study of brigatinib showed an ORR by investigator assessment of 54% (97.5% CI 43% to 65%) in the 180 mg once daily arm with lead-in of 90 mg once daily for 7 days. Median PFS was 12.9 months (95% CI 11.1 months to not reached [NR]).⁷⁸ Currently, a phase 3 study of brigatinib versus crizotinib in ALK inhibitor–naïve patients is recruiting participants (ALTA-1L). It will be interesting to see if brigatinib can achieve a front-line indication.

Starting the case patient on crizotinib is well within the treatment guidelines. One may consider ceritinib or alectinib in the first-line setting, but both TKIs can be reserved upon disease progression. We would recommend a repeat biopsy at that point to look for resistant mechanisms, as certain secondary ALK mutations may be rescued by certain next-generation ALK inhibitors. For instance, the F1174V mutation has been reported to confer resistance to ceritinib but sensitivity to alectinib, while the opposite is true for I1171T. The G1202R mutation is resistant to ceritinib, alectinib, and brigatinib, but lorlatinib, a third-generation ALK inhibitor, has shown activity against this mutation.⁷⁹ Furthermore, brain metastasis represents a treatment challenge for patients with ALK rearrangements. It is also an efficacy measure of next-generation ALK inhibitors, all of which have demonstrated better central nervous system activity than crizotinib.^69,78,80 If the case patient were found to have brain metastasis at the initial diagnosis, either ceritinib or alectinib would be a reasonable choice since crizotinib has limited penetration of blood-brain barrier.⁸¹

ROS1 REARRANGEMENTS

CASE PRESENTATION 3

A 66-year-old Chinese woman who is a non-smoker with a past medical history of hypertension and hypothyroidism presents to the emergency department for worsening lower back pain. Initial workup includes x-ray of the lumbar spine followed by MRI with contrast, which shows a soft tissue mass at L3-4 without cord compression. CT of the chest, abdomen, and pelvis with contrast shows a 7-cm right hilar mass, bilateral small lung nodules, mediastinal lymphadenopathy, and multiple lytic lesions in ribs, lumbar spine, and pelvis. MRI-brain with and without contrast is negative for malignancy. She undergoes endo-bronchial ultrasound and biopsy of the right hilar mass, which shows poorly differentiated adenocarcinoma. While waiting for the result of the molecular analysis, the patient undergoes palliative radiation therapy to L2-5 with good pain relief. She is discharged from the hospital and presents to your clinic for follow up. Molecular analysis now reveals ROS1 rearrangement with CD74-ROS1 fusion.

• What treatment plan should be put in place for this patient?

FIRST-LINE THERAPY FOR ROS1 REARRANGEMENTS

Approximately 2.4% of lung adenocarcinomas harbor ROS1 rearrangements.⁸² This distinct genetic alteration occurs more frequently in NSCLC patients who are younger, female, and never-smokers, and who have adenocarcinomas.⁸ It has been shown that ROS1 rearrangements rarely overlap with other genetic alterations including KRAS mutations, EGFR mutations, and ALK rearrangements.⁸³ As a receptor tyrosine kinase, ROS1 is similar to ALK and insulin receptor family members.⁸⁴ Crizotinib, which targets ALK, ROS1, and c-MET, was approved by the FDA on March 11, 2016, for the treatment of metastatic ROS1-rearranged NSCLC.⁸⁵ The approval was based on a phase 2 expansion cohort of the original phase 1 study. Among 50 US patients enrolled in this expansion cohort, 3 had complete responses and 33 had partial responses with ORR of 72% (95% CI 58% to 84%). Median PFS was 19.2 months (95% CI 14.4 months to NR) and median duration of response (DOR) was 17.6 months (95% CI 14.5 months to NR).⁸⁶ During longer follow-up, independent radiology review confirmed high ORR of 66% and median DOR of 18.3 months.⁸⁵

Interestingly, no companion diagnostic assay has been approved for the detection of ROS1 rearrangements with the approval of crizotinib. In the United States, break apart FISH is the most common detection method. In fact, in the above mentioned phase 2 study, ROS1 rearrangements were detected in 49 out of 50 patients by this method.⁸⁶ FISH can be technically challenging when dealing with high volume and multiple targets. Reverse transcriptase-PCR is another detection method, but it requires knowledge of the fusion partners. To date, at least 14 ROS1 fusion partners have been reported, with CD74 being the most common.⁸⁷ NGS with appropriate design and validation can also be used to detect ROS1 rearrangements.

For the case patient, the recommendation would be to start her on crizotinib at 250 mg twice daily. Monitoring for vision disturbance, gastrointestinal complaints, and edema is warranted. Because the estimated onset of response is around 7.9 weeks,⁸⁶ plans should be made to repeat her scans in approximately 2 months.

BRAF V600E MUTATIONS

CASE PRESENTATION 4

A 71-year-old Caucasian man with a past medical history of hypertension, dyslipidemia, and ischemic cerebrovascular accident without residual deficits was diagnosed with stage IV adenocarcinoma of the lung about 8 months ago. He has a 40 pack-year smoking history and quit smoking when he was diagnosed with lung cancer. His disease burden involved a large mediastinal mass, scattered pleural nodules, multiple lymphadenopathy, and several soft tissue masses. His outside oncologist started him on chemotherapy containing carboplatin and pemetrexed for 6 cycles followed by maintenance pemetrexed. The most recent restaging scans show disease progression with enlarging soft tissue masses and several new lytic bone lesions. MRI-brain with and without contrast shows 2 subcentimeter enhancing lesions. He transferred care to you approximately 4 weeks ago. You ordered a repeat biopsy of 1 of the enlarging soft tissue masses. Molecular analysis revealed BRAF V600E mutation. In the interim, he underwent stereotactic radiosurgery for the 2 brain lesions without any complications. The patient is now in your clinic for follow up.

• What would be your recommended systemic treatment?

TARGETED THERAPIES FOR BRAF V600E MUTATION

BRAF mutations were first recognized as activating mutations in advanced melanomas, with BRAF V600E, resulting from the substitution of glutamic acid for valine at amino acid 600, being the most common. BRAF plays an important role in the mitogen-activated protein kinase (MAPK) signaling pathway. Briefly, the activation of MAPK pathway occurs upon ligand binding of receptor tyrosine kinases, which then involves RAS/BRAF/MEK/ERK in a stepwise manner, ultimately leading to cell survival. BRAF mutations have been increasingly recognized also as driver mutations in NSCLC.^9–12 They can be detected by PCR or NGS method. The characteristics of NSCLC patients harboring BRAF mutations have been described by various groups.^9–12 For instance, 1 case series showed that the incidence was 2.2% among patients with advanced lung adenocarcinoma; 50% of mutations were V600E, while G469A and D594G accounted for the remaining 39% and 11% of patients, respectively. All patients were either current or former smokers. The median OS of patients with BRAF mutations in this case series was NR, while it was 37 months for patients with EGFR mutations (P = 0.73) and NR for patients with ALK rearrangements (P = 0.64).⁹

For patients with BRAF V600E–mutant NSCLC who have progressed on platinum-based chemotherapy, the combination of dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor) may represent a new treatment paradigm. This was illustrated in a phase 2, nonrandomized, open-label study. A total of 57 patients were enrolled and 36 patients (63.2% [95% CI 49.3% to 75.6%]) achieved an overall response by investigator assessment, the trial’s primary end point. Disease control rate was 78.9% (95% CI 66.1% to 88.6%), with 4% complete response, 60% partial response, and 16% stable disease. PFS was 9.7 months (95% CI [6.9 to 19.6 months]). The safety profile was comparable to what had been observed in patients with melanoma treated with this regimen. More specifically, 56% of patients on this trial reported serious AEs, including pyrexia (16%), anemia (5%), confusional state (4%), decreased appetite (4%), hemoptysis (4%), hypercalcemia (4%), nausea (4%), and cutaneous squamous cell carcinoma (4%). In addition, neutropenia (9%) and hyponatremia (7%) were the most common grade 3-4 AEs.¹⁶

The case patient has experienced disease progression after 1 line of platinum-based chemotherapy, so the combination of dabrafenib and trametinib would be a robust systemic treatment option. dabrafenib as a single agent has also been studied in BRAF V600E–mutant NSCLC in a phase 2 trial. The overall response by investigator assessment among 84 patients was 33% (95% CI 23% to 45%).¹⁴ Vemurafenib, another oral BRAF TKI, has demonstrated efficacy for NSCLC patients harboring BRAF V600E mutation. In the cohort of 20 patients with NSCLC, the response rate was 42% (95% CI 20% to 67%) and median PFS was 7.3 months (95% CI 3.5 to 10.8 months).¹³ Patients with non-V600E mutations have shown variable responses to targeted therapies. MEK TKIs may be considered in this setting; however, the details of this discussion are beyond the scope of this review.

CONCLUSION

The management of advanced NSCLC with driver mutations has seen revolutionary changes over the past decade. Tremendous research has been done in order to first understand the molecular pathogenesis of NSCLC and then discover driver mutations that would lead to development of targeted therapies with clinically significant efficacy as well as tolerability. More recently, increasing efforts have focused on how to conquer acquired resistance in patients with disease progression after first-line TKIs. The field of EGFR-mutant NSCLC has set a successful example, but the work is nowhere near finished. The goals are to search for more driver mutations and to design agents that could potentially block cell survival signals once and for all.

INTRODUCTION

Lung cancer is the second most common type of cancer in the United States, with 222,500 estimated new cases in 2017, according to the American Cancer Society.¹ However, it is by far the number one cause of death due to cancer, with an estimated 155,870 lung cancer–related deaths occurring in 2017, which is higher than the number of deaths due to breast cancer, prostate cancer, and colorectal cancer combined.^1,2 Despite slightly decreasing incidence and mortality over the past decade, largely due to smoking cessation, the 5-year survival rate of lung cancer remains dismal at approximately 18%.^2–4

Non-small cell lung cancer (NSCLC) accounts for 80% to 85% of all lung cancer cases.⁴ Traditionally, it is further divided based on histology: adenocarcinoma, squamous cell carcinoma, large cell carcinoma, and not otherwise specified.⁵ Chemotherapy had been the cornerstone of treatment for stage IV NSCLC. It is not target-specific and is most effective against rapidly growing cells. Common adverse effects include alopecia, nausea/vomiting, myelosuppression, cardiotoxicity, neuropathy, and nephrotoxicity. However, this paradigm has shifted following the discovery of mutations of the epidermal growth factor receptor (EGFR) gene as an oncogenic driver that confers sensitivity to small molecule tyrosine kinase inhibitors (TKIs) targeting EGFR.⁶ The EGFR inhibitors are given orally and have a spectrum of toxicities (eg, such as rash, diarrhea, and elevated transaminases) different from that of systemic chemotherapy, which is often administered intravenously. Following the discovery of EGFR mutations, rearrangements of the anaplastic lymphoma kinase (ALK) gene⁷ and ROS1 gene⁸ were identified as targetable driver mutations in NSCLC. The frequency of both rearrangements is lower than that of EGFR mutations. Additionally, BRAF V600E mutation has been identified in NSCLC.^9–12 This activation mutation is commonly seen in melanoma. Agents that have already been approved for the treatment of melanoma with the BRAF V600E mutation are being tested in NSCLC patients with this mutation.^13–16

Given the effectiveness and tolerability of targeted therapy, identifying this distinct molecular subset of NSCLC patients is critical in treatment. Currently, molecular testing is mandatory in all stage IV patients with non-squamous cell carcinoma, as a preponderance of patients with driver mutations have this histology subtype.^5,17–19 For patients with squamous cell carcinoma, molecular testing should be considered if the biopsy specimen is small, there is mixed histology, or the patient is a nonsmoker.^5,20 Several techniques are commonly utilized in detecting these genetic alterations. EGFR mutation can be detected by polymerase chain reaction (PCR), ALK or ROS1 rearrangement can be detected by fluorescence in-situ hybridization (FISH), and immunohistochemistry (IHC) can also be used to detect ALK rearrangement. The current guideline is to use comprehensive genomic profiling to capture all the potential molecular targets simultaneously instead of running stepwise tests just for EGFR, ALK, and ROS1.⁵BRAF V600E mutation,^13–16 MET exon 14 skipping mutation,^21–24 RET rearrangements,^25–27 and HER2 mutations^28–30 are among the emergent genetic alterations with various responses to targeted therapy.³¹ Some of these targeted agents have been approved for other types of malignancy, and others are still in the development phase.

Several initiatives worldwide have reported better outcomes of patients with driver mutations treated with targeted therapy. For instance, the Lung Cancer Mutation Consortium in the United States demonstrated that the median survival of patients without driver mutations, with drivers mutations but not treated with targeted therapy, and with driver mutations and treated with targeted therapy was 2.08 years, 2.38 years, and 3.49 years, respectively.³² The French Cooperative Thoracic Intergroup-French National Cancer Institute demonstrated that the median survival for patients with driver mutations versus those without driver mutations was 16.5 months versus 11.8 months.³³ The Spanish Lung Cancer Group demonstrated that the overall survival (OS) for patients with EGFR mutations treated with erlotinib was 27 months.³⁴ The mutations in lung cancer, their frequencies, and the downstream signaling pathways are depicted in the Figure.³⁵

In this article, we discuss targeted therapy for patients with EGFR mutations, ALK rearrangements, ROS1 rearrangements, and BRAF V600E mutation. We also discuss the management of patients with EGFR mutations who develop a secondary mutation after TKI therapy. Almost all of the targeted agents discussed herein have been approved by the US Food and Drug Administration (FDA), so they are considered standard of care. All available phase 3 trials pertinent to these targeted therapies are included in the discussion.

EGFR MUTATIONS

CASE PRESENTATION 1

A 54-year-old Caucasian man who is a former smoker with a 10 pack-year history and past medical history of hypertension and dyslipidemia presents with progressive dyspnea for several weeks. A chest x-ray shows moderate pleural effusion on the left side with possible mass-like opacity on the left upper lung field. An ultrasound-guided thoracentesis is performed and cytology is positive for adenocarcinoma of likely pulmonary origin. Staging workup including positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging of the brain with and without contrast is done. PET/CT shows a 5.5-cm mass in the left upper lobe of the lung with high fluorodeoxyglucose (FDG) uptake, several 1- to 2-cm mediastinal lymph nodes with moderate FDG uptake, and small pleural effusion on both sides with moderate FDG uptake. MRI-brain is negative for malignancy. The patient subsequently undergoes a CT-guided biopsy of the lung mass, which shows moderately differentiated adenocarcinoma. Comprehensive molecular profiling reveals EGFR L858R mutation only. The patient now presents for the initial consultation. Of note, his Eastern Cooperative Oncology Group performance status is 1.

• What is the next step in the management of this patient?

FIRST-LINE TKI FOR SENSITIZING EGFR MUTATIONS

The 2 most common EGFR mutations are deletions in exon 19 and substitution of arginine for leucine in exon 21 (L858R), found in approximately 45% and 40% of patients with EGFR mutations, respectively.³⁶ Both mutations are sensitive to EGFR TKIs. The benefit may be greater in patients with exon 19 deletions as compared to exon 21 L858R substitution,^37,38 but this has not been demonstrated consistently in clinical trials.^39-43 In the United States, EGFR mutations are found in approximately 10% of patients with NSCLC, while the incidence can be as high as 50% in Asia.⁴⁴ Even though the cobas EGFR mutation test is the companion diagnostic approved by the US FDA, a positive test result from any laboratory with the Clinical Laboratory Improvement Amendments (CLIA) certificate should prompt the use of an EGFR TKI as the initial treatment.

Three EGFR TKIs that have been approved as first-line therapy in the United States are available: erlotinib, afatinib, and gefitinib.⁵ Both erlotinib and gefitinib are considered first-generation TKIs. They have higher binding affinity for the 2 common EGFR mutations than wild-type EGFR. In addition, they reversibly bind to the intracellular tyrosine kinase domain, resulting in inhibition of autophosphorylation of the tyrosine residues. Afatinib, a second-generation and irreversible TKI, targets EGFR (HER1) as well as HER2 and HER4.⁴⁵

The superior efficacy of the EGFR TKIs over platinum doublet chemotherapy in treatment-naïve patients with EGFR mutations has been demonstrated in 7 randomized trials to date (Table).⁴⁶ Erlotinib was the TKI arm for the OPTIMAL,⁴¹ EURTAC,⁴² and ENSURE trials;³⁸ afatinib was the TKI arm for LUX-LUNG 3³⁷ and 6;⁴³ gefitinib was the TKI arm for NEJ002^39,47 and WJTOG3405.⁴⁰ A meta-analysis of these 7 trials by Lee et al showed that progression-free survival (PFS) was significantly prolonged by EGFR TKIs (hazard ratio [HR] 0.37 [95% confidence interval {CI} 0.32 to 0.42]).⁴⁶ For instance, in the EURTAC trial, median PFS was 9.7 months for patients treated with erlotinib as compared to 5.2 months for patients treated with platinum/gemcitabine or platinum/docetaxel.⁴² In this meta-analysis, prespecified subgroups included age, sex, ethnicity, smoking status, performance status, tumor histology, and EGFR mutation subtype. The superior outcome with TKIs was observed in all subgroups. Furthermore, patients with exon 19 deletions, nonsmokers, and women had even better outcomes.⁴⁶

Erlotinib is the most commonly used TKI in the United States largely because gefitinib was off the market for some time until it was re-approved by the FDA in 2015. Interestingly, this “re-approval” was not based on either 1 of the 2 prospective trials (NEJ002^39,47 and WJTOG3405⁴⁰), but rather was based on an exploratory analysis of the IPASS trial^48,49 as well as a prospective phase 4, single-arm trial in Europe (IFUM).⁵⁰ The superior efficacy of gefitinib over carboplatin/paclitaxel among patients with EGFR mutations in the IPASS trial was confirmed by blind independent central review, with longer PFS (HR 0.54 [95% CI 0.38 to 0.79] P = 0.0012) and higher objective response rate (ORR; odds ratio 3 [95% CI 1.63 to 5.54], P = 0.0004).⁴⁹

CASE 1 CONTINUED

Based on the EGFR L858R mutation status, the patient is started on erlotinib. He is quite happy that he does not need intravenous chemotherapy but wants to know what toxicities he might potentially have with erlotinib.

• What are the common adverse effects (AEs) of EGFR TKIs? How are AEs of TKIs managed?

Safety Profile

The important toxicities associated with EGFR TKIs are rash, gastrointestinal toxicity, hepatic toxicity, and pulmonary toxicity. Rash is an AE specific to all agents blocking the EGFR pathway, including small molecules and monoclonal antibodies such as cetuximab. The epidermis has a high level of expression of EGFR, which contributes to this toxicity.⁵¹ Rash usually presents as dry skin or acneiform eruption. Prophylactic treatment with oral tetracyclines and topical corticosteroids is generally recommended upon initiation of TKI therapy. Diarrhea is the most prevalent gastrointestinal toxicity. All patients starting treatment should be given prescriptions to manage diarrhea such as loperamide and be advised to call when it occurs. Hepatic toxicity is often manifested as elevated transaminases or bilirubin. Interstitial lung disease (ILD) is a rare but potentially fatal pulmonary toxicity.

Rash of any grade was reported in 49.2% of patients treated with erlotinib in clinical trials, while grade 3 rash occurred in 6% of patients and no grade 4 was reported. Diarrhea of any grade was reported in 20.3% of patients, grade 3 diarrhea occurred in 1.8%, and no grade 4 was reported. Grade 2 and 3 alanine aminotransferase (ALT) elevations were seen in 2% and 1% of patients, respectively. Grade 2 and 3 bilirubin elevations were seen in 4% and less than 1% of patients, respectively. The incidence of serious ILD-like events was less than 1%.⁵²

Afatinib is associated with higher incidences of rash and diarrhea. Specifically, diarrhea and rash of all grades were reported in 96% and 90% of patients treated with afatinib, respectively. Paronychia of all grades occurred in 58% of patients. Elevated ALT of all grades was seen in 11% of patients. Approximately 1.5% of patients treated with afatinib across clinical trials had ILD or ILD-like AEs.⁵³

Gefitinib, the most commonly used TKI outside United States, has a toxicity profile similar to erlotinib, except for hepatic toxicity. For instance, rash of all grades occurred in 47% of patients, diarrhea of all grades occurred in 29% of patients, and ILD or ILD-like AEs occurred in 1.3% of patients across clinical trials. In comparison, elevated ALT and aspartate aminotransferase (AST) of all grades was seen in 38% and 40% of patients, respectively.⁵⁴ Therefore, close monitoring of liver function is clinically warranted. In particular, patients need to be advised to avoid concomitant use of herbal supplements, a common practice in Asian countries.

CASE 1 CONTINUED

The patient does well while on erlotinib at 150 mg orally once daily for about 8 months, until he develops increasing abdominal pain. A CT scan of the abdomen and pelvis with contrast shows a new 8-cm right adrenal mass. Additionally, a repeat CT scan of the chest with contrast shows a stable lung mass but enlarging mediastinal lymphadenopathy.

• How would you manage the patient at this point?

MANAGEMENT OF T790M MUTATION AFTER PROGRESSION ON FIRST-LINE EGFR TKIS

As mentioned above, the median PFS of patients with EGFR mutations treated with 1 of the 3 TKIs is around 9 to 13 months.⁴⁶ Of the various resistance mechanisms that have been described, the T790M mutation is found in approximately 60% of patients who progress after treatment with first-line TKIs.^55,56 Other mechanisms, such as HER2 amplification, MET amplification, or rarely small cell transformation, have been reported.⁵⁶ The first- and second-generation EGFR TKIs function by binding to the ATP-binding domain of mutated EGFR, leading to inhibition of the downstream signaling pathways (Figure, part B) and ultimately cell death.³⁵ The T790M mutation hinders the interaction between the ATP-binding domain of EGFR kinase and TKIs, resulting in treatment resistance and disease progression.^57,58

Osimertinib is a third-generation irreversible EGFR TKI with activity against both sensitizing EGFR and resistant T790M mutations. It has low affinity for wide-type EGFR as well as insulin receptor and insulin-like growth factor receptor.⁵⁹ Osimertinib has been fully approved for NSCLC patients with EGFR mutations who have progressed on first-line EGFR TKIs with the development of T790M mutation. An international phase 3 trial (AURA3) randomly assigned 419 patients in a 2:1 ratio to either osimertinib or platinum/pemetrexed. Eligible patients all had the documented EGFR mutations and disease progression after first-line EGFR TKIs. Central confirmation of the T790M mutation was required. Median PFS by investigator assessment, the trial’s primary end point, was 10.1 months for osimertinib versus 4.4 months for chemotherapy (HR 0.3 [95% CI 0.23 to 0.41]; P < 0.001). ORR was 71% for osimertinib versus 31% for chemotherapy (HR 5.39 [95% CI 3.47 to 8.48], P < 0.001). A total of 144 patients with stable and asymptomatic brain metastases were also eligible. Median PFS for this subset of patients treated with osimertinib and chemotherapy was 8.5 months and 4.2 months, respectively (HR 0.32 [95% CI 0.21 to 0.49]). In the AURA3 trial, osimertinib was better tolerated than chemotherapy, with 23% of patients treated with osimertinib experiencing grade 3 or 4 AEs as compared to 47% of chemotherapy-treated patients. The most common AEs of any grade were diarrhea (41%), rash (34%), dry skin (23%), and paronychia (22%).⁶⁰

For the case patient, a reasonable approach would be to obtain a tissue biopsy of the adrenal mass and more importantly to check for the T790M mutation. Similar to the companion diagnostic for EGFR mutations, the cobas EGFR mutation test v2 is the FDA-approved test for T790M. However, if this resistance mutation is detected by any CLIA-certified laboratories, osimertinib should be the recommended treatment option. If tissue biopsy is not feasible, plasma-based testing should be considered. A blood-based companion diagnostic also is FDA approved.

ALK REARRANGEMENTS

CASE 2 PRESENTATION

A 42-year-old Korean woman who is a non-smoker with no significant past medical history presents with fatigue, unintentional weight loss of 20 lb in the past 4 months, and vague abdominal pain. A CT can of the abdomen and pelvis without contrast shows multiple foci in the liver and an indeterminate nodule in the right lung base. She subsequently undergoes PET/CT, which confirms multiple liver nodules/masses ranging from 1 to 3 cm with moderate FDG uptake. In addition, there is a 3.5-cm pleura-based lung mass on the right side with moderate FDG uptake. MRI-brain with and without contrast is negative for malignancy. A CT-guided biopsy of 1 of the liver masses is ordered and pathology returns positive for poorly differentiated adenocarcinoma consistent with lung primary. Molecular analysis reveals an echinoderm microtubule-associated protein-like 4 (EML4)-ALK rearrangement. She is placed on crizotinib by an outside oncologist and after about 3 weeks of therapy is doing well. She is now in your clinic for a second opinion. She says that some of her friends told her about another medication called ceritinib and was wondering if she would need to switch her cancer treatment.

• How would you respond to this patient’s inquiry?

FIRST-LINE TKIS FOR ALK REARRANGEMENTS

ALK rearrangements are found in 2% to 7% of NSCLC, with EML4-ALK being the most prevalent fusion variant.⁶¹ The inversion of chromosome 2p leads to the fusion of the EML4 gene and the ALK gene, which causes the constitutive activation of the fusion protein and ultimately increased transformation and tumorigenicity.^7,61 Patients harboring ALK rearrangements tend to be non-smokers. Adenocarcinoma, especially signet ring cell subtype, is the predominant histology. Compared to EGFR mutations, patients with ALK mutations are significantly younger and more likely to be men.⁶²ALK rearrangements can be detected by either FISH or IHC, and most next-generation sequencing (NGS) panels have the ability to identify this driver mutation.

Crizotinib is the first approved ALK inhibitor for the treatment of NSCLC in this molecular subset of patients.⁶³ PROFILE 1014 is a phase 3 randomized trial that compared crizotinib with chemotherapy containing platinum/pemetrexed for up to 6 cycles. Crossover to crizotinib was allowed for patients with disease progression on chemotherapy. The primary end point was PFS by independent radiologic review. The crizotinib arm demonstrated superior PFS (10.9 months versus 7 months; HR 0.45 [95% CI 0.35 to 0.6], P < 0.001) and ORR (74% versus 45%, P < 0.001). Median survival was not reached in either arm (HR 0.82 [95% CI 0.54 to 1.26], P = 0.36).⁶⁴ Based on this international trial, crizotinib is considered standard of care in the United States for treatment-naïve patients with advanced NSCLC harboring ALK rearrangements. The current recommended dose is 250 mg orally twice daily. Common treatment-related AEs of all grades include vision disorder (62%), nausea (53%), diarrhea (43%), vomiting (40%), edema (28%), and constipation (27%).⁶⁵ PROFILE 1007 compared crizotinib with pemetrexed or docetaxel in ALK-rearranged NSCLC patients with prior exposure to 1 platinum-based chemotherapy. The median PFS was 7.7 months for crizotinib as compared to 3 months for chemotherapy (HR 0.49 [95% CI 0.37 to 0.64], P < 0.001). The response rates were 65% and 20% for crizotinib and chemotherapy, respectively (P < 0.001).⁶⁶ In other countries, crizotinib following 1 prior platinum-based regimen may be considered standard of care based on this trial.

Ceritinib is an oral second-generation ALK inhibitor that is 20 times more potent than crizotinib based on enzymatic assays.⁶⁷ It also targets ROS1 and insulin-like growth factor 1 receptor but not c-MET. It was first approved by the FDA in April 2014 for metastatic ALK-rearranged NSCLC following crizotinib.⁶⁸ In May 2017, the FDA granted approval of ceritinib for treatment-naïve patients. This decision was based on the results of the ASCEND-4 trial, a randomized phase 3 trial assessing the efficacy and safety of ceritinib over chemotherapy in the first-line setting. The trial assigned 376 patients to either ceritinib at 750 mg once daily or platinum/pemetrexed for 4 cycles followed by maintenance pemetrexed. Median PFS was 16.6 months for ceritinib versus 8.1 months for chemotherapy (HR 0.55 [95% CI 0.42 to 0.73]; P < 0.00001).⁶⁹ Toxicities of ceritinib are not negligible, with gastrointestinal toxicity being the most prevalent. For instance, diarrhea, nausea, vomiting, abdominal pain, and constipation of all grades were seen in 86%, 80%, 60%, 54%, and 29% of patients, respectively. Furthermore, fatigue and decreased appetite occurred in 52% and 34% of patients, respectively. In terms of laboratory abnormalities, 84% of patients experienced decreased hemoglobin of all grades; 80% increased ALT; 75% increased AST; 58% increased creatinine; 49% increased glucose; 36% decreased phosphate; and 28% increased lipase. Due to these AEs, the incidence of dose reduction was about 58% and the median onset was around 7 weeks.⁷⁰

Alectinib is another oral second-generation ALK inhibitor that was approved by the FDA in December 2015 for the treatment of NSCLC patients with ALK rearrangements who have progressed on or are intolerant to crizotinib.⁷¹ Its indication will soon be broadened to the first-line setting based on the ALEX trial.⁷² Alectinib is a potent and highly selective TKI of ALK⁷³ with activity against known resistant mutations to crizotinib.^74,75 It also inhibits RET but not ROS1 or c-MET.⁷⁶ ALEX, a randomized phase 3 study, compared alectinib with crizotinib in treatment-naïve patients with NSCLC harboring ALK rearrangements. The trial enrolled 303 patients and the median follow-up was approximately 18 months. The alectinib arm (600 mg twice daily) demonstrated significantly higher PFS by investigator-assessment, the trial’s primary end point. The 12-month event-free survival was 68.4% (95% CI 61% to 75.9%) versus 48.7% (95% CI 40.4% to 56.9%) for alectinib and crizotinib, respectively (HR 0.47 [95% CI 0.34 to 0.65], P < 0.001). The median PFS was not reached in the alectinib arm (95% CI 17.7 months to not estimable) as compared to 11.1 months in the crizotinib arm (95% CI 9.1 to 13.1 months).⁷² Alectinib is generally well tolerated. Common AEs of all grades include fatigue (41%), constipation (34%), edema (30%), and myalgia (29%). As alectinib can cause anemia, lymphopenia, hepatic toxicity, increased creatine phosphokinase, hyperglycemia, electrolyte abnormalities, and increased creatinine, periodic monitoring of these laboratory values is important, although most of these abnormalities are grade 1 or 2.⁷⁷

Brigatinib, another oral second-generation ALK inhibitor, was granted accelerated approval by the FDA in April 2017 for ALK-rearranged and crizotinib-resistant NSCLC based on the ALTA trial. This randomized phase 2 study of brigatinib showed an ORR by investigator assessment of 54% (97.5% CI 43% to 65%) in the 180 mg once daily arm with lead-in of 90 mg once daily for 7 days. Median PFS was 12.9 months (95% CI 11.1 months to not reached [NR]).⁷⁸ Currently, a phase 3 study of brigatinib versus crizotinib in ALK inhibitor–naïve patients is recruiting participants (ALTA-1L). It will be interesting to see if brigatinib can achieve a front-line indication.

Starting the case patient on crizotinib is well within the treatment guidelines. One may consider ceritinib or alectinib in the first-line setting, but both TKIs can be reserved upon disease progression. We would recommend a repeat biopsy at that point to look for resistant mechanisms, as certain secondary ALK mutations may be rescued by certain next-generation ALK inhibitors. For instance, the F1174V mutation has been reported to confer resistance to ceritinib but sensitivity to alectinib, while the opposite is true for I1171T. The G1202R mutation is resistant to ceritinib, alectinib, and brigatinib, but lorlatinib, a third-generation ALK inhibitor, has shown activity against this mutation.⁷⁹ Furthermore, brain metastasis represents a treatment challenge for patients with ALK rearrangements. It is also an efficacy measure of next-generation ALK inhibitors, all of which have demonstrated better central nervous system activity than crizotinib.^69,78,80 If the case patient were found to have brain metastasis at the initial diagnosis, either ceritinib or alectinib would be a reasonable choice since crizotinib has limited penetration of blood-brain barrier.⁸¹

ROS1 REARRANGEMENTS

CASE PRESENTATION 3

A 66-year-old Chinese woman who is a non-smoker with a past medical history of hypertension and hypothyroidism presents to the emergency department for worsening lower back pain. Initial workup includes x-ray of the lumbar spine followed by MRI with contrast, which shows a soft tissue mass at L3-4 without cord compression. CT of the chest, abdomen, and pelvis with contrast shows a 7-cm right hilar mass, bilateral small lung nodules, mediastinal lymphadenopathy, and multiple lytic lesions in ribs, lumbar spine, and pelvis. MRI-brain with and without contrast is negative for malignancy. She undergoes endo-bronchial ultrasound and biopsy of the right hilar mass, which shows poorly differentiated adenocarcinoma. While waiting for the result of the molecular analysis, the patient undergoes palliative radiation therapy to L2-5 with good pain relief. She is discharged from the hospital and presents to your clinic for follow up. Molecular analysis now reveals ROS1 rearrangement with CD74-ROS1 fusion.

• What treatment plan should be put in place for this patient?

FIRST-LINE THERAPY FOR ROS1 REARRANGEMENTS

Approximately 2.4% of lung adenocarcinomas harbor ROS1 rearrangements.⁸² This distinct genetic alteration occurs more frequently in NSCLC patients who are younger, female, and never-smokers, and who have adenocarcinomas.⁸ It has been shown that ROS1 rearrangements rarely overlap with other genetic alterations including KRAS mutations, EGFR mutations, and ALK rearrangements.⁸³ As a receptor tyrosine kinase, ROS1 is similar to ALK and insulin receptor family members.⁸⁴ Crizotinib, which targets ALK, ROS1, and c-MET, was approved by the FDA on March 11, 2016, for the treatment of metastatic ROS1-rearranged NSCLC.⁸⁵ The approval was based on a phase 2 expansion cohort of the original phase 1 study. Among 50 US patients enrolled in this expansion cohort, 3 had complete responses and 33 had partial responses with ORR of 72% (95% CI 58% to 84%). Median PFS was 19.2 months (95% CI 14.4 months to NR) and median duration of response (DOR) was 17.6 months (95% CI 14.5 months to NR).⁸⁶ During longer follow-up, independent radiology review confirmed high ORR of 66% and median DOR of 18.3 months.⁸⁵

Interestingly, no companion diagnostic assay has been approved for the detection of ROS1 rearrangements with the approval of crizotinib. In the United States, break apart FISH is the most common detection method. In fact, in the above mentioned phase 2 study, ROS1 rearrangements were detected in 49 out of 50 patients by this method.⁸⁶ FISH can be technically challenging when dealing with high volume and multiple targets. Reverse transcriptase-PCR is another detection method, but it requires knowledge of the fusion partners. To date, at least 14 ROS1 fusion partners have been reported, with CD74 being the most common.⁸⁷ NGS with appropriate design and validation can also be used to detect ROS1 rearrangements.

For the case patient, the recommendation would be to start her on crizotinib at 250 mg twice daily. Monitoring for vision disturbance, gastrointestinal complaints, and edema is warranted. Because the estimated onset of response is around 7.9 weeks,⁸⁶ plans should be made to repeat her scans in approximately 2 months.

BRAF V600E MUTATIONS

CASE PRESENTATION 4

A 71-year-old Caucasian man with a past medical history of hypertension, dyslipidemia, and ischemic cerebrovascular accident without residual deficits was diagnosed with stage IV adenocarcinoma of the lung about 8 months ago. He has a 40 pack-year smoking history and quit smoking when he was diagnosed with lung cancer. His disease burden involved a large mediastinal mass, scattered pleural nodules, multiple lymphadenopathy, and several soft tissue masses. His outside oncologist started him on chemotherapy containing carboplatin and pemetrexed for 6 cycles followed by maintenance pemetrexed. The most recent restaging scans show disease progression with enlarging soft tissue masses and several new lytic bone lesions. MRI-brain with and without contrast shows 2 subcentimeter enhancing lesions. He transferred care to you approximately 4 weeks ago. You ordered a repeat biopsy of 1 of the enlarging soft tissue masses. Molecular analysis revealed BRAF V600E mutation. In the interim, he underwent stereotactic radiosurgery for the 2 brain lesions without any complications. The patient is now in your clinic for follow up.

• What would be your recommended systemic treatment?

TARGETED THERAPIES FOR BRAF V600E MUTATION

BRAF mutations were first recognized as activating mutations in advanced melanomas, with BRAF V600E, resulting from the substitution of glutamic acid for valine at amino acid 600, being the most common. BRAF plays an important role in the mitogen-activated protein kinase (MAPK) signaling pathway. Briefly, the activation of MAPK pathway occurs upon ligand binding of receptor tyrosine kinases, which then involves RAS/BRAF/MEK/ERK in a stepwise manner, ultimately leading to cell survival. BRAF mutations have been increasingly recognized also as driver mutations in NSCLC.^9–12 They can be detected by PCR or NGS method. The characteristics of NSCLC patients harboring BRAF mutations have been described by various groups.^9–12 For instance, 1 case series showed that the incidence was 2.2% among patients with advanced lung adenocarcinoma; 50% of mutations were V600E, while G469A and D594G accounted for the remaining 39% and 11% of patients, respectively. All patients were either current or former smokers. The median OS of patients with BRAF mutations in this case series was NR, while it was 37 months for patients with EGFR mutations (P = 0.73) and NR for patients with ALK rearrangements (P = 0.64).⁹

For patients with BRAF V600E–mutant NSCLC who have progressed on platinum-based chemotherapy, the combination of dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor) may represent a new treatment paradigm. This was illustrated in a phase 2, nonrandomized, open-label study. A total of 57 patients were enrolled and 36 patients (63.2% [95% CI 49.3% to 75.6%]) achieved an overall response by investigator assessment, the trial’s primary end point. Disease control rate was 78.9% (95% CI 66.1% to 88.6%), with 4% complete response, 60% partial response, and 16% stable disease. PFS was 9.7 months (95% CI [6.9 to 19.6 months]). The safety profile was comparable to what had been observed in patients with melanoma treated with this regimen. More specifically, 56% of patients on this trial reported serious AEs, including pyrexia (16%), anemia (5%), confusional state (4%), decreased appetite (4%), hemoptysis (4%), hypercalcemia (4%), nausea (4%), and cutaneous squamous cell carcinoma (4%). In addition, neutropenia (9%) and hyponatremia (7%) were the most common grade 3-4 AEs.¹⁶

The case patient has experienced disease progression after 1 line of platinum-based chemotherapy, so the combination of dabrafenib and trametinib would be a robust systemic treatment option. dabrafenib as a single agent has also been studied in BRAF V600E–mutant NSCLC in a phase 2 trial. The overall response by investigator assessment among 84 patients was 33% (95% CI 23% to 45%).¹⁴ Vemurafenib, another oral BRAF TKI, has demonstrated efficacy for NSCLC patients harboring BRAF V600E mutation. In the cohort of 20 patients with NSCLC, the response rate was 42% (95% CI 20% to 67%) and median PFS was 7.3 months (95% CI 3.5 to 10.8 months).¹³ Patients with non-V600E mutations have shown variable responses to targeted therapies. MEK TKIs may be considered in this setting; however, the details of this discussion are beyond the scope of this review.

CONCLUSION

The management of advanced NSCLC with driver mutations has seen revolutionary changes over the past decade. Tremendous research has been done in order to first understand the molecular pathogenesis of NSCLC and then discover driver mutations that would lead to development of targeted therapies with clinically significant efficacy as well as tolerability. More recently, increasing efforts have focused on how to conquer acquired resistance in patients with disease progression after first-line TKIs. The field of EGFR-mutant NSCLC has set a successful example, but the work is nowhere near finished. The goals are to search for more driver mutations and to design agents that could potentially block cell survival signals once and for all.

INTRODUCTION

The incidence of cutaneous melanoma has increased over the past 2 decades, with SEER estimates indicating that the number of new cases of melanoma diagnosed annually rose from 38,300 in 1996 to 76,000 in 2016.¹ Among persons younger than 50 years, the incidence is higher in females, and younger women (aged 15–39 years) are especially vulnerable.² Among persons older than 50, melanoma incidence in men is nearly twice that of women, in whom melanomas are often thicker and often associated with worse outcomes.^1,2 Approximately 85% of melanomas are diagnosed at early stages when surgery is curative, but the lifetime probability of developing invasive disease is 3% in men and 2% in women.

Prior to the advent of effective immunotherapies and targeted therapies, melanoma was often managed with chemotherapy, which had dismal response rates and commensurately poor outcomes. Advances in the understanding of the molecular etiopathogenesis and immune escape responses of cutaneous metastatic melanoma have transformed therapeutic approaches. Specifically, improved understanding of the genetic mutations driving melanoma tumorigenesis coupled with insights into mechanisms of tumor-mediated immune evasion resulted in development of inhibitors of mitogen-activated protein kinases (MAPK; BRAF and MEK) along with inhibitors of negative regulatory immune checkpoints (cytotoxic T lymphocyte–associated antigen 4 [CTLA-4] and programmed cell death-1 [PD-1]). In this review, we discuss the role of immune therapy, targeted therapy, and combinations of these in the treatment of metastatic cutaneous melanoma. We limit the immuno-therapy discussion to approved CTLA-4/PD-1 inhibitors and the targeted therapy discussion to approved BRAF/NRAS/MEK inhibitors and do not discuss non-checkpoint immunotherapies including cytokines (HD IL-2), vaccines, or adoptive T-cell approaches. Interested readers are directed to other excellent works covering these important topics.^26–29

DEVELOPMENT OF TARGETED AND NOVEL IMMUNE THERAPIES

For many years the degree of ultraviolet (UV) light exposure was considered the sole major risk factor for melanoma oncogenesis, even though its mechanism was largely unknown.³ However, clinical observations regarding the occurrence of melanoma on less exposed areas (trunk and limbs) in individuals with intermittent sun exposure led to the proposition that melanomas that arose in younger patients with intermittent sun exposure were distinct from melanomas that arose in older patients in association with markers of chronic sun exposure—the “divergent pathway” hypothesis.³ Critical to this understanding were whole-exome sequencing data from multiple groups, including The Cancer Genome Atlas, that identified patterns of mutations in oncogenic drivers that were distinct in patients with and without chronically sun-damaged (CSD) skin.^4–7 It is now clear that based on its association with CSD skin, melanoma can be subclassified into CSD or non-CSD melanoma. CSD and non-CSD melanoma have distinct clinico-pathological characteristics and are associated with different driver mutations. CSD melanomas typically arise in older patients on sun-exposed areas (head/neck, dorsal surfaces of distal extremities) and are associated with particular driver mutations (BRAF non-V600E, NRAS, NF1, or KIT) and genetic signatures of UV-induced DNA damage (G > T [UVA] or C > T [UVB]) transitions. Conversely, non-CSD melanomas typically arise in younger (< 55 years) patients on intermittently sun-exposed areas (trunk, proximal extremities) and are associated with BRAF V600E/K driver mutations and often lack genetic signatures of UV mutagenesis.

Identification of driver mutations in components of the MAPK pathway, including BRAF and NRAS, facilitated the development of targeted inhibitors. The BRAF inhibitors vemurafenib and dabrafenib have been shown in pivotal phase 3 studies to significantly improve overall and progression-free survival in patients with metastatic melanoma compared with chemotherapy and garnered regulatory approval (vemurafenib, BRIM-3;^8,9 dabrafenib, BREAK-3¹⁰). Concomitant MEK and BRAF inhibition extends the duration of benefit by preventing downstream kinase activation in the MAPK pathway. Notably, concomitant MEK inhibition alters the side-effect profile of BRAF inhibitors, with reduced incidence of keratoacanthomas and cutaneous squamous cell carcinomas that are attributable to on-target, off-tumor effects of BRAF inhibitors. Combined BRAF and MEK inhibition (vemurafenib/cobimetinib and dabrafenib/trametinib) further improved overall and progression-free survival compared to single-agent BRAF inhibition in phase 3 studies (COMBI-d,¹¹ COMBI-v,¹² and coBRIM¹³). Although often deep, the responses seen with the use of targeted kinase inhibitors are not often durable, with the vast majority of patients progressing after 12 to 15 months of therapy.In parallel, work primarily done in murine models of chronic viral infection uncovered the role played by co-inhibitory or co-excitatory immune checkpoints in mediating T-cell immune responses. These efforts clarified that tumor-mediated immune suppression primarily occurs through enhancement of inhibitory signals via the negative T-cell immune checkpoints CTLA-4 or PD-1.^14,15 Blockade of negative T-cell immune checkpoints resulted in activation of the adaptive immune system, resulting in durable anti-tumor responses as demonstrated in studies of the CTLA-4 inhibitor ipilimumab (CA184-020¹⁶ and CA184-024¹⁷) and the PD-1 inhibitors nivolumab (CA209-003,¹⁸ CheckMate 037,¹⁹ and CheckMate 066²⁰) and pembrolizumab (KEYNOTE-001²¹ and KEYNOTE-006²²). Compared to the deep but short-lived responses seen with targeted kinase inhibitors, patients treated with CTLA-4 or PD-1 immune checkpoint blockade often developed durable responses that persisted even after completion of therapy. Combined CTLA-4 and PD-1 blockade results in greater magnitude of response with proportionately increased toxicity.^23–25

IMMUNOTHERAPY

CTLA-4 AND PD-1 IMMUNE CHECKPOINT INHIBITORS

The novel success of immunotherapy in recent decades is largely attributable to improved understanding of adaptive immune physiology, specifically T-cell activation and regulation. T-cell activation requires 2 independent signaling events: it is initiated upon recognition of the antigen-MHC class II-receptor complex on antigen-presenting cells (APC), and requires a secondary co-stimulatory interaction of CD80/CD86 (B7.1/B7.2) on APCs and CD28 molecule on T-cells; without this second event, T-cells enter an anergic state.^30–32 Upon successful signaling and co-stimulation, newly activated T-cells upregulate CTLA-4, which can bind to B7 molecules with a nearly 100-fold greater affinity than CD28.^33,34 Unlike CD28, CTLA-4 engagement negatively regulates T-cell activation. The opposing signals produced by CD28 and CTLA-4 are integrated by the T-cell to determine eventual response to activation, and provide a means by which T-cell activation is homeostatically regulated to prevent exaggerated physiologic immune responses.³⁵ It was hypothesized that CTLA-4 blockade would permit T-cell activation, which is thwarted in the tumor microenvironment by tumor-mediated CTLA-4 engagement, thereby unleashing an anti-tumor immune response.³⁶

PD-1 is a member of the CD28 and CTLA-4 immunoglobulin super family and, similar to CTLA-4, binds activated T-cells. PD-1 has 2 ligands on activated T-cells: PD-L1 and PD-L2.³⁷ PD-L1 is constitutively expressed by a variety of immune and non-immune cells, particularly in inflammatory environments including tumor microenvironments, in response to the release of inflammatory cytokines such as interferon (IFN)-γ.^37,38 Conversely, PD-L2 is only minimally expressed constitutively, although its expression on immune and non-immune cells can be induced by similar cues from inflammatory microenvironments. PD-L1 and PD-L2 cross-compete for binding to PD-1, with PD-L2 exhibiting 2- to 6-fold greater relative affinity than PD-L1.³⁹ PD-L1/PD-1 binding results in phosphorylation of 2 tyrosinases in the intracellular portion of PD-1, which contains immunoreceptor tyrosine-based inhibitory motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM). PD-1 ITSM subsequently recruits either of 2 SH2-domain–containing protein tyrosine phosphatases: SHP-1 and SHP-2. SHP-2 signaling suppresses PI3K/Akt activation, down-regulates Bcl-xL, and suppresses expression of multiple transcription factors that mediate T-cell effector function including GATA-3, Eomes, and T-bet.^40–42 The net effect of PD-L1/PD-1 engagement is to suppress T-cell proliferation, cytokine production, cytolytic function, and survival. Unlike CTLA-4, which primarily affects the priming phase of naive T-cell activation, PD-1 chiefly regulates the effector phase of T-cell function. Furthermore, because PD-L1/PD-L2 expression is limited to inflammatory microenvironments, the effects of PD-1 are less generalized than those of CTLA-4.

SINGLE AGENT ACTIVITY OF CTLA-4 AND PD-1 INHIBITORS

Ipilimumab (MDX-010) is a human IgG1 monoclonal antibody shown to inhibit CTLA-4.⁴³ Early studies tested different formulations (transfectoma-derived and hybridoma-derived), doses, and schedules of ipilimumab primarily in patients with advanced refractory melanoma.^44–46 Although responses were infrequent, responding patients experienced durable remissions at 1- and 2-year time points. Notably, in a foreshadowing of changes to response criteria used to evaluate these agents, several treated patients who initially had radiographically stable disease upon completion of therapy subsequently experienced a gradual decline in tumor burden.

Ipilimumab was subsequently evaluated in 2 phase 3 trials. The first study (MDX010-020/CA184-020), which involved 676 HLA-A*0201–positive patients with advanced melanoma, compared ipilimumab 3 mg/kg every 3 weeks for 4 doses either singly or in combination with gp100 vaccine with a gp100-only control arm.¹⁶ Ipilimumab administration resulted in objective responses in 11% of patients and improved progression-free and overall survival compared to gp100 alone. Of note, ipilimumab monotherapy was superior to ipilimumab/gp100 combination, possibly related to timing of vaccine in relation to ipilimumab. A confirmatory study (CA184-024) compared a higher dose of ipilimumab (10 mg/kg) in combination with dacarbazine to dacarbazine monotherapy in previously untreated melanoma and was positive.¹⁷ Given the lack of augmented efficacy with the higher (10 mg/kg) dose, ipilimumab received regulatory approval in 2011 for the treatment of melanoma at the lower dose: 3 mg/kg administered every 3 weeks for 4 doses (Table 1). Survival data was strikingly similar to patterns observed in prior phase 2 studies, with survival curves plateauing after 2 years at 23.5% to 28.5% of treated patients. Pooled survival data from prospective and retrospective studies of ipilimumab corroborate the plateau of 22% (26% treated; 20% untreated) reached at year 3 regardless of prior therapy or ipilimumab dose, underscoring the durability of long-term survival in ipilimumab-treated patients.⁴⁷ Ipilimumab administration resulted in an unusual spectrum of toxicities including diarrhea, rash, hepatitis, and hypophysitis (termed immune-related adverse events, or irAEs) in up to a third of patients.

Pembrolizumab and nivolumab are humanized IgG4 monoclonal antibodies that target the PD-1 receptor found on activated T cells, B cells, and myeloid cells. Pembrolizumab and nivolumab are engineered similarly: by immunizing transgenic mice with recombinant human PD-1-Fc protein and subsequently screening murine splenic cells fused with myeloma cells for hybridomas producing antibodies reactive to PD-1-Fc.^48,49 Unlike IgG1, the IgG4 moiety neither engages Fc receptors nor activates complement, avoiding cytotoxic effects of the antibody upon binding to the T cells that it is intended to activate. Both pembrolizumab and nivolumab bind PD-1 with high affinity and specificity, effectively inhibiting the interaction between PD-1 and ligands PD-L1 and PD-L2.

Nivolumab was first studied in a phase 1 study (CA209-003) of 296 patients with advanced cancers who received 1, 3, or 10 mg/kg administered every 2 weeks.¹⁸ Histologies tested included melanoma, non–small-cell lung cancer (NSCLC), renal-cell cancer (RCC), castration-resistant prostate cancer (CRPC), and colorectal cancer (CRC). Responses were seen in melanoma and RCC and unusually in NSCLC, including in both squamous and non-squamous tumors. Objective responses were noted in 41% of the 107 melanoma patients treated at 3 mg/kg. Survival was improved, with 1- and 2-year survival rates of 62% and 43% at extended follow up.⁵⁰

Subsequently, nivolumab was compared to chemotherapy in a pair of phase 3 studies involving both previously untreated (Checkmate 066) and ipilimumab/BRAF inhibitor–refractory (CheckMate 037) patients.^19,20 In both studies, nivolumab produced durable responses in 32% to 34% of patients and improved survival over chemotherapy. Compared to ipilimumab, the incidence of irAEs was much lower with nivolumab. The depth and magnitude of responses observed led to regulatory approval for nivolumab in both indications (untreated and ipilimumab/BRAF inhibitor–treated melanoma) in 2014. Data from both studies are summarized in Table 1.

Pembrolizumab was first evaluated in a phase 1 study of 30 patients with a variety of solid organ malignancies in which no dose-limiting toxicities were observed and no defined maximal tolerated dose was reached.⁵¹ Per protocol, maximal administered dose was 10 mg/kg every 2 weeks. Following startling responses including 2 complete responses of long duration, pembrolizumab was evaluated in a large phase 1 study (KEYNOTE-001) of 1260 patients that evaluated 3 doses (10 mg/kg every 2 weeks, 10 mg/kg every 3 weeks, and 2 mg/kg every 3 weeks) in separate melanoma and NSCLC substudies.²¹ Both ipilimumab-naïve and ipilimumab-treated patients were enrolled in the melanoma substudy. Objective responses were seen in 38% ofpatients across all 3 dosing schedules and were similar in both ipilimumab-naïve and ipilimumab-treated patients. Similar to nivolumab, most responders experienced durable remissions.

Pembrolizumab was subsequently compared to ipilimumab in untreated patients (KEYNOTE-006) in which patients were randomly assigned to receive either ipilimumab or pembrolizumab at 1 of 2 doses: 10 mg/kg every 2 weeks and pembrolizumab 10 mg/kg every 3 weeks.²² Response rates were greater with pembrolizumab than ipilimumab, with commensurately greater 1-year survival rates. Rates of treatment-related adverse events requiring discontinuation of study drug were much lower with pembrolizumab than ipilimumab. This trial was instrumental in proving the superior profile of pembrolizumab over ipilimumab. The US Food and Drug Administration (FDA) granted pembrolizumab accelerated approval for second-line treatment of melanoma in 2014, and updated this to include a first-line indication in 2015 (Table 1).

EFFICACY OF COMBINED CTLA-4 AND PD-1 INHIBITION

Preclinical studies demonstrated that PD-1 blockade was more effective than CTLA-4 blockade and combination PD-1/CTLA-4 blockade was synergistic, with complete rejection of tumors in approximately half of the treated animals.¹⁴ This hypothesis was evaluated in a phase 1 study that explored both concurrent and sequential combinations of ipilimumab and nivolumab along with increasing doses of both agents in PD-1/CTLA-4–naïve advanced melanoma.²³ Responses were greater in the concurrent arm (40%) than in the sequential arm (20%) across dose-levels with a small fraction of patients treated in the concurrent arm experiencing a profound reduction (80%) in tumor burden.

The superiority of ipilimumab/nivolumab combination to ipilimumab monotherapy was demonstrated in a randomized blinded phase 2 study (CheckMate 069).²⁴ Of the 4 different ipilimumab/nivolumab doses explored in the phase 1 study (3 mg/kg and 0.3 mg/kg, 3 mg/kg and 1 mg/kg, 1 mg/kg and 3 mg/kg, 3 mg/kg and 3 mg/kg), ipilimumab 3 mg/kg and nivolumab 1 mg/kg (followed by nivolumab 3 mg/kg) was compared to ipilimumab and nivolumab-matched placebo. Responses were significantly greater with dual PD-1/CTLA-4 blockade compared to CTLA-4 blockade alone (59% versus 11%). Concurrently, a 3-arm randomized phase 3 study compared the same dose of ipilimumab/nivolumab to ipilimumab and nivolumab in previously untreated advanced melanoma (CheckMate 067).²⁵ Similar to CheckMate 069, CheckMate 067 demonstrated that ipilimumab/nivolumab combination resulted in more profound responses (58%) than either ipilimumab (19%) or nivolumab (44%) alone. Toxicity, primarily diarrhea, fatigue, pruritus, and rash, was considerable in the combination arm (55% grade 3/4 adverse events) and resulted in treatment discontinuation in 30% of patients. The profound and durable responses observed led to accelerated approval of ipilimumab/nivolumab combination in 2015 (Table 1).

Efforts to improve the toxicity/benefit ratio of ipilimumab/nivolumab combination have centered around studying lower doses and/or extended dosing schedules of ipilimumab, including ipilimumab 1 mg/kg every 6 or 12 weeks with nivolumab dosed at 3 mg/kg every 2 weeks or 480 mg every 4 weeks. Promising data from a first-line study in NSCLC (CheckMate 012) support the evaluation of nivolumab in combination with lower-dosed ipilimumab (1 mg/kg every 6 or 12 weeks).⁵² This approach is being tested against platinum doublet chemotherapy in a confirmatory phase 3 study in NSCLC (CheckMate 227).

TARGETED THERAPY

MAPK KINASE PATHWAY IN MELANOMA TUMORIGENESIS

The MAPK pathway mediates cellular responses to growth signals. RAF kinases are central mediators in the MAPK pathway and exert their effect primarily through MEK phosphorylation and activation following dimerization (hetero- or homo-) of RAF molecules. As a result, RAF is integral to multiple cellular processes, including transcriptional regulation, cellular differentiation, and cell proliferation. MAPK pathway activation is a common event in many cancers, primarily due to activating mutations in BRAF or RAS. Alternatively, MAPK pathway activation can occur in the absence of activating mutations in BRAF or NRAS through down-regulation of MAPK pathway inhibitory proteins (RAF-1 inhibitory protein or SPRY-2), C-MET overexpression, or activating mutations in non-BRAF/NRAS kinases including CRAF, HRAS, and NRAS.^53,54

Somatic point mutations in BRAF are frequently observed (37%–50%) in malignant melanomas and at lower frequency in a range of human cancers including NSCLC, colorectal cancer, papillary thyroid cancer, ovarian cancer, glioma, and gastrointestinal stromal tumor.^6,55,56BRAF mutations in melanoma typically occur within the activation segment of the kinase domain (exon 15). Between 80% and 90% of activating mutations result in an amino acid substitution of glutamate (E) for valine (V) at position 600: V600E.^57,58 V600E mutations are true oncogenic drivers, resulting in increased kinase activity with demonstrable transformational capacity in vitro. BRAF mutations are usually mutually exclusive, with tumors typically containing no other driver mutations in NRAS, KIT, NF1, or other genes.

NRAS mutations are less common than BRAF mutations, having a reported frequency of 13% to 25% in melanoma.⁴NRAS mutations generally occur within the P-loop region of the G domain (exon 2), or less commonly in the switch II region of the G domain (exon 3). Most NRAS exon 2 mutations comprise amino acid substitutions at position 61 from glutamine (Q) to arginine (R; 35%), lysine (K; 34%) and less often to glutamate (E), leucine (L), or proline (P). Preclinical data suggest that NRAS mutations paradoxically stimulate the MAPK pathway and thus enhance tumor growth in vitro.^59,60 Several important phenotypic differences distinguish NRAS- from BRAF-mutated melanoma. NRAS-mutated tumors are typically associated with increasing age and CSD skin, while BRAF-mutated tumors arise in younger patients in non-CSD skin. A large population-based study suggested that NRAS-mutated melanomas were associated with mitoses and lower tumor infiltrating lymphocytes (TIL) grade, and arose in anatomic sites other than the head/neck, while BRAF-mutated tumors were associated with mitoses and superficial spreading histology.⁶¹ Although the lower TIL grade seen with NRAS-mutated melanomas suggests a more immunosuppressed microenvironment and argues for poorer responses to immune therapies, clinical studies comparing responses to immunotherapies in various categories of driver mutations provide conflicting results for the prognostic role of NRAS mutations in relation to immune checkpoint blockade and other immune therapies.^62–64

NF1 represents the third known driver in cutaneous melanoma, with mutations reported in 12% of cases.^6,7NF1 encodes neurofibromin, which has GTPase activity and regulates RAS proteins; NF1 loss results in increased RAS.⁶⁵ Unlike BRAF or NRAS, which are usually mutually exclusive, NF1 mutations in melanoma can occur singly or in combination with either BRAF or NRAS mutations. In these settings, NF1 mutations are associated with RAS activation, MEK-dependence, and resistance to RAF inhibition.⁶⁶

MAPK PATHWAY INHIBITION SINGLY AND IN COMBINATION

Although multiple MEK 1/2 inhibitors (AS703026, AZD8330/ARRY-704, AZD6244, CH5126766, CI-1040, GSK1120212, PD0325901, RDEA119, and XL518) and RAF inhibitors (ARQ 680, GDC-0879, GSK2118436, PLX4032, RAF265, sorafenib, XL281/BMS-908662) were developed, the initial evaluation of MAPK pathway inhibitors in advanced human cancers began with CI-1040. Preclinical data suggested that CI-1040 potently and selectively inhibited both MEK1 and MEK2, but phase 1 and 2 human trial results were disappointing, likely because these trials were not selectively enriched for NRAS/BRAF–mutated tumors or cancers in which these oncogenic mutations were most commonly detected, such as melanoma.^67,68 The subsequent evaluation of selumetinib (AZD6244/ARRY-142886) in a phase 2 study was also negative. Although investigators enrolled a presumably enriched population (cutaneous melanoma), the incidence of NRAS/BRAF–mutated tumors was not ascertained to determine this, but rather assumed, which led to a discrepancy between the assumed (prestudy) and observed (on-study) proportions of BRAF/NRAS mutations that was not accounted for in power calculations.^69,70 Lessons learned from these earlier misadventures informed the current paradigm of targeted therapy development: (1) identification of a highly specific and potent inhibitor through high-throughput screening; (2) establishment of maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) in unselected patients; (3) confirmation of RP2D in selected tumor types enriched for target of interest; and (4) confirmatory study against standard comparator to seek regulatory approval.

Vemurafenib and dabrafenib were evaluated in this tiered fashion in phase 1 dose-finding studies comprising unselected patients, followed by phase 2 studies in advanced BRAF V600E–mutated melanoma. Both were subsequently evaluated in randomized phase 3 trials (vemurafenib, BRIM-38; dabrafenib, BREAK-310) that compared them with dacarbazine (1000 mg/m² intravenously every 3 weeks) in the treatment of advanced BRAF V600E–mutated melanoma. Response kinetics for both agents were remarkably similar: single-agent BRAF inhibitors resulted in rapid (time to response 2–3 months), profound (approximately 50% objective responses) reductions in tumor burden that lasted 6 to 7 months. Adverse events common to both agents included rash, fatigue, and arthralgia, although clinically significant photosensitivity was more common with vemurafenib and clinically significant pyrexia was more common with dabrafenib. Class-specific adverse events included the development of cutaneous squamous-cell carcinomas and keratoacanthomas secondary to paradoxical activation of MAPK pathway signaling either through activating mutations in HRAS or mutations or amplifications in receptor tyrosine kinases upstream of BRAF, resulting in elevated levels of RAS–guanosine triphosphate complexes.⁷¹ Results of these studies resulted in regulatory approval of single-agent BRAF inhibitors for the treatment of BRAF V600E (and later V600K)–mutated melanoma (vemurafenib in 2011; dabrafenib in 2013). Details regarding trial populations, study interventions, efficacy, and adverse events are summarized in Table 2.

Responses to BRAF inhibitors are typically profound but temporary. Mechanisms of acquired resistance are diverse and include reactivation of MAPK pathway–dependent signaling (RAS activation or increased RAF expression), and development of MAPK pathway–independent signaling (COT overexpression; increased PI3K or AKT signaling) that permits bypass of inhibited BRAF signaling within the MAPK pathway.^72–76 These findings suggested that upfront inhibition of both MEK and mutant BRAF may produce more durable responses than BRAF inhibition alone. Three pivotal phase 3 studies established the superiority of combination BRAF and MEK inhibition over BRAF inhibition alone: COMBI-d11 (dabrafenib/trametinib versus dabrafenib/placebo), COMBI-v12 (dabrafenib/trametinib versus vemurafenib), and coBRIM13 (vemurafenib/cobimetinib versus vemurafenib/placebo). As expected, compared to BRAF inhibitor monotherapy, combination BRAF and MEK inhibition produced greater responses and improved progression-free and overall survival (Table 2). Interestingly, the rate of cutaneous squamous-cell carcinomas was much lower with combination therapy, reflecting the more profound degree of MAPK pathway inhibition achieved with combination BRAF and MEK inhibition. Based on these results, FDA approval was granted for both dabrafenib/trametinib and vemurafenib/cobimetinib combinations in 2015. Although the dabrafenib/trametinib combination was only approved in 2015, trametinib had independently gained FDA approval in 2013 for the treatment of BRAF V600E/K–mutated melanoma on the basis of the phase 3 METRIC study.⁷⁷

Encorafenib (LGX818) and binimetinib (MEK162, ARRY-162, ARRY-438162) are new BRAF and MEK inhibitors currently being evaluated in clinical trials. Encorafenib/binimetinib combination was first evaluated in a phase 3 study (COLUMBUS) that compared it with vemurafenib monotherapy in BRAF-mutant melanoma.⁷⁸ Unsurprisingly, encorafenib/binimetinib combination produced greater and more durable responses compared to vemurafenib monotherapy. The median progression-free survival of the encorafenib/binimetinib combination (14.9 months) was greater than vemurafenib monotherapy (7.3 months) in this study, and intriguingly greater than that seen with vemurafenib/cobimetinib (coBRIM 9.9 months) and dabrafenib/trametinib (COMBI-d 9.3 months; COMBI-v 11.4 months). Of note, although encorafenib has an IC50 midway between dabrafenib and vemurafenib in cell-free assays (0.8 nM dabrafenib, 4 nM encorafenib, and 31 nM vemurafenib), it has an extremely slower off-rate from BRAF V600E, which results in significantly greater target inhibition in cells following drug wash-out.⁷⁹ This may account for the significantly greater clinical benefit seen with encorafenib/binimetinib in clinical trials. Final study data are eagerly awaited. Regulatory approval has been sought, and is pending at this time.

Binimetinib has been compared to dacarbazine in a phase 3 study (NEMO) of patients with NRAS-mutant melanoma, most of whom had been previously treated with immunotherapy.⁸⁰ Response rates were low in both arms, although slightly greater with binimetinib than dacarbazine (15% versus 9%), commensurate with a modest improvement in progression-free survival. FDA approval has been sought and remains pending at this time.

KIT INHIBITION SINGLY AND IN COMBINATION

The KIT receptor protein tyrosine kinase is a transmembrane protein consisting of extracellular and intracellular domains. Activating KIT mutations occur in 2% to 8% of all melanoma patients and may be found in all melanoma subtypes but are commonest in acral melanomas (10%–20%) and mucosal melanomas (15%–20%). Activating KIT mutations primarily occur in exons 11 and 13, which code for the juxtamembrane and kinase domains, respectively.^5,81–83

Imatinib mesylate is a tyrosine kinase inhibitor of the 2-phenyl amino pyrimidine class that occupies the tyrosine kinase active site with resultant blocking of tyrosine kinase activity. Imatinib mesylate is known to block KIT and has been extensively studied in patients with gastrointestinal stromal tumors (GIST), 80% of whom harbor KIT mutations, in both the adjuvant and the metastatic settings. In melanoma, imatinib mesylate was studied in a Chinese open-label, phase 2 study of imatinib mesylate monotherapy in metastatic melanoma harboring KIT mutation or amplification; 25% of the study patients had mucosal disease and the rest had cutaneous disease, with acral involvement in 50% of all patients.⁸⁴ Overall response rate was 23%, while 51% of patients remained alive at 1 year with no differences in response rate and/or survival being noted between patients with either KIT mutations or amplifications. In a separate study of imatinib mesylate at 400 mg daily or 400 mg twice daily in Caucasian patients with KIT-mutated/amplified melanoma, similar response and survival rates were reported, although patients with KIT mutations did nonsignificantly better than those with KIT amplifications.⁸⁵

Other novel studies evaluating KIT inhibitors include KIT inhibition in combination with the VEGF inhibitor bevacizumab and a study of selective BCR-ABL kinase inhibitor nilotinib in imatinib-resistant melanoma. In the former phase 1/2 study, Flaherty and colleagues studied imatinib 800 mg daily and bevacizumab at 10 mg/kg every 2 weeks in 63 patients with advanced tumors, including 23 with metastatic melanoma. Although the combination was relatively nontoxic, no significant efficacy signal was seen and further accrual to the phase 2 portion was halted after the first stage was completed.⁸⁶ Nilotinib is a BCR-ABL1 tyrosine kinase inhibitor intelligently designed based on the structure of the ABL-imatinib complex that is 10 to 30 times more potent than imatinib in inhibiting BCR-ABL1 tyrosine kinase activity. Nilotinib is approved for the treatment of imatinib-resistant chronic myelogenous leukemia (CML), with reported efficacy in patients with central nervous system (CNS) involvement.^87,88 Nilotinib has been studied in a single study of KIT-mutated/amplified melanoma that included patients with imatinib-resistance and those with treated CNS disease. Nilotinib appeared to be active in imatinib-resistant melanoma, although no responses were seen in the CNS disease cohort.⁸⁹ Overall, the response rates observed with KIT inhibition in melanoma are much lower than those observed in CML and GIST.

CONCLUSION AND FUTURE DIRECTIONS

Prior to 2011, the only approved agents for the treatment of advanced melanoma were dacarbazine and high-dose interleukin-2. Since 2011, drug approvals in melanoma have proceeded at a frenetic pace unmatched in any other disease. The primary events underlying this are advances in our understanding of the gene mutation landscape driving melanoma tumorigenesis, accompanied by insights into the means by which tumors circumvent the induction of effective anti-tumor T-cell responses. These insights have resulted in the development of inhibitors targeting MAPK pathway kinases BRAF, MEK, and NRAS), KIT, and regulatory immune checkpoints (CTLA-4 and PD-1). Although BRAF/MEK inhibition results in profound reductions and even occasional complete responses in patients, these responses are typically short lived, rarely lasting more than 9 to 11 months; the encorafenib/binimetinib combination may improve that duration marginally. However, the signature therapeutic advance in melanoma of the past decade is immunotherapy, particularly the development of inhibitors of CTLA-4 and PD-1 immune checkpoints. With these agents, significant proportions of treated patients remain free of progression off-therapy (ipilimumab 23%; nivolumab 34%; pembrolizumab 35%; ipilimumab/nivolumab 64%), and some patients can be successfully re-induced after delayed progression. Separately, the high response rates observed with the use of KIT inhibitors in CML and GIST have not been observed in KIT mutated/amplified melanoma and development of agents in this space has been limited. The challenges ahead center around identifying predictive biomarkers and circumventing primary or acquired resistance, with the eventual goal of producing durable remissions in the majority of treated patients.

Our improved understanding of the mechanisms of acquired resistance to BRAF/MEK inhibitors suggests that anti-tumor activity may be achieved by targeting multiple pathways, possibly with combination regimens comprising other inhibitors and/or immunotherapy. Preclinical data supports the use of combination strategies targeting both ERK and PI3K/mTOR to circumvent acquired resistance.⁹⁰ Ongoing studies are evaluating combinations with biguanides (metformin: NCT02143050 and NCT01638676; phenformin: NCT03026517), HSP90 inhibitors (XL888: NCT02721459; AT13387: NCT02097225), and decitabine (NCT01876641).

One complexity affecting management of resistance in the targeted therapy landscape remains tumor heterogeneity, particularly intra- and intertumoral heterogeneity, which may explain the apparent contradiction between continued efficacy of BRAF inhibitors in BRAF-resistant tumors and preclinical data predicting slower progression of resistant tumors on cessation of BRAF inhibitors.^91–94 These data provide a rationale to investigate intermittent dosing regimens with BRAF/MEK inhibitors; several studies exploring this approach are ongoing (NCT01894672 and NCT02583516).

Given the specificity, adaptability, and memory response associated with immunotherapy, it is likely that these agents will be used to treat the majority of patients regardless of mutational status. Hence, identifying predictive biomarkers of response to immune checkpoint inhibitors is vital. The presence of CD8+ T-cell infiltrate and IFN-γ gene signature, which indicate an “inflamed” tumor microenvironment, are highly predictive of clinical benefit from PD-1 inhibitors.^95,96 However, not all PD-1 responders have “inflamed” tumor microenvironments, and not all patients with an “inflamed” tumor microenvironment respond to immune checkpoint inhibitors. The complexity of the immune system is reflected in the multiple non-redundant immunologic pathways, both positive and negative, with checkpoints and ligands that emerge dynamically in response to treatment. Given the dynamic nature of the immune response, it is unlikely that any single immunologic biomarker identified pre-treatment will be completely predictive. Rather, the complexity of the biomarker approach must match the complexity of the immune response elicited, and will likely incorporate multifarious elements including CD8+ T-cell infiltrate, IFN-γ gene signature, and additional elements including microbiome, genetic polymorphisms, and tumor mutation load. The goal is to use multiple markers to guide development of combinations and then, depending on initial response, to examine tumors for alterations to guide decisions about additional treatment(s) to improve responses, with the eventual goal being durable clinical responses for all patients.

INTRODUCTION

The incidence of cutaneous melanoma has increased over the past 2 decades, with SEER estimates indicating that the number of new cases of melanoma diagnosed annually rose from 38,300 in 1996 to 76,000 in 2016.¹ Among persons younger than 50 years, the incidence is higher in females, and younger women (aged 15–39 years) are especially vulnerable.² Among persons older than 50, melanoma incidence in men is nearly twice that of women, in whom melanomas are often thicker and often associated with worse outcomes.^1,2 Approximately 85% of melanomas are diagnosed at early stages when surgery is curative, but the lifetime probability of developing invasive disease is 3% in men and 2% in women.

Prior to the advent of effective immunotherapies and targeted therapies, melanoma was often managed with chemotherapy, which had dismal response rates and commensurately poor outcomes. Advances in the understanding of the molecular etiopathogenesis and immune escape responses of cutaneous metastatic melanoma have transformed therapeutic approaches. Specifically, improved understanding of the genetic mutations driving melanoma tumorigenesis coupled with insights into mechanisms of tumor-mediated immune evasion resulted in development of inhibitors of mitogen-activated protein kinases (MAPK; BRAF and MEK) along with inhibitors of negative regulatory immune checkpoints (cytotoxic T lymphocyte–associated antigen 4 [CTLA-4] and programmed cell death-1 [PD-1]). In this review, we discuss the role of immune therapy, targeted therapy, and combinations of these in the treatment of metastatic cutaneous melanoma. We limit the immuno-therapy discussion to approved CTLA-4/PD-1 inhibitors and the targeted therapy discussion to approved BRAF/NRAS/MEK inhibitors and do not discuss non-checkpoint immunotherapies including cytokines (HD IL-2), vaccines, or adoptive T-cell approaches. Interested readers are directed to other excellent works covering these important topics.^26–29

DEVELOPMENT OF TARGETED AND NOVEL IMMUNE THERAPIES

For many years the degree of ultraviolet (UV) light exposure was considered the sole major risk factor for melanoma oncogenesis, even though its mechanism was largely unknown.³ However, clinical observations regarding the occurrence of melanoma on less exposed areas (trunk and limbs) in individuals with intermittent sun exposure led to the proposition that melanomas that arose in younger patients with intermittent sun exposure were distinct from melanomas that arose in older patients in association with markers of chronic sun exposure—the “divergent pathway” hypothesis.³ Critical to this understanding were whole-exome sequencing data from multiple groups, including The Cancer Genome Atlas, that identified patterns of mutations in oncogenic drivers that were distinct in patients with and without chronically sun-damaged (CSD) skin.^4–7 It is now clear that based on its association with CSD skin, melanoma can be subclassified into CSD or non-CSD melanoma. CSD and non-CSD melanoma have distinct clinico-pathological characteristics and are associated with different driver mutations. CSD melanomas typically arise in older patients on sun-exposed areas (head/neck, dorsal surfaces of distal extremities) and are associated with particular driver mutations (BRAF non-V600E, NRAS, NF1, or KIT) and genetic signatures of UV-induced DNA damage (G > T [UVA] or C > T [UVB]) transitions. Conversely, non-CSD melanomas typically arise in younger (< 55 years) patients on intermittently sun-exposed areas (trunk, proximal extremities) and are associated with BRAF V600E/K driver mutations and often lack genetic signatures of UV mutagenesis.

Identification of driver mutations in components of the MAPK pathway, including BRAF and NRAS, facilitated the development of targeted inhibitors. The BRAF inhibitors vemurafenib and dabrafenib have been shown in pivotal phase 3 studies to significantly improve overall and progression-free survival in patients with metastatic melanoma compared with chemotherapy and garnered regulatory approval (vemurafenib, BRIM-3;^8,9 dabrafenib, BREAK-3¹⁰). Concomitant MEK and BRAF inhibition extends the duration of benefit by preventing downstream kinase activation in the MAPK pathway. Notably, concomitant MEK inhibition alters the side-effect profile of BRAF inhibitors, with reduced incidence of keratoacanthomas and cutaneous squamous cell carcinomas that are attributable to on-target, off-tumor effects of BRAF inhibitors. Combined BRAF and MEK inhibition (vemurafenib/cobimetinib and dabrafenib/trametinib) further improved overall and progression-free survival compared to single-agent BRAF inhibition in phase 3 studies (COMBI-d,¹¹ COMBI-v,¹² and coBRIM¹³). Although often deep, the responses seen with the use of targeted kinase inhibitors are not often durable, with the vast majority of patients progressing after 12 to 15 months of therapy.In parallel, work primarily done in murine models of chronic viral infection uncovered the role played by co-inhibitory or co-excitatory immune checkpoints in mediating T-cell immune responses. These efforts clarified that tumor-mediated immune suppression primarily occurs through enhancement of inhibitory signals via the negative T-cell immune checkpoints CTLA-4 or PD-1.^14,15 Blockade of negative T-cell immune checkpoints resulted in activation of the adaptive immune system, resulting in durable anti-tumor responses as demonstrated in studies of the CTLA-4 inhibitor ipilimumab (CA184-020¹⁶ and CA184-024¹⁷) and the PD-1 inhibitors nivolumab (CA209-003,¹⁸ CheckMate 037,¹⁹ and CheckMate 066²⁰) and pembrolizumab (KEYNOTE-001²¹ and KEYNOTE-006²²). Compared to the deep but short-lived responses seen with targeted kinase inhibitors, patients treated with CTLA-4 or PD-1 immune checkpoint blockade often developed durable responses that persisted even after completion of therapy. Combined CTLA-4 and PD-1 blockade results in greater magnitude of response with proportionately increased toxicity.^23–25

IMMUNOTHERAPY

CTLA-4 AND PD-1 IMMUNE CHECKPOINT INHIBITORS

The novel success of immunotherapy in recent decades is largely attributable to improved understanding of adaptive immune physiology, specifically T-cell activation and regulation. T-cell activation requires 2 independent signaling events: it is initiated upon recognition of the antigen-MHC class II-receptor complex on antigen-presenting cells (APC), and requires a secondary co-stimulatory interaction of CD80/CD86 (B7.1/B7.2) on APCs and CD28 molecule on T-cells; without this second event, T-cells enter an anergic state.^30–32 Upon successful signaling and co-stimulation, newly activated T-cells upregulate CTLA-4, which can bind to B7 molecules with a nearly 100-fold greater affinity than CD28.^33,34 Unlike CD28, CTLA-4 engagement negatively regulates T-cell activation. The opposing signals produced by CD28 and CTLA-4 are integrated by the T-cell to determine eventual response to activation, and provide a means by which T-cell activation is homeostatically regulated to prevent exaggerated physiologic immune responses.³⁵ It was hypothesized that CTLA-4 blockade would permit T-cell activation, which is thwarted in the tumor microenvironment by tumor-mediated CTLA-4 engagement, thereby unleashing an anti-tumor immune response.³⁶

PD-1 is a member of the CD28 and CTLA-4 immunoglobulin super family and, similar to CTLA-4, binds activated T-cells. PD-1 has 2 ligands on activated T-cells: PD-L1 and PD-L2.³⁷ PD-L1 is constitutively expressed by a variety of immune and non-immune cells, particularly in inflammatory environments including tumor microenvironments, in response to the release of inflammatory cytokines such as interferon (IFN)-γ.^37,38 Conversely, PD-L2 is only minimally expressed constitutively, although its expression on immune and non-immune cells can be induced by similar cues from inflammatory microenvironments. PD-L1 and PD-L2 cross-compete for binding to PD-1, with PD-L2 exhibiting 2- to 6-fold greater relative affinity than PD-L1.³⁹ PD-L1/PD-1 binding results in phosphorylation of 2 tyrosinases in the intracellular portion of PD-1, which contains immunoreceptor tyrosine-based inhibitory motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM). PD-1 ITSM subsequently recruits either of 2 SH2-domain–containing protein tyrosine phosphatases: SHP-1 and SHP-2. SHP-2 signaling suppresses PI3K/Akt activation, down-regulates Bcl-xL, and suppresses expression of multiple transcription factors that mediate T-cell effector function including GATA-3, Eomes, and T-bet.^40–42 The net effect of PD-L1/PD-1 engagement is to suppress T-cell proliferation, cytokine production, cytolytic function, and survival. Unlike CTLA-4, which primarily affects the priming phase of naive T-cell activation, PD-1 chiefly regulates the effector phase of T-cell function. Furthermore, because PD-L1/PD-L2 expression is limited to inflammatory microenvironments, the effects of PD-1 are less generalized than those of CTLA-4.

SINGLE AGENT ACTIVITY OF CTLA-4 AND PD-1 INHIBITORS

Ipilimumab (MDX-010) is a human IgG1 monoclonal antibody shown to inhibit CTLA-4.⁴³ Early studies tested different formulations (transfectoma-derived and hybridoma-derived), doses, and schedules of ipilimumab primarily in patients with advanced refractory melanoma.^44–46 Although responses were infrequent, responding patients experienced durable remissions at 1- and 2-year time points. Notably, in a foreshadowing of changes to response criteria used to evaluate these agents, several treated patients who initially had radiographically stable disease upon completion of therapy subsequently experienced a gradual decline in tumor burden.

Ipilimumab was subsequently evaluated in 2 phase 3 trials. The first study (MDX010-020/CA184-020), which involved 676 HLA-A*0201–positive patients with advanced melanoma, compared ipilimumab 3 mg/kg every 3 weeks for 4 doses either singly or in combination with gp100 vaccine with a gp100-only control arm.¹⁶ Ipilimumab administration resulted in objective responses in 11% of patients and improved progression-free and overall survival compared to gp100 alone. Of note, ipilimumab monotherapy was superior to ipilimumab/gp100 combination, possibly related to timing of vaccine in relation to ipilimumab. A confirmatory study (CA184-024) compared a higher dose of ipilimumab (10 mg/kg) in combination with dacarbazine to dacarbazine monotherapy in previously untreated melanoma and was positive.¹⁷ Given the lack of augmented efficacy with the higher (10 mg/kg) dose, ipilimumab received regulatory approval in 2011 for the treatment of melanoma at the lower dose: 3 mg/kg administered every 3 weeks for 4 doses (Table 1). Survival data was strikingly similar to patterns observed in prior phase 2 studies, with survival curves plateauing after 2 years at 23.5% to 28.5% of treated patients. Pooled survival data from prospective and retrospective studies of ipilimumab corroborate the plateau of 22% (26% treated; 20% untreated) reached at year 3 regardless of prior therapy or ipilimumab dose, underscoring the durability of long-term survival in ipilimumab-treated patients.⁴⁷ Ipilimumab administration resulted in an unusual spectrum of toxicities including diarrhea, rash, hepatitis, and hypophysitis (termed immune-related adverse events, or irAEs) in up to a third of patients.

Pembrolizumab and nivolumab are humanized IgG4 monoclonal antibodies that target the PD-1 receptor found on activated T cells, B cells, and myeloid cells. Pembrolizumab and nivolumab are engineered similarly: by immunizing transgenic mice with recombinant human PD-1-Fc protein and subsequently screening murine splenic cells fused with myeloma cells for hybridomas producing antibodies reactive to PD-1-Fc.^48,49 Unlike IgG1, the IgG4 moiety neither engages Fc receptors nor activates complement, avoiding cytotoxic effects of the antibody upon binding to the T cells that it is intended to activate. Both pembrolizumab and nivolumab bind PD-1 with high affinity and specificity, effectively inhibiting the interaction between PD-1 and ligands PD-L1 and PD-L2.

Nivolumab was first studied in a phase 1 study (CA209-003) of 296 patients with advanced cancers who received 1, 3, or 10 mg/kg administered every 2 weeks.¹⁸ Histologies tested included melanoma, non–small-cell lung cancer (NSCLC), renal-cell cancer (RCC), castration-resistant prostate cancer (CRPC), and colorectal cancer (CRC). Responses were seen in melanoma and RCC and unusually in NSCLC, including in both squamous and non-squamous tumors. Objective responses were noted in 41% of the 107 melanoma patients treated at 3 mg/kg. Survival was improved, with 1- and 2-year survival rates of 62% and 43% at extended follow up.⁵⁰

Subsequently, nivolumab was compared to chemotherapy in a pair of phase 3 studies involving both previously untreated (Checkmate 066) and ipilimumab/BRAF inhibitor–refractory (CheckMate 037) patients.^19,20 In both studies, nivolumab produced durable responses in 32% to 34% of patients and improved survival over chemotherapy. Compared to ipilimumab, the incidence of irAEs was much lower with nivolumab. The depth and magnitude of responses observed led to regulatory approval for nivolumab in both indications (untreated and ipilimumab/BRAF inhibitor–treated melanoma) in 2014. Data from both studies are summarized in Table 1.

Pembrolizumab was first evaluated in a phase 1 study of 30 patients with a variety of solid organ malignancies in which no dose-limiting toxicities were observed and no defined maximal tolerated dose was reached.⁵¹ Per protocol, maximal administered dose was 10 mg/kg every 2 weeks. Following startling responses including 2 complete responses of long duration, pembrolizumab was evaluated in a large phase 1 study (KEYNOTE-001) of 1260 patients that evaluated 3 doses (10 mg/kg every 2 weeks, 10 mg/kg every 3 weeks, and 2 mg/kg every 3 weeks) in separate melanoma and NSCLC substudies.²¹ Both ipilimumab-naïve and ipilimumab-treated patients were enrolled in the melanoma substudy. Objective responses were seen in 38% ofpatients across all 3 dosing schedules and were similar in both ipilimumab-naïve and ipilimumab-treated patients. Similar to nivolumab, most responders experienced durable remissions.

Pembrolizumab was subsequently compared to ipilimumab in untreated patients (KEYNOTE-006) in which patients were randomly assigned to receive either ipilimumab or pembrolizumab at 1 of 2 doses: 10 mg/kg every 2 weeks and pembrolizumab 10 mg/kg every 3 weeks.²² Response rates were greater with pembrolizumab than ipilimumab, with commensurately greater 1-year survival rates. Rates of treatment-related adverse events requiring discontinuation of study drug were much lower with pembrolizumab than ipilimumab. This trial was instrumental in proving the superior profile of pembrolizumab over ipilimumab. The US Food and Drug Administration (FDA) granted pembrolizumab accelerated approval for second-line treatment of melanoma in 2014, and updated this to include a first-line indication in 2015 (Table 1).

EFFICACY OF COMBINED CTLA-4 AND PD-1 INHIBITION

Preclinical studies demonstrated that PD-1 blockade was more effective than CTLA-4 blockade and combination PD-1/CTLA-4 blockade was synergistic, with complete rejection of tumors in approximately half of the treated animals.¹⁴ This hypothesis was evaluated in a phase 1 study that explored both concurrent and sequential combinations of ipilimumab and nivolumab along with increasing doses of both agents in PD-1/CTLA-4–naïve advanced melanoma.²³ Responses were greater in the concurrent arm (40%) than in the sequential arm (20%) across dose-levels with a small fraction of patients treated in the concurrent arm experiencing a profound reduction (80%) in tumor burden.

The superiority of ipilimumab/nivolumab combination to ipilimumab monotherapy was demonstrated in a randomized blinded phase 2 study (CheckMate 069).²⁴ Of the 4 different ipilimumab/nivolumab doses explored in the phase 1 study (3 mg/kg and 0.3 mg/kg, 3 mg/kg and 1 mg/kg, 1 mg/kg and 3 mg/kg, 3 mg/kg and 3 mg/kg), ipilimumab 3 mg/kg and nivolumab 1 mg/kg (followed by nivolumab 3 mg/kg) was compared to ipilimumab and nivolumab-matched placebo. Responses were significantly greater with dual PD-1/CTLA-4 blockade compared to CTLA-4 blockade alone (59% versus 11%). Concurrently, a 3-arm randomized phase 3 study compared the same dose of ipilimumab/nivolumab to ipilimumab and nivolumab in previously untreated advanced melanoma (CheckMate 067).²⁵ Similar to CheckMate 069, CheckMate 067 demonstrated that ipilimumab/nivolumab combination resulted in more profound responses (58%) than either ipilimumab (19%) or nivolumab (44%) alone. Toxicity, primarily diarrhea, fatigue, pruritus, and rash, was considerable in the combination arm (55% grade 3/4 adverse events) and resulted in treatment discontinuation in 30% of patients. The profound and durable responses observed led to accelerated approval of ipilimumab/nivolumab combination in 2015 (Table 1).

Efforts to improve the toxicity/benefit ratio of ipilimumab/nivolumab combination have centered around studying lower doses and/or extended dosing schedules of ipilimumab, including ipilimumab 1 mg/kg every 6 or 12 weeks with nivolumab dosed at 3 mg/kg every 2 weeks or 480 mg every 4 weeks. Promising data from a first-line study in NSCLC (CheckMate 012) support the evaluation of nivolumab in combination with lower-dosed ipilimumab (1 mg/kg every 6 or 12 weeks).⁵² This approach is being tested against platinum doublet chemotherapy in a confirmatory phase 3 study in NSCLC (CheckMate 227).

TARGETED THERAPY

MAPK KINASE PATHWAY IN MELANOMA TUMORIGENESIS

The MAPK pathway mediates cellular responses to growth signals. RAF kinases are central mediators in the MAPK pathway and exert their effect primarily through MEK phosphorylation and activation following dimerization (hetero- or homo-) of RAF molecules. As a result, RAF is integral to multiple cellular processes, including transcriptional regulation, cellular differentiation, and cell proliferation. MAPK pathway activation is a common event in many cancers, primarily due to activating mutations in BRAF or RAS. Alternatively, MAPK pathway activation can occur in the absence of activating mutations in BRAF or NRAS through down-regulation of MAPK pathway inhibitory proteins (RAF-1 inhibitory protein or SPRY-2), C-MET overexpression, or activating mutations in non-BRAF/NRAS kinases including CRAF, HRAS, and NRAS.^53,54

Somatic point mutations in BRAF are frequently observed (37%–50%) in malignant melanomas and at lower frequency in a range of human cancers including NSCLC, colorectal cancer, papillary thyroid cancer, ovarian cancer, glioma, and gastrointestinal stromal tumor.^6,55,56BRAF mutations in melanoma typically occur within the activation segment of the kinase domain (exon 15). Between 80% and 90% of activating mutations result in an amino acid substitution of glutamate (E) for valine (V) at position 600: V600E.^57,58 V600E mutations are true oncogenic drivers, resulting in increased kinase activity with demonstrable transformational capacity in vitro. BRAF mutations are usually mutually exclusive, with tumors typically containing no other driver mutations in NRAS, KIT, NF1, or other genes.

NRAS mutations are less common than BRAF mutations, having a reported frequency of 13% to 25% in melanoma.⁴NRAS mutations generally occur within the P-loop region of the G domain (exon 2), or less commonly in the switch II region of the G domain (exon 3). Most NRAS exon 2 mutations comprise amino acid substitutions at position 61 from glutamine (Q) to arginine (R; 35%), lysine (K; 34%) and less often to glutamate (E), leucine (L), or proline (P). Preclinical data suggest that NRAS mutations paradoxically stimulate the MAPK pathway and thus enhance tumor growth in vitro.^59,60 Several important phenotypic differences distinguish NRAS- from BRAF-mutated melanoma. NRAS-mutated tumors are typically associated with increasing age and CSD skin, while BRAF-mutated tumors arise in younger patients in non-CSD skin. A large population-based study suggested that NRAS-mutated melanomas were associated with mitoses and lower tumor infiltrating lymphocytes (TIL) grade, and arose in anatomic sites other than the head/neck, while BRAF-mutated tumors were associated with mitoses and superficial spreading histology.⁶¹ Although the lower TIL grade seen with NRAS-mutated melanomas suggests a more immunosuppressed microenvironment and argues for poorer responses to immune therapies, clinical studies comparing responses to immunotherapies in various categories of driver mutations provide conflicting results for the prognostic role of NRAS mutations in relation to immune checkpoint blockade and other immune therapies.^62–64

NF1 represents the third known driver in cutaneous melanoma, with mutations reported in 12% of cases.^6,7NF1 encodes neurofibromin, which has GTPase activity and regulates RAS proteins; NF1 loss results in increased RAS.⁶⁵ Unlike BRAF or NRAS, which are usually mutually exclusive, NF1 mutations in melanoma can occur singly or in combination with either BRAF or NRAS mutations. In these settings, NF1 mutations are associated with RAS activation, MEK-dependence, and resistance to RAF inhibition.⁶⁶

MAPK PATHWAY INHIBITION SINGLY AND IN COMBINATION

Although multiple MEK 1/2 inhibitors (AS703026, AZD8330/ARRY-704, AZD6244, CH5126766, CI-1040, GSK1120212, PD0325901, RDEA119, and XL518) and RAF inhibitors (ARQ 680, GDC-0879, GSK2118436, PLX4032, RAF265, sorafenib, XL281/BMS-908662) were developed, the initial evaluation of MAPK pathway inhibitors in advanced human cancers began with CI-1040. Preclinical data suggested that CI-1040 potently and selectively inhibited both MEK1 and MEK2, but phase 1 and 2 human trial results were disappointing, likely because these trials were not selectively enriched for NRAS/BRAF–mutated tumors or cancers in which these oncogenic mutations were most commonly detected, such as melanoma.^67,68 The subsequent evaluation of selumetinib (AZD6244/ARRY-142886) in a phase 2 study was also negative. Although investigators enrolled a presumably enriched population (cutaneous melanoma), the incidence of NRAS/BRAF–mutated tumors was not ascertained to determine this, but rather assumed, which led to a discrepancy between the assumed (prestudy) and observed (on-study) proportions of BRAF/NRAS mutations that was not accounted for in power calculations.^69,70 Lessons learned from these earlier misadventures informed the current paradigm of targeted therapy development: (1) identification of a highly specific and potent inhibitor through high-throughput screening; (2) establishment of maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) in unselected patients; (3) confirmation of RP2D in selected tumor types enriched for target of interest; and (4) confirmatory study against standard comparator to seek regulatory approval.

Vemurafenib and dabrafenib were evaluated in this tiered fashion in phase 1 dose-finding studies comprising unselected patients, followed by phase 2 studies in advanced BRAF V600E–mutated melanoma. Both were subsequently evaluated in randomized phase 3 trials (vemurafenib, BRIM-38; dabrafenib, BREAK-310) that compared them with dacarbazine (1000 mg/m² intravenously every 3 weeks) in the treatment of advanced BRAF V600E–mutated melanoma. Response kinetics for both agents were remarkably similar: single-agent BRAF inhibitors resulted in rapid (time to response 2–3 months), profound (approximately 50% objective responses) reductions in tumor burden that lasted 6 to 7 months. Adverse events common to both agents included rash, fatigue, and arthralgia, although clinically significant photosensitivity was more common with vemurafenib and clinically significant pyrexia was more common with dabrafenib. Class-specific adverse events included the development of cutaneous squamous-cell carcinomas and keratoacanthomas secondary to paradoxical activation of MAPK pathway signaling either through activating mutations in HRAS or mutations or amplifications in receptor tyrosine kinases upstream of BRAF, resulting in elevated levels of RAS–guanosine triphosphate complexes.⁷¹ Results of these studies resulted in regulatory approval of single-agent BRAF inhibitors for the treatment of BRAF V600E (and later V600K)–mutated melanoma (vemurafenib in 2011; dabrafenib in 2013). Details regarding trial populations, study interventions, efficacy, and adverse events are summarized in Table 2.

Responses to BRAF inhibitors are typically profound but temporary. Mechanisms of acquired resistance are diverse and include reactivation of MAPK pathway–dependent signaling (RAS activation or increased RAF expression), and development of MAPK pathway–independent signaling (COT overexpression; increased PI3K or AKT signaling) that permits bypass of inhibited BRAF signaling within the MAPK pathway.^72–76 These findings suggested that upfront inhibition of both MEK and mutant BRAF may produce more durable responses than BRAF inhibition alone. Three pivotal phase 3 studies established the superiority of combination BRAF and MEK inhibition over BRAF inhibition alone: COMBI-d11 (dabrafenib/trametinib versus dabrafenib/placebo), COMBI-v12 (dabrafenib/trametinib versus vemurafenib), and coBRIM13 (vemurafenib/cobimetinib versus vemurafenib/placebo). As expected, compared to BRAF inhibitor monotherapy, combination BRAF and MEK inhibition produced greater responses and improved progression-free and overall survival (Table 2). Interestingly, the rate of cutaneous squamous-cell carcinomas was much lower with combination therapy, reflecting the more profound degree of MAPK pathway inhibition achieved with combination BRAF and MEK inhibition. Based on these results, FDA approval was granted for both dabrafenib/trametinib and vemurafenib/cobimetinib combinations in 2015. Although the dabrafenib/trametinib combination was only approved in 2015, trametinib had independently gained FDA approval in 2013 for the treatment of BRAF V600E/K–mutated melanoma on the basis of the phase 3 METRIC study.⁷⁷

Encorafenib (LGX818) and binimetinib (MEK162, ARRY-162, ARRY-438162) are new BRAF and MEK inhibitors currently being evaluated in clinical trials. Encorafenib/binimetinib combination was first evaluated in a phase 3 study (COLUMBUS) that compared it with vemurafenib monotherapy in BRAF-mutant melanoma.⁷⁸ Unsurprisingly, encorafenib/binimetinib combination produced greater and more durable responses compared to vemurafenib monotherapy. The median progression-free survival of the encorafenib/binimetinib combination (14.9 months) was greater than vemurafenib monotherapy (7.3 months) in this study, and intriguingly greater than that seen with vemurafenib/cobimetinib (coBRIM 9.9 months) and dabrafenib/trametinib (COMBI-d 9.3 months; COMBI-v 11.4 months). Of note, although encorafenib has an IC50 midway between dabrafenib and vemurafenib in cell-free assays (0.8 nM dabrafenib, 4 nM encorafenib, and 31 nM vemurafenib), it has an extremely slower off-rate from BRAF V600E, which results in significantly greater target inhibition in cells following drug wash-out.⁷⁹ This may account for the significantly greater clinical benefit seen with encorafenib/binimetinib in clinical trials. Final study data are eagerly awaited. Regulatory approval has been sought, and is pending at this time.

Binimetinib has been compared to dacarbazine in a phase 3 study (NEMO) of patients with NRAS-mutant melanoma, most of whom had been previously treated with immunotherapy.⁸⁰ Response rates were low in both arms, although slightly greater with binimetinib than dacarbazine (15% versus 9%), commensurate with a modest improvement in progression-free survival. FDA approval has been sought and remains pending at this time.

KIT INHIBITION SINGLY AND IN COMBINATION

The KIT receptor protein tyrosine kinase is a transmembrane protein consisting of extracellular and intracellular domains. Activating KIT mutations occur in 2% to 8% of all melanoma patients and may be found in all melanoma subtypes but are commonest in acral melanomas (10%–20%) and mucosal melanomas (15%–20%). Activating KIT mutations primarily occur in exons 11 and 13, which code for the juxtamembrane and kinase domains, respectively.^5,81–83

Imatinib mesylate is a tyrosine kinase inhibitor of the 2-phenyl amino pyrimidine class that occupies the tyrosine kinase active site with resultant blocking of tyrosine kinase activity. Imatinib mesylate is known to block KIT and has been extensively studied in patients with gastrointestinal stromal tumors (GIST), 80% of whom harbor KIT mutations, in both the adjuvant and the metastatic settings. In melanoma, imatinib mesylate was studied in a Chinese open-label, phase 2 study of imatinib mesylate monotherapy in metastatic melanoma harboring KIT mutation or amplification; 25% of the study patients had mucosal disease and the rest had cutaneous disease, with acral involvement in 50% of all patients.⁸⁴ Overall response rate was 23%, while 51% of patients remained alive at 1 year with no differences in response rate and/or survival being noted between patients with either KIT mutations or amplifications. In a separate study of imatinib mesylate at 400 mg daily or 400 mg twice daily in Caucasian patients with KIT-mutated/amplified melanoma, similar response and survival rates were reported, although patients with KIT mutations did nonsignificantly better than those with KIT amplifications.⁸⁵

Other novel studies evaluating KIT inhibitors include KIT inhibition in combination with the VEGF inhibitor bevacizumab and a study of selective BCR-ABL kinase inhibitor nilotinib in imatinib-resistant melanoma. In the former phase 1/2 study, Flaherty and colleagues studied imatinib 800 mg daily and bevacizumab at 10 mg/kg every 2 weeks in 63 patients with advanced tumors, including 23 with metastatic melanoma. Although the combination was relatively nontoxic, no significant efficacy signal was seen and further accrual to the phase 2 portion was halted after the first stage was completed.⁸⁶ Nilotinib is a BCR-ABL1 tyrosine kinase inhibitor intelligently designed based on the structure of the ABL-imatinib complex that is 10 to 30 times more potent than imatinib in inhibiting BCR-ABL1 tyrosine kinase activity. Nilotinib is approved for the treatment of imatinib-resistant chronic myelogenous leukemia (CML), with reported efficacy in patients with central nervous system (CNS) involvement.^87,88 Nilotinib has been studied in a single study of KIT-mutated/amplified melanoma that included patients with imatinib-resistance and those with treated CNS disease. Nilotinib appeared to be active in imatinib-resistant melanoma, although no responses were seen in the CNS disease cohort.⁸⁹ Overall, the response rates observed with KIT inhibition in melanoma are much lower than those observed in CML and GIST.

CONCLUSION AND FUTURE DIRECTIONS

Prior to 2011, the only approved agents for the treatment of advanced melanoma were dacarbazine and high-dose interleukin-2. Since 2011, drug approvals in melanoma have proceeded at a frenetic pace unmatched in any other disease. The primary events underlying this are advances in our understanding of the gene mutation landscape driving melanoma tumorigenesis, accompanied by insights into the means by which tumors circumvent the induction of effective anti-tumor T-cell responses. These insights have resulted in the development of inhibitors targeting MAPK pathway kinases BRAF, MEK, and NRAS), KIT, and regulatory immune checkpoints (CTLA-4 and PD-1). Although BRAF/MEK inhibition results in profound reductions and even occasional complete responses in patients, these responses are typically short lived, rarely lasting more than 9 to 11 months; the encorafenib/binimetinib combination may improve that duration marginally. However, the signature therapeutic advance in melanoma of the past decade is immunotherapy, particularly the development of inhibitors of CTLA-4 and PD-1 immune checkpoints. With these agents, significant proportions of treated patients remain free of progression off-therapy (ipilimumab 23%; nivolumab 34%; pembrolizumab 35%; ipilimumab/nivolumab 64%), and some patients can be successfully re-induced after delayed progression. Separately, the high response rates observed with the use of KIT inhibitors in CML and GIST have not been observed in KIT mutated/amplified melanoma and development of agents in this space has been limited. The challenges ahead center around identifying predictive biomarkers and circumventing primary or acquired resistance, with the eventual goal of producing durable remissions in the majority of treated patients.

Our improved understanding of the mechanisms of acquired resistance to BRAF/MEK inhibitors suggests that anti-tumor activity may be achieved by targeting multiple pathways, possibly with combination regimens comprising other inhibitors and/or immunotherapy. Preclinical data supports the use of combination strategies targeting both ERK and PI3K/mTOR to circumvent acquired resistance.⁹⁰ Ongoing studies are evaluating combinations with biguanides (metformin: NCT02143050 and NCT01638676; phenformin: NCT03026517), HSP90 inhibitors (XL888: NCT02721459; AT13387: NCT02097225), and decitabine (NCT01876641).

One complexity affecting management of resistance in the targeted therapy landscape remains tumor heterogeneity, particularly intra- and intertumoral heterogeneity, which may explain the apparent contradiction between continued efficacy of BRAF inhibitors in BRAF-resistant tumors and preclinical data predicting slower progression of resistant tumors on cessation of BRAF inhibitors.^91–94 These data provide a rationale to investigate intermittent dosing regimens with BRAF/MEK inhibitors; several studies exploring this approach are ongoing (NCT01894672 and NCT02583516).

Given the specificity, adaptability, and memory response associated with immunotherapy, it is likely that these agents will be used to treat the majority of patients regardless of mutational status. Hence, identifying predictive biomarkers of response to immune checkpoint inhibitors is vital. The presence of CD8+ T-cell infiltrate and IFN-γ gene signature, which indicate an “inflamed” tumor microenvironment, are highly predictive of clinical benefit from PD-1 inhibitors.^95,96 However, not all PD-1 responders have “inflamed” tumor microenvironments, and not all patients with an “inflamed” tumor microenvironment respond to immune checkpoint inhibitors. The complexity of the immune system is reflected in the multiple non-redundant immunologic pathways, both positive and negative, with checkpoints and ligands that emerge dynamically in response to treatment. Given the dynamic nature of the immune response, it is unlikely that any single immunologic biomarker identified pre-treatment will be completely predictive. Rather, the complexity of the biomarker approach must match the complexity of the immune response elicited, and will likely incorporate multifarious elements including CD8+ T-cell infiltrate, IFN-γ gene signature, and additional elements including microbiome, genetic polymorphisms, and tumor mutation load. The goal is to use multiple markers to guide development of combinations and then, depending on initial response, to examine tumors for alterations to guide decisions about additional treatment(s) to improve responses, with the eventual goal being durable clinical responses for all patients.

INTRODUCTION

The incidence of cutaneous melanoma has increased over the past 2 decades, with SEER estimates indicating that the number of new cases of melanoma diagnosed annually rose from 38,300 in 1996 to 76,000 in 2016.¹ Among persons younger than 50 years, the incidence is higher in females, and younger women (aged 15–39 years) are especially vulnerable.² Among persons older than 50, melanoma incidence in men is nearly twice that of women, in whom melanomas are often thicker and often associated with worse outcomes.^1,2 Approximately 85% of melanomas are diagnosed at early stages when surgery is curative, but the lifetime probability of developing invasive disease is 3% in men and 2% in women.

Prior to the advent of effective immunotherapies and targeted therapies, melanoma was often managed with chemotherapy, which had dismal response rates and commensurately poor outcomes. Advances in the understanding of the molecular etiopathogenesis and immune escape responses of cutaneous metastatic melanoma have transformed therapeutic approaches. Specifically, improved understanding of the genetic mutations driving melanoma tumorigenesis coupled with insights into mechanisms of tumor-mediated immune evasion resulted in development of inhibitors of mitogen-activated protein kinases (MAPK; BRAF and MEK) along with inhibitors of negative regulatory immune checkpoints (cytotoxic T lymphocyte–associated antigen 4 [CTLA-4] and programmed cell death-1 [PD-1]). In this review, we discuss the role of immune therapy, targeted therapy, and combinations of these in the treatment of metastatic cutaneous melanoma. We limit the immuno-therapy discussion to approved CTLA-4/PD-1 inhibitors and the targeted therapy discussion to approved BRAF/NRAS/MEK inhibitors and do not discuss non-checkpoint immunotherapies including cytokines (HD IL-2), vaccines, or adoptive T-cell approaches. Interested readers are directed to other excellent works covering these important topics.^26–29

DEVELOPMENT OF TARGETED AND NOVEL IMMUNE THERAPIES

For many years the degree of ultraviolet (UV) light exposure was considered the sole major risk factor for melanoma oncogenesis, even though its mechanism was largely unknown.³ However, clinical observations regarding the occurrence of melanoma on less exposed areas (trunk and limbs) in individuals with intermittent sun exposure led to the proposition that melanomas that arose in younger patients with intermittent sun exposure were distinct from melanomas that arose in older patients in association with markers of chronic sun exposure—the “divergent pathway” hypothesis.³ Critical to this understanding were whole-exome sequencing data from multiple groups, including The Cancer Genome Atlas, that identified patterns of mutations in oncogenic drivers that were distinct in patients with and without chronically sun-damaged (CSD) skin.^4–7 It is now clear that based on its association with CSD skin, melanoma can be subclassified into CSD or non-CSD melanoma. CSD and non-CSD melanoma have distinct clinico-pathological characteristics and are associated with different driver mutations. CSD melanomas typically arise in older patients on sun-exposed areas (head/neck, dorsal surfaces of distal extremities) and are associated with particular driver mutations (BRAF non-V600E, NRAS, NF1, or KIT) and genetic signatures of UV-induced DNA damage (G > T [UVA] or C > T [UVB]) transitions. Conversely, non-CSD melanomas typically arise in younger (< 55 years) patients on intermittently sun-exposed areas (trunk, proximal extremities) and are associated with BRAF V600E/K driver mutations and often lack genetic signatures of UV mutagenesis.

Identification of driver mutations in components of the MAPK pathway, including BRAF and NRAS, facilitated the development of targeted inhibitors. The BRAF inhibitors vemurafenib and dabrafenib have been shown in pivotal phase 3 studies to significantly improve overall and progression-free survival in patients with metastatic melanoma compared with chemotherapy and garnered regulatory approval (vemurafenib, BRIM-3;^8,9 dabrafenib, BREAK-3¹⁰). Concomitant MEK and BRAF inhibition extends the duration of benefit by preventing downstream kinase activation in the MAPK pathway. Notably, concomitant MEK inhibition alters the side-effect profile of BRAF inhibitors, with reduced incidence of keratoacanthomas and cutaneous squamous cell carcinomas that are attributable to on-target, off-tumor effects of BRAF inhibitors. Combined BRAF and MEK inhibition (vemurafenib/cobimetinib and dabrafenib/trametinib) further improved overall and progression-free survival compared to single-agent BRAF inhibition in phase 3 studies (COMBI-d,¹¹ COMBI-v,¹² and coBRIM¹³). Although often deep, the responses seen with the use of targeted kinase inhibitors are not often durable, with the vast majority of patients progressing after 12 to 15 months of therapy.In parallel, work primarily done in murine models of chronic viral infection uncovered the role played by co-inhibitory or co-excitatory immune checkpoints in mediating T-cell immune responses. These efforts clarified that tumor-mediated immune suppression primarily occurs through enhancement of inhibitory signals via the negative T-cell immune checkpoints CTLA-4 or PD-1.^14,15 Blockade of negative T-cell immune checkpoints resulted in activation of the adaptive immune system, resulting in durable anti-tumor responses as demonstrated in studies of the CTLA-4 inhibitor ipilimumab (CA184-020¹⁶ and CA184-024¹⁷) and the PD-1 inhibitors nivolumab (CA209-003,¹⁸ CheckMate 037,¹⁹ and CheckMate 066²⁰) and pembrolizumab (KEYNOTE-001²¹ and KEYNOTE-006²²). Compared to the deep but short-lived responses seen with targeted kinase inhibitors, patients treated with CTLA-4 or PD-1 immune checkpoint blockade often developed durable responses that persisted even after completion of therapy. Combined CTLA-4 and PD-1 blockade results in greater magnitude of response with proportionately increased toxicity.^23–25

IMMUNOTHERAPY

CTLA-4 AND PD-1 IMMUNE CHECKPOINT INHIBITORS

The novel success of immunotherapy in recent decades is largely attributable to improved understanding of adaptive immune physiology, specifically T-cell activation and regulation. T-cell activation requires 2 independent signaling events: it is initiated upon recognition of the antigen-MHC class II-receptor complex on antigen-presenting cells (APC), and requires a secondary co-stimulatory interaction of CD80/CD86 (B7.1/B7.2) on APCs and CD28 molecule on T-cells; without this second event, T-cells enter an anergic state.^30–32 Upon successful signaling and co-stimulation, newly activated T-cells upregulate CTLA-4, which can bind to B7 molecules with a nearly 100-fold greater affinity than CD28.^33,34 Unlike CD28, CTLA-4 engagement negatively regulates T-cell activation. The opposing signals produced by CD28 and CTLA-4 are integrated by the T-cell to determine eventual response to activation, and provide a means by which T-cell activation is homeostatically regulated to prevent exaggerated physiologic immune responses.³⁵ It was hypothesized that CTLA-4 blockade would permit T-cell activation, which is thwarted in the tumor microenvironment by tumor-mediated CTLA-4 engagement, thereby unleashing an anti-tumor immune response.³⁶

PD-1 is a member of the CD28 and CTLA-4 immunoglobulin super family and, similar to CTLA-4, binds activated T-cells. PD-1 has 2 ligands on activated T-cells: PD-L1 and PD-L2.³⁷ PD-L1 is constitutively expressed by a variety of immune and non-immune cells, particularly in inflammatory environments including tumor microenvironments, in response to the release of inflammatory cytokines such as interferon (IFN)-γ.^37,38 Conversely, PD-L2 is only minimally expressed constitutively, although its expression on immune and non-immune cells can be induced by similar cues from inflammatory microenvironments. PD-L1 and PD-L2 cross-compete for binding to PD-1, with PD-L2 exhibiting 2- to 6-fold greater relative affinity than PD-L1.³⁹ PD-L1/PD-1 binding results in phosphorylation of 2 tyrosinases in the intracellular portion of PD-1, which contains immunoreceptor tyrosine-based inhibitory motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM). PD-1 ITSM subsequently recruits either of 2 SH2-domain–containing protein tyrosine phosphatases: SHP-1 and SHP-2. SHP-2 signaling suppresses PI3K/Akt activation, down-regulates Bcl-xL, and suppresses expression of multiple transcription factors that mediate T-cell effector function including GATA-3, Eomes, and T-bet.^40–42 The net effect of PD-L1/PD-1 engagement is to suppress T-cell proliferation, cytokine production, cytolytic function, and survival. Unlike CTLA-4, which primarily affects the priming phase of naive T-cell activation, PD-1 chiefly regulates the effector phase of T-cell function. Furthermore, because PD-L1/PD-L2 expression is limited to inflammatory microenvironments, the effects of PD-1 are less generalized than those of CTLA-4.

SINGLE AGENT ACTIVITY OF CTLA-4 AND PD-1 INHIBITORS

Ipilimumab (MDX-010) is a human IgG1 monoclonal antibody shown to inhibit CTLA-4.⁴³ Early studies tested different formulations (transfectoma-derived and hybridoma-derived), doses, and schedules of ipilimumab primarily in patients with advanced refractory melanoma.^44–46 Although responses were infrequent, responding patients experienced durable remissions at 1- and 2-year time points. Notably, in a foreshadowing of changes to response criteria used to evaluate these agents, several treated patients who initially had radiographically stable disease upon completion of therapy subsequently experienced a gradual decline in tumor burden.

Ipilimumab was subsequently evaluated in 2 phase 3 trials. The first study (MDX010-020/CA184-020), which involved 676 HLA-A*0201–positive patients with advanced melanoma, compared ipilimumab 3 mg/kg every 3 weeks for 4 doses either singly or in combination with gp100 vaccine with a gp100-only control arm.¹⁶ Ipilimumab administration resulted in objective responses in 11% of patients and improved progression-free and overall survival compared to gp100 alone. Of note, ipilimumab monotherapy was superior to ipilimumab/gp100 combination, possibly related to timing of vaccine in relation to ipilimumab. A confirmatory study (CA184-024) compared a higher dose of ipilimumab (10 mg/kg) in combination with dacarbazine to dacarbazine monotherapy in previously untreated melanoma and was positive.¹⁷ Given the lack of augmented efficacy with the higher (10 mg/kg) dose, ipilimumab received regulatory approval in 2011 for the treatment of melanoma at the lower dose: 3 mg/kg administered every 3 weeks for 4 doses (Table 1). Survival data was strikingly similar to patterns observed in prior phase 2 studies, with survival curves plateauing after 2 years at 23.5% to 28.5% of treated patients. Pooled survival data from prospective and retrospective studies of ipilimumab corroborate the plateau of 22% (26% treated; 20% untreated) reached at year 3 regardless of prior therapy or ipilimumab dose, underscoring the durability of long-term survival in ipilimumab-treated patients.⁴⁷ Ipilimumab administration resulted in an unusual spectrum of toxicities including diarrhea, rash, hepatitis, and hypophysitis (termed immune-related adverse events, or irAEs) in up to a third of patients.

Pembrolizumab and nivolumab are humanized IgG4 monoclonal antibodies that target the PD-1 receptor found on activated T cells, B cells, and myeloid cells. Pembrolizumab and nivolumab are engineered similarly: by immunizing transgenic mice with recombinant human PD-1-Fc protein and subsequently screening murine splenic cells fused with myeloma cells for hybridomas producing antibodies reactive to PD-1-Fc.^48,49 Unlike IgG1, the IgG4 moiety neither engages Fc receptors nor activates complement, avoiding cytotoxic effects of the antibody upon binding to the T cells that it is intended to activate. Both pembrolizumab and nivolumab bind PD-1 with high affinity and specificity, effectively inhibiting the interaction between PD-1 and ligands PD-L1 and PD-L2.

Nivolumab was first studied in a phase 1 study (CA209-003) of 296 patients with advanced cancers who received 1, 3, or 10 mg/kg administered every 2 weeks.¹⁸ Histologies tested included melanoma, non–small-cell lung cancer (NSCLC), renal-cell cancer (RCC), castration-resistant prostate cancer (CRPC), and colorectal cancer (CRC). Responses were seen in melanoma and RCC and unusually in NSCLC, including in both squamous and non-squamous tumors. Objective responses were noted in 41% of the 107 melanoma patients treated at 3 mg/kg. Survival was improved, with 1- and 2-year survival rates of 62% and 43% at extended follow up.⁵⁰

Subsequently, nivolumab was compared to chemotherapy in a pair of phase 3 studies involving both previously untreated (Checkmate 066) and ipilimumab/BRAF inhibitor–refractory (CheckMate 037) patients.^19,20 In both studies, nivolumab produced durable responses in 32% to 34% of patients and improved survival over chemotherapy. Compared to ipilimumab, the incidence of irAEs was much lower with nivolumab. The depth and magnitude of responses observed led to regulatory approval for nivolumab in both indications (untreated and ipilimumab/BRAF inhibitor–treated melanoma) in 2014. Data from both studies are summarized in Table 1.

Pembrolizumab was first evaluated in a phase 1 study of 30 patients with a variety of solid organ malignancies in which no dose-limiting toxicities were observed and no defined maximal tolerated dose was reached.⁵¹ Per protocol, maximal administered dose was 10 mg/kg every 2 weeks. Following startling responses including 2 complete responses of long duration, pembrolizumab was evaluated in a large phase 1 study (KEYNOTE-001) of 1260 patients that evaluated 3 doses (10 mg/kg every 2 weeks, 10 mg/kg every 3 weeks, and 2 mg/kg every 3 weeks) in separate melanoma and NSCLC substudies.²¹ Both ipilimumab-naïve and ipilimumab-treated patients were enrolled in the melanoma substudy. Objective responses were seen in 38% ofpatients across all 3 dosing schedules and were similar in both ipilimumab-naïve and ipilimumab-treated patients. Similar to nivolumab, most responders experienced durable remissions.

Pembrolizumab was subsequently compared to ipilimumab in untreated patients (KEYNOTE-006) in which patients were randomly assigned to receive either ipilimumab or pembrolizumab at 1 of 2 doses: 10 mg/kg every 2 weeks and pembrolizumab 10 mg/kg every 3 weeks.²² Response rates were greater with pembrolizumab than ipilimumab, with commensurately greater 1-year survival rates. Rates of treatment-related adverse events requiring discontinuation of study drug were much lower with pembrolizumab than ipilimumab. This trial was instrumental in proving the superior profile of pembrolizumab over ipilimumab. The US Food and Drug Administration (FDA) granted pembrolizumab accelerated approval for second-line treatment of melanoma in 2014, and updated this to include a first-line indication in 2015 (Table 1).

EFFICACY OF COMBINED CTLA-4 AND PD-1 INHIBITION

Preclinical studies demonstrated that PD-1 blockade was more effective than CTLA-4 blockade and combination PD-1/CTLA-4 blockade was synergistic, with complete rejection of tumors in approximately half of the treated animals.¹⁴ This hypothesis was evaluated in a phase 1 study that explored both concurrent and sequential combinations of ipilimumab and nivolumab along with increasing doses of both agents in PD-1/CTLA-4–naïve advanced melanoma.²³ Responses were greater in the concurrent arm (40%) than in the sequential arm (20%) across dose-levels with a small fraction of patients treated in the concurrent arm experiencing a profound reduction (80%) in tumor burden.

The superiority of ipilimumab/nivolumab combination to ipilimumab monotherapy was demonstrated in a randomized blinded phase 2 study (CheckMate 069).²⁴ Of the 4 different ipilimumab/nivolumab doses explored in the phase 1 study (3 mg/kg and 0.3 mg/kg, 3 mg/kg and 1 mg/kg, 1 mg/kg and 3 mg/kg, 3 mg/kg and 3 mg/kg), ipilimumab 3 mg/kg and nivolumab 1 mg/kg (followed by nivolumab 3 mg/kg) was compared to ipilimumab and nivolumab-matched placebo. Responses were significantly greater with dual PD-1/CTLA-4 blockade compared to CTLA-4 blockade alone (59% versus 11%). Concurrently, a 3-arm randomized phase 3 study compared the same dose of ipilimumab/nivolumab to ipilimumab and nivolumab in previously untreated advanced melanoma (CheckMate 067).²⁵ Similar to CheckMate 069, CheckMate 067 demonstrated that ipilimumab/nivolumab combination resulted in more profound responses (58%) than either ipilimumab (19%) or nivolumab (44%) alone. Toxicity, primarily diarrhea, fatigue, pruritus, and rash, was considerable in the combination arm (55% grade 3/4 adverse events) and resulted in treatment discontinuation in 30% of patients. The profound and durable responses observed led to accelerated approval of ipilimumab/nivolumab combination in 2015 (Table 1).

Efforts to improve the toxicity/benefit ratio of ipilimumab/nivolumab combination have centered around studying lower doses and/or extended dosing schedules of ipilimumab, including ipilimumab 1 mg/kg every 6 or 12 weeks with nivolumab dosed at 3 mg/kg every 2 weeks or 480 mg every 4 weeks. Promising data from a first-line study in NSCLC (CheckMate 012) support the evaluation of nivolumab in combination with lower-dosed ipilimumab (1 mg/kg every 6 or 12 weeks).⁵² This approach is being tested against platinum doublet chemotherapy in a confirmatory phase 3 study in NSCLC (CheckMate 227).

TARGETED THERAPY

MAPK KINASE PATHWAY IN MELANOMA TUMORIGENESIS

The MAPK pathway mediates cellular responses to growth signals. RAF kinases are central mediators in the MAPK pathway and exert their effect primarily through MEK phosphorylation and activation following dimerization (hetero- or homo-) of RAF molecules. As a result, RAF is integral to multiple cellular processes, including transcriptional regulation, cellular differentiation, and cell proliferation. MAPK pathway activation is a common event in many cancers, primarily due to activating mutations in BRAF or RAS. Alternatively, MAPK pathway activation can occur in the absence of activating mutations in BRAF or NRAS through down-regulation of MAPK pathway inhibitory proteins (RAF-1 inhibitory protein or SPRY-2), C-MET overexpression, or activating mutations in non-BRAF/NRAS kinases including CRAF, HRAS, and NRAS.^53,54

Somatic point mutations in BRAF are frequently observed (37%–50%) in malignant melanomas and at lower frequency in a range of human cancers including NSCLC, colorectal cancer, papillary thyroid cancer, ovarian cancer, glioma, and gastrointestinal stromal tumor.^6,55,56BRAF mutations in melanoma typically occur within the activation segment of the kinase domain (exon 15). Between 80% and 90% of activating mutations result in an amino acid substitution of glutamate (E) for valine (V) at position 600: V600E.^57,58 V600E mutations are true oncogenic drivers, resulting in increased kinase activity with demonstrable transformational capacity in vitro. BRAF mutations are usually mutually exclusive, with tumors typically containing no other driver mutations in NRAS, KIT, NF1, or other genes.

NRAS mutations are less common than BRAF mutations, having a reported frequency of 13% to 25% in melanoma.⁴NRAS mutations generally occur within the P-loop region of the G domain (exon 2), or less commonly in the switch II region of the G domain (exon 3). Most NRAS exon 2 mutations comprise amino acid substitutions at position 61 from glutamine (Q) to arginine (R; 35%), lysine (K; 34%) and less often to glutamate (E), leucine (L), or proline (P). Preclinical data suggest that NRAS mutations paradoxically stimulate the MAPK pathway and thus enhance tumor growth in vitro.^59,60 Several important phenotypic differences distinguish NRAS- from BRAF-mutated melanoma. NRAS-mutated tumors are typically associated with increasing age and CSD skin, while BRAF-mutated tumors arise in younger patients in non-CSD skin. A large population-based study suggested that NRAS-mutated melanomas were associated with mitoses and lower tumor infiltrating lymphocytes (TIL) grade, and arose in anatomic sites other than the head/neck, while BRAF-mutated tumors were associated with mitoses and superficial spreading histology.⁶¹ Although the lower TIL grade seen with NRAS-mutated melanomas suggests a more immunosuppressed microenvironment and argues for poorer responses to immune therapies, clinical studies comparing responses to immunotherapies in various categories of driver mutations provide conflicting results for the prognostic role of NRAS mutations in relation to immune checkpoint blockade and other immune therapies.^62–64

NF1 represents the third known driver in cutaneous melanoma, with mutations reported in 12% of cases.^6,7NF1 encodes neurofibromin, which has GTPase activity and regulates RAS proteins; NF1 loss results in increased RAS.⁶⁵ Unlike BRAF or NRAS, which are usually mutually exclusive, NF1 mutations in melanoma can occur singly or in combination with either BRAF or NRAS mutations. In these settings, NF1 mutations are associated with RAS activation, MEK-dependence, and resistance to RAF inhibition.⁶⁶

MAPK PATHWAY INHIBITION SINGLY AND IN COMBINATION

Although multiple MEK 1/2 inhibitors (AS703026, AZD8330/ARRY-704, AZD6244, CH5126766, CI-1040, GSK1120212, PD0325901, RDEA119, and XL518) and RAF inhibitors (ARQ 680, GDC-0879, GSK2118436, PLX4032, RAF265, sorafenib, XL281/BMS-908662) were developed, the initial evaluation of MAPK pathway inhibitors in advanced human cancers began with CI-1040. Preclinical data suggested that CI-1040 potently and selectively inhibited both MEK1 and MEK2, but phase 1 and 2 human trial results were disappointing, likely because these trials were not selectively enriched for NRAS/BRAF–mutated tumors or cancers in which these oncogenic mutations were most commonly detected, such as melanoma.^67,68 The subsequent evaluation of selumetinib (AZD6244/ARRY-142886) in a phase 2 study was also negative. Although investigators enrolled a presumably enriched population (cutaneous melanoma), the incidence of NRAS/BRAF–mutated tumors was not ascertained to determine this, but rather assumed, which led to a discrepancy between the assumed (prestudy) and observed (on-study) proportions of BRAF/NRAS mutations that was not accounted for in power calculations.^69,70 Lessons learned from these earlier misadventures informed the current paradigm of targeted therapy development: (1) identification of a highly specific and potent inhibitor through high-throughput screening; (2) establishment of maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) in unselected patients; (3) confirmation of RP2D in selected tumor types enriched for target of interest; and (4) confirmatory study against standard comparator to seek regulatory approval.

Vemurafenib and dabrafenib were evaluated in this tiered fashion in phase 1 dose-finding studies comprising unselected patients, followed by phase 2 studies in advanced BRAF V600E–mutated melanoma. Both were subsequently evaluated in randomized phase 3 trials (vemurafenib, BRIM-38; dabrafenib, BREAK-310) that compared them with dacarbazine (1000 mg/m² intravenously every 3 weeks) in the treatment of advanced BRAF V600E–mutated melanoma. Response kinetics for both agents were remarkably similar: single-agent BRAF inhibitors resulted in rapid (time to response 2–3 months), profound (approximately 50% objective responses) reductions in tumor burden that lasted 6 to 7 months. Adverse events common to both agents included rash, fatigue, and arthralgia, although clinically significant photosensitivity was more common with vemurafenib and clinically significant pyrexia was more common with dabrafenib. Class-specific adverse events included the development of cutaneous squamous-cell carcinomas and keratoacanthomas secondary to paradoxical activation of MAPK pathway signaling either through activating mutations in HRAS or mutations or amplifications in receptor tyrosine kinases upstream of BRAF, resulting in elevated levels of RAS–guanosine triphosphate complexes.⁷¹ Results of these studies resulted in regulatory approval of single-agent BRAF inhibitors for the treatment of BRAF V600E (and later V600K)–mutated melanoma (vemurafenib in 2011; dabrafenib in 2013). Details regarding trial populations, study interventions, efficacy, and adverse events are summarized in Table 2.

Responses to BRAF inhibitors are typically profound but temporary. Mechanisms of acquired resistance are diverse and include reactivation of MAPK pathway–dependent signaling (RAS activation or increased RAF expression), and development of MAPK pathway–independent signaling (COT overexpression; increased PI3K or AKT signaling) that permits bypass of inhibited BRAF signaling within the MAPK pathway.^72–76 These findings suggested that upfront inhibition of both MEK and mutant BRAF may produce more durable responses than BRAF inhibition alone. Three pivotal phase 3 studies established the superiority of combination BRAF and MEK inhibition over BRAF inhibition alone: COMBI-d11 (dabrafenib/trametinib versus dabrafenib/placebo), COMBI-v12 (dabrafenib/trametinib versus vemurafenib), and coBRIM13 (vemurafenib/cobimetinib versus vemurafenib/placebo). As expected, compared to BRAF inhibitor monotherapy, combination BRAF and MEK inhibition produced greater responses and improved progression-free and overall survival (Table 2). Interestingly, the rate of cutaneous squamous-cell carcinomas was much lower with combination therapy, reflecting the more profound degree of MAPK pathway inhibition achieved with combination BRAF and MEK inhibition. Based on these results, FDA approval was granted for both dabrafenib/trametinib and vemurafenib/cobimetinib combinations in 2015. Although the dabrafenib/trametinib combination was only approved in 2015, trametinib had independently gained FDA approval in 2013 for the treatment of BRAF V600E/K–mutated melanoma on the basis of the phase 3 METRIC study.⁷⁷

Encorafenib (LGX818) and binimetinib (MEK162, ARRY-162, ARRY-438162) are new BRAF and MEK inhibitors currently being evaluated in clinical trials. Encorafenib/binimetinib combination was first evaluated in a phase 3 study (COLUMBUS) that compared it with vemurafenib monotherapy in BRAF-mutant melanoma.⁷⁸ Unsurprisingly, encorafenib/binimetinib combination produced greater and more durable responses compared to vemurafenib monotherapy. The median progression-free survival of the encorafenib/binimetinib combination (14.9 months) was greater than vemurafenib monotherapy (7.3 months) in this study, and intriguingly greater than that seen with vemurafenib/cobimetinib (coBRIM 9.9 months) and dabrafenib/trametinib (COMBI-d 9.3 months; COMBI-v 11.4 months). Of note, although encorafenib has an IC50 midway between dabrafenib and vemurafenib in cell-free assays (0.8 nM dabrafenib, 4 nM encorafenib, and 31 nM vemurafenib), it has an extremely slower off-rate from BRAF V600E, which results in significantly greater target inhibition in cells following drug wash-out.⁷⁹ This may account for the significantly greater clinical benefit seen with encorafenib/binimetinib in clinical trials. Final study data are eagerly awaited. Regulatory approval has been sought, and is pending at this time.

Binimetinib has been compared to dacarbazine in a phase 3 study (NEMO) of patients with NRAS-mutant melanoma, most of whom had been previously treated with immunotherapy.⁸⁰ Response rates were low in both arms, although slightly greater with binimetinib than dacarbazine (15% versus 9%), commensurate with a modest improvement in progression-free survival. FDA approval has been sought and remains pending at this time.

KIT INHIBITION SINGLY AND IN COMBINATION

The KIT receptor protein tyrosine kinase is a transmembrane protein consisting of extracellular and intracellular domains. Activating KIT mutations occur in 2% to 8% of all melanoma patients and may be found in all melanoma subtypes but are commonest in acral melanomas (10%–20%) and mucosal melanomas (15%–20%). Activating KIT mutations primarily occur in exons 11 and 13, which code for the juxtamembrane and kinase domains, respectively.^5,81–83

Imatinib mesylate is a tyrosine kinase inhibitor of the 2-phenyl amino pyrimidine class that occupies the tyrosine kinase active site with resultant blocking of tyrosine kinase activity. Imatinib mesylate is known to block KIT and has been extensively studied in patients with gastrointestinal stromal tumors (GIST), 80% of whom harbor KIT mutations, in both the adjuvant and the metastatic settings. In melanoma, imatinib mesylate was studied in a Chinese open-label, phase 2 study of imatinib mesylate monotherapy in metastatic melanoma harboring KIT mutation or amplification; 25% of the study patients had mucosal disease and the rest had cutaneous disease, with acral involvement in 50% of all patients.⁸⁴ Overall response rate was 23%, while 51% of patients remained alive at 1 year with no differences in response rate and/or survival being noted between patients with either KIT mutations or amplifications. In a separate study of imatinib mesylate at 400 mg daily or 400 mg twice daily in Caucasian patients with KIT-mutated/amplified melanoma, similar response and survival rates were reported, although patients with KIT mutations did nonsignificantly better than those with KIT amplifications.⁸⁵

Other novel studies evaluating KIT inhibitors include KIT inhibition in combination with the VEGF inhibitor bevacizumab and a study of selective BCR-ABL kinase inhibitor nilotinib in imatinib-resistant melanoma. In the former phase 1/2 study, Flaherty and colleagues studied imatinib 800 mg daily and bevacizumab at 10 mg/kg every 2 weeks in 63 patients with advanced tumors, including 23 with metastatic melanoma. Although the combination was relatively nontoxic, no significant efficacy signal was seen and further accrual to the phase 2 portion was halted after the first stage was completed.⁸⁶ Nilotinib is a BCR-ABL1 tyrosine kinase inhibitor intelligently designed based on the structure of the ABL-imatinib complex that is 10 to 30 times more potent than imatinib in inhibiting BCR-ABL1 tyrosine kinase activity. Nilotinib is approved for the treatment of imatinib-resistant chronic myelogenous leukemia (CML), with reported efficacy in patients with central nervous system (CNS) involvement.^87,88 Nilotinib has been studied in a single study of KIT-mutated/amplified melanoma that included patients with imatinib-resistance and those with treated CNS disease. Nilotinib appeared to be active in imatinib-resistant melanoma, although no responses were seen in the CNS disease cohort.⁸⁹ Overall, the response rates observed with KIT inhibition in melanoma are much lower than those observed in CML and GIST.

CONCLUSION AND FUTURE DIRECTIONS

Prior to 2011, the only approved agents for the treatment of advanced melanoma were dacarbazine and high-dose interleukin-2. Since 2011, drug approvals in melanoma have proceeded at a frenetic pace unmatched in any other disease. The primary events underlying this are advances in our understanding of the gene mutation landscape driving melanoma tumorigenesis, accompanied by insights into the means by which tumors circumvent the induction of effective anti-tumor T-cell responses. These insights have resulted in the development of inhibitors targeting MAPK pathway kinases BRAF, MEK, and NRAS), KIT, and regulatory immune checkpoints (CTLA-4 and PD-1). Although BRAF/MEK inhibition results in profound reductions and even occasional complete responses in patients, these responses are typically short lived, rarely lasting more than 9 to 11 months; the encorafenib/binimetinib combination may improve that duration marginally. However, the signature therapeutic advance in melanoma of the past decade is immunotherapy, particularly the development of inhibitors of CTLA-4 and PD-1 immune checkpoints. With these agents, significant proportions of treated patients remain free of progression off-therapy (ipilimumab 23%; nivolumab 34%; pembrolizumab 35%; ipilimumab/nivolumab 64%), and some patients can be successfully re-induced after delayed progression. Separately, the high response rates observed with the use of KIT inhibitors in CML and GIST have not been observed in KIT mutated/amplified melanoma and development of agents in this space has been limited. The challenges ahead center around identifying predictive biomarkers and circumventing primary or acquired resistance, with the eventual goal of producing durable remissions in the majority of treated patients.

Our improved understanding of the mechanisms of acquired resistance to BRAF/MEK inhibitors suggests that anti-tumor activity may be achieved by targeting multiple pathways, possibly with combination regimens comprising other inhibitors and/or immunotherapy. Preclinical data supports the use of combination strategies targeting both ERK and PI3K/mTOR to circumvent acquired resistance.⁹⁰ Ongoing studies are evaluating combinations with biguanides (metformin: NCT02143050 and NCT01638676; phenformin: NCT03026517), HSP90 inhibitors (XL888: NCT02721459; AT13387: NCT02097225), and decitabine (NCT01876641).

One complexity affecting management of resistance in the targeted therapy landscape remains tumor heterogeneity, particularly intra- and intertumoral heterogeneity, which may explain the apparent contradiction between continued efficacy of BRAF inhibitors in BRAF-resistant tumors and preclinical data predicting slower progression of resistant tumors on cessation of BRAF inhibitors.^91–94 These data provide a rationale to investigate intermittent dosing regimens with BRAF/MEK inhibitors; several studies exploring this approach are ongoing (NCT01894672 and NCT02583516).

Given the specificity, adaptability, and memory response associated with immunotherapy, it is likely that these agents will be used to treat the majority of patients regardless of mutational status. Hence, identifying predictive biomarkers of response to immune checkpoint inhibitors is vital. The presence of CD8+ T-cell infiltrate and IFN-γ gene signature, which indicate an “inflamed” tumor microenvironment, are highly predictive of clinical benefit from PD-1 inhibitors.^95,96 However, not all PD-1 responders have “inflamed” tumor microenvironments, and not all patients with an “inflamed” tumor microenvironment respond to immune checkpoint inhibitors. The complexity of the immune system is reflected in the multiple non-redundant immunologic pathways, both positive and negative, with checkpoints and ligands that emerge dynamically in response to treatment. Given the dynamic nature of the immune response, it is unlikely that any single immunologic biomarker identified pre-treatment will be completely predictive. Rather, the complexity of the biomarker approach must match the complexity of the immune response elicited, and will likely incorporate multifarious elements including CD8+ T-cell infiltrate, IFN-γ gene signature, and additional elements including microbiome, genetic polymorphisms, and tumor mutation load. The goal is to use multiple markers to guide development of combinations and then, depending on initial response, to examine tumors for alterations to guide decisions about additional treatment(s) to improve responses, with the eventual goal being durable clinical responses for all patients.

INTRODUCTION

Colorectal cancer (CRC) is one of the most prevalent malignancies and is the fourth most common cancer in the United States, with an estimated 133,490 new cases diagnosed in 2016. Of these, approximately 95,520 are located in the colon and 39,970 are in the rectum.¹ CRC is the third leading cause of cancer death in women and the second leading cause of cancer death in men, with an estimated 49,190 total deaths in 2016.² The incidence appears to be increasing,³ especially in patients younger than 55 years of age;⁴ the reason for this increase remains uncertain.

A number of risk factors for the development of CRC have been identified. Numerous hered-itary CRC syndromes have been described, including familial adenomatous polyposis,⁵ hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome,⁶ and MUTYH-associated polyposis.^7,8 A family history of CRC doubles the risk of developing CRC,⁹ and current guidelines support lowering the age of screening in individuals with a family history of CRC to 10 years younger than the age of diagnosis of the family member or 40 years of age, whichever is lower.¹⁰ Patients with a personal history of adenomatous polyps are at increased risk for developing CRC, as are patients with a personal history of CRC, with a relative risk ranging from 3 to 6.¹¹ Ulcerative colitis and Crohn’s disease are associated with the development of CRC and also influence screening, though evidence suggests good control of these diseases may mitigate risk.¹² Finally, modifiable risk factors for the development of CRC include high red meat consumption,¹³ diets low in fiber,¹⁴ obesity,¹³ smoking, alcohol use,¹⁵ and physical inactivity¹⁶; lifestyle modification targeting these factors has been shown to decrease rates of CRC.¹⁷ The majority of colon cancers present with clinical symptoms, often with rectal bleeding, abdominal pain, change in bowel habits, or obstructive symptoms. More rarely, these tumors are detected during screening colonoscopy, in which case they tend to be at an early stage.

SURGICAL MANAGEMENT

A critical goal in the resection of early-stage colon cancer is attaining R0 resection. Patients who achieve R0 resection as compared to R1 (microscopic residual tumor) and R2 (macroscopic residual tumor)¹⁸ have significantly improved long-term overall survival.¹⁹ Traditionally, open resection of the involved colonic segment was employed, with end-end anastomosis of the uninvolved free margins. Laparoscopic resection for early-stage disease has been utilized in attempts to decrease morbidity of open procedures, with similar outcomes and node sampling.²⁰ Laparoscopic resection appears to provide similar outcomes even in locally advanced disease.²¹ Right-sided lesions are treated with right colectomy and primary ileocolic anastomosis.²² For patients presenting with obstructing masses, the Hartmann procedure is the most commonly performed operation. This involves creation of an ostomy with subtotal colectomy and subsequent ostomy reversal in a 2- or 3-stage protocol.²³ Patients with locally advanced disease and invasion into surrounding structures require multivisceral resection, which involves resection en bloc with secondarily involved organs.²⁴ Intestinal perforation presents a unique challenge and is associated with surgical complications, infection, and lower overall survival (OS) and 5-year disease-free survival (DFS). Complete mesocolic excision is a newer technique that has been performed with reports of better oncologic outcome at some centers; however, this approach is not currently considered standard of care.²⁵

STAGING

According to a report by the National Cancer Institute, the estimated 5-year relative survival rates for localized colon cancer (lymph node negative), regional (lymph node positive) disease, and distant (metastatic) disease are 89.9%, 71.3%, and 13.9%, respectively.¹ However, efforts have been made to further classify patients into distinct categories to allow fine-tuning of prognostication. In the current system, staging of colon cancer utilizes the American Joint Committee on Cancer tumor/node/metastasis (TNM) system.²⁰ Clinical and pathologic features include depth of invasion, local invasion of other organs, nodal involvement, and presence of distant metastasis (Table 1). Studies completed prior to the adoption of the TNM system used the Dukes criteria, which divided colon cancer into A, B, and C, corresponding to TNM stage I, stage IIA–IIC, and stage IIIA-IIIC. This classification is rarely used in more contemporary studies.

Adjuvant chemotherapy seeks to eliminate micrometastatic disease present following curative surgical resection. When stage 0 cancer is discovered incidentally during colonoscopy, endoscopic resection alone is the management of choice, as presence of micrometastatic disease is exceedingly unlikely.²⁶ Stage I–III CRCs are treated with surgical resection withcurative intent. The 5-year survival rate for stage I and early-stage II CRC is estimated at 97% with surgery alone.^27,28 The survival rate drops to about 60% for high-risk stage II tumors (T4aN0), and down to 50% or less for stage II-T4N0 or stage III cancers. Adjuvant chemotherapy is generally recommended to further decrease the rates of distant recurrence in certain cases of stage II and in all stage III tumors.

DETERMINATION OF BENEFIT FROM CHEMOTHERAPY: PROGNOSTIC MARKERS

Prior to administration of adjuvant chemotherapy, a clinical evaluation by the medical oncologist to determine appropriateness and safety of treatment is paramount. Poor performance status and comorbid conditions may indicate risk for excessive toxicity and minimal benefit from chemotherapy. CRC commonly presents in older individuals, with the median age at diagnosis of 69 years for men and 73 years for women.²⁹ In this patient population, comorbidities such as cardiovascular disease, diabetes, and renal dysfunction are more prevalent.³⁰ Decisions regarding adjuvant chemotherapy in this patient population have to take into consideration the fact that older patients may experience higher rates of toxicity with chemotherapy, including gastrointestinal toxicities and marrow suppression.³¹ Though some reports indicate patients older than 70 years derive similar benefit from adjuvant chemotherapy,^32,33 a large pooled analysis of the ACCENT database, which included 7 adjuvant therapy trials and 14,528 patients, suggested limited benefit from the addition of oxaliplatin to fluorouracil in elderly patients.³² Other factors that weigh on the decision include stage, pathology, and presence of high-risk features. A common concern in the postoperative setting is delaying initiation of chemotherapy to allow adequate wound healing; however, evidence suggests that delays longer than 8 weeks leads to worse overall survival, with hazard ratios (HR) ranging from 1.4 to 1.7.^34,35 Thus, the start of adjuvant therapy should ideally be within this time frame.

HIGH-RISK FEATURES

Multiple factors have been found to predict worse outcome and are classified as high-risk features (Table 2). Histologically, high-grade or poorly differentiated tumors are associated with higher recurrence rate and worse outcome.³⁶ Certain histological subtypes, including mucinous and signet-ring, both appear to have more aggressive biology.³⁷ Presence of microscopic invasion into surrounding blood vessels (vascular invasion) and nerves (perineural invasion) is associated with lower survival.³⁸ Penetration of the cancer through the visceral peritoneum (T4a) or into surrounding structures (T4b) is associated with lower survival.³⁶ During surgical resection, multiple lymph nodes are removed along with the primary tumor to evaluate for metastasis to the regional nodes. Multiple analyses have demonstrated that removal and pathologic assessment of fewer than 12 lymph nodes is associated with high risk of missing a positive node, and is thus equated with high risk.^39–41 In addition, extension of tumor beyond the capsules of any single lymph node, termed extracapsular extension, is associated with an increased risk of all-cause mortality.⁴² Tumor deposits, or focal aggregates of adenocarcinoma in the pericolic fat that are not contiguous with the primary tumor and are not associated with lymph nodes, are currently classified as lymph nodes as N1c in the current TNM staging system. Presence of these deposits has been found to predict poor outcome stage for stage.⁴³ Obstruction and/or perforation secondary to the tumor are also considered high-risk features that predict poor outcome.

SIDEDNESS

As reported at the 2016 American Society of Clinical Oncology annual meeting, tumor location predicts outcome in the metastatic setting. A report by Venook and colleagues based on a post-hoc analysis found that in the metastatic setting, location of the tumor primary in the left side is associated with longer OS (33.3 months) when compared to the right side of the colon (19.4 months).⁴⁴ A retrospective analysis of multiple databases presented by Schrag and colleagues similarly reported inferior outcomes in patients with stage III and IV disease who had right-sided primary tumors.⁴⁵ However, the prognostic implications for stage II disease remain uncertain.

BIOMARKERS

Given the controversy regarding adjuvant therapy of patients with stage II colon cancer, multiple biomarkers have been evaluated as possible predictive markers that can assist in this decision. The mismatch repair (MMR) system is a complex cellular enzymatic mechanism that identifies and corrects DNA errors during cell division and prevents mutagenesis.⁴⁶ The familial cancer syndrome HNPCC is linked to alteration in a variety of MMR genes, leading to deficient mismatch repair (dMMR), also termed microsatellite instability-high (MSI-high).^47,48 Epigenetic modification can also lead to silencing of the same implicated genes and accounts for 15% to 20% of sporadic colorectal cancer.⁴⁹ These epigenetic modifications lead to hypermethylation of the promotor region of MLH1 in 70% of cases.⁵⁰ The 4 MMR genes most commonly tested are MLH-1, MSH2, MSH6, and PMS2. Testing can be performed by immunohistochemistry or polymerase chain reaction.⁵¹ Across tumor histology and stage, MSI status is prognostic. Patients with MSI-high tumors have been shown to have improved prognosis and longer OS both in stage II and III disease^52–54 and in the metastatic setting.⁵⁵ However, despite this survival benefit, there is conflicting data as to whether patients with stage II, MSI-high colon cancer may benefit less from adjuvant chemotherapy. One early retrospective study compared outcomes of 70 patients with stage II and III disease and dMMR to those of 387 patients with stage II and III disease and proficient mismatch repair (pMMR). Adjuvant fluorouracil with leucovorin improved DFS for patients with pMMR (HR 0.67) but not for those with dMMR (HR 1.10). In addition, for patients with stage II disease and dMMR, the HR for OS was inferior at 2.95.⁵⁶ Data collected from randomized clinical trials using fluorouracil-based adjuvant chemotherapy were analyzed in an attempt to predict benefit based on MSI status. Benefit was only seen in pMMR patients, with a HR of 0.72; this was not seen in the dMMR patients.⁵⁷ Subsequent studies have had different findings and did not demonstrate a detrimental effect of fluorouracil in dMMR.^58,59 For stage III patients, MSI status does not appear to affect benefit from chemotherapy, as analysis of data from the NSABP C-07 trial (Table 3) demonstrated benefit of FOLFOX (leucovorin, fluorouracil, oxaliplatin) in patients with dMMR status and stage III disease.⁵⁹

Another genetic abnormality identified in colon cancers is chromosome 18q loss of heterozygosity (LOH). The presence of 18q LOH appears to be inversely associated with MSI-high status. Some reports have linked presence of 18q with worse outcome,⁶⁰ but others question this, arguing the finding may simply be related to MSI status.^61,62 This biomarker has not been established as a clear prognostic marker that can aid clinical decisions.

Most recently, expression of caudal-type homeobox transcription factor 2 (CDX2) has been reported as a novel prognostic and predictive tool. A 2015 report linked lack of expression of CDX2 to worse outcome; in this study, 5-year DFS was 41% in patients with CDX2-negative tumors versus 74% in the CDX2-positive tumors, with a HR of disease recurrence of 2.73 for CDX2-negative tumors.⁶³ Similar numbers were observed in patients with stage II disease, with 5-year OS of 40% in patients with CDX2-negative tumors versus 70% in those with CDX2-positive tumors. Treatment of CDX2-negative patients with adjuvant chemotherapy improved outcomes: 5-year DFS in the stage II subgroup was 91% with chemotherapy versus 56% without, and in the stage III subgroup, 74% with chemotherapy versus 37% without. The authors concluded that patients with stage II and III colon cancer that is CDX2-negative may benefit from adjuvant chemotherapy. Importantly, CDX2-negativity is a rare event, occurring in only 6.9% of evaluable tumors.

RISK ASSESSMENT TOOLS

Several risk assessment tools have been developed in an attempt to aid clinical decision making regarding adjuvant chemotherapy for patients with stage II colon cancer. The Oncotype DX Colon Assay analyses a 12-gene signature in the pathologic sample and was developed with the goal to improve prognostication and aid in treatment decision making. The test utilizes reverse transcription-PCR on RNA extracted from the tumor.⁶⁴ After evaluating 12 genes, a recurrence score is generated that predicts the risk of disease recurrence. This score was validated using data from 3 large clinical trials.^65–67 Unlike the Oncotype Dx score used in breast cancer, the test in colon cancer has not been found to predict the benefit from chemotherapy and has not been incorporated widely into clinical practice.

Adjuvant! Online (available at www.adjuvantonline.com) is a web-based tool that combines clinical and histological features to estimate outcome. Calculations are based on US SEER tumor registry-reported outcomes.⁶⁸ A second web-based tool, Numeracy (available at www.mayoclinic.com/calcs), was developed by the Mayo Clinic using pooled data from 7 randomized clinical trials including 3341 patients.⁶⁸ Both tools seek to predict absolute benefit for patients treated with fluorouracil, though data suggests Adjuvant! Online may be more reliable in its predictive ability.⁶⁹ Adjuvant! Online has also been validated in an Asian population70 and patients older than 70 years.⁷¹

MUTATIONAL ANALYSIS

Multiple mutations in proto-oncogenes have been found in colon cancer cells. One such proto-oncogene is BRAF, which encodes a serine-threonine kinase in the rapidly accelerated fibrosarcoma (RAF). Mutations in BRAF have been found in 5% to 10% of colon cancers and are associated with right-sided tumors.⁷² As a prognostic marker, some studies have associated BRAF mutations with worse prognosis, including shorter time to relapse and shorter OS.^73,74 Two other proto-oncogenes are Kristen rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma rat sarcoma viral oncogene homolog (NRAS), both of which encode proteins downstream of epidermal growth factor receptor (EGFR). KRAS and NRAS mutations have been shown to be predictive in the metastatic setting where they predict resistance to the EGFR inhibitors cetuximab and panitumumab.^75,76 The effect of KRAS and NRAS mutations on outcome in stage II and III colon cancer is uncertain. Some studies suggest worse outcome in KRAS-mutated cancers,⁷⁷ while others failed to demonstrate this finding.⁷³

CASE PRESENTATION 1

A 53-year-old man with no past medical history presents to the emergency department with early satiety and generalized abdominal pain. Laboratory evaluation shows a microcytic anemia with normal white blood cell count, platelet count, renal function, and liver function tests. Computed tomography (CT) scan of the abdomen and pelvis show a 4-cm mass in the transverse colon without obstruction and without abnormality in the liver. CT scan of the chest does not demonstrate pathologic lymphadenopathy or other findings. He undergoes robotic laparoscopic transverse colon resection and appendectomy. Pathology confirms a 3.5-cm focus of adenocarcinoma of the colon with invasion through the muscularis propria and 5 of 27 regional lymph nodes positive for adenocarcinoma and uninvolved proximal, distal, and radial margins. He is given a stage of IIIB pT3 pN2a M0 and referred to medical oncology for further management, where 6 months of adjuvant FOLFOX chemotherapy is recommended.

ADJUVANT CHEMOTHERAPY IN STAGE III COLON CANCER

Postoperative adjuvant chemotherapy is the standard of care for patients with stage III disease. In the 1960s, infusional fluorouracil was first used to treat inoperable colon cancer.^78,79 After encouraging results, the agent was used both intraluminally and intravenously as an adjuvant therapy for patients undergoing resection with curative intent; however, only modest benefits were described.^80,81 The National Surgical Adjuvant Breast and Bowel Project (NSABP) C-01 trial (Table 3) was the first study to demonstrate a benefit from adjuvant chemotherapy in colon cancer. This study randomly assigned patients with stage II and III colon cancer to surgery alone, postoperative chemotherapy with fluorouracil, semustine, and vincristine (MOF), or postoperative bacillus Calmette-Guérin (BCG). DFS and OS were significantly improved with MOF chemotherapy.⁸² In 1990, a landmark study reported on outcomes after treatment of 1296 patients with stage III colon cancer with adjuvant fluorouracil and levamisole for 12 months. The combination was associated with a 41% reduction in risk of cancer recurrence and a 33% reduction in risk of death.⁸³ The NSABP C-03 trial (Table 3) compared MOF to the combination of fluorouracil and leucovorin and demonstrated improved 3-year DFS (69% versus 73%) and 3-year OS (77% versus 84%) in patients with stage III disease.⁸⁴ Building on these outcomes, the QUASAR study (Table 3) compared fluorouracil in combination with one of levamisole, low-dose leucovorin, or high-dose leucovorin. The study enrolled 4927 patients and found worse outcomes with fluorouracil plus levamisole and no difference in low-doseversus high-dose leucovorin.⁸⁵ Levamisole fell out of use after associations with development of multifocal leukoencephalopathy,⁸⁶ and was later shown to have inferior outcomes versus leucovorin when combined with fluorouracil.^87,88 Intravenous fluorouracil has shown similar benefit when administered by bolus or infusion,⁸⁹ although continuous infusion has been associated with lower incidence of severe toxicity.⁹⁰ The efficacy of the oral fluoropyrimidine capecitabine has been shown to be equivalent to that of fluorouracil.⁹¹

Fluorouracil-based treatment remained the standard of care until the introduction of oxaliplatin in the mid-1990s. After encouraging results in the metastatic setting,^92,93 the agent was moved to the adjuvant setting. The MOSAIC trial (Table 3) randomly assigned patients with stage II and III colon cancer to fluorouracil with leucovorin (FULV) versus FOLFOX given once every 2 weeks for 12 cycles. Analysis with respect to stage III patients showed a clear survival benefit, with a 10-year OS of 67.1% with FOLFOX chemotherapy versus 59% with fluorouracil and leucovorin.^94,95 The NSABP C-07 (Table 3) trial used a similar trial design but employed bolus fluorouracil. More than 2400 patients with stage II and III colon cancer were randomly assigned to bolus FULV or bolus fluorouracil, leucovorin, and oxaliplatin (FLOX). The addition of oxaliplatin significantly improved outcomes, with 4-year DFS of 67% versus 71.8% for FULV and FLOX, respectively, and a HR of death of 0.80 with FLOX.^59,96 The multicenter N016968 trial (Table 3) randomly assigned 1886 patients with stage III colon cancer to adjuvant capecitabine plus oxaliplatin (XELOX) or bolus fluorouracil plus leucovorin (FU/FA). The 3-year DFS was 70.9% versus 66.5% with XELOX and FU/FA, respectively, and 5-year OS was 77.6% versus 74.2%, respectively.^97,98

In the metastatic setting, additional agents have shown efficacy, including irinotecan,^99,100 bevacizumab,^101,102 cetuximab,^103,104 and regorafenib.¹⁰⁵ This observation led to testing of these agents in earlier stage disease. The CALGB 89803 trial compared fluorouracil, leucovorin, and irinotecan to fluorouracil with leucovorin alone. No benefit in 5-year DFS or OS was seen.¹⁰⁶ Similarly, infusional fluorouracil, leucovorin, and irinotecan (FOLFIRI) was not found to improve 5-year DFS as compared to fluorouracil with leucovorin alone in the PETACC-3 trial.¹⁰⁷ The NSABP C-08 trial considered the addition of bevacizumab to FOLFOX. When compared to FOLFOX alone, the combination of bevacizumab to FOLFOX had similar 3-year DFS (77.9% versus 75.1%) and 5-year OS (82.5% versus 80.7%).¹⁰⁸ This finding was confirmed in the Avant trial.¹⁰⁹ The addition of cetuximab to FOLFOX was equally disappointing, as shown in the N0147 trial110 and PETACC-8 trial.¹¹¹ Data on regorafenib in the adjuvant setting for stage III colon cancer is lacking; however, 2 ongoing clinical trials, NCT02425683 and NCT02664077, are each studying the use of regorafenib following completion of FOLFOX for patients with stage III disease.

Thus, after multiple trials comparing various regimens and despite attempts to improve outcomes by the addition of a third agent, the standard of care per National Comprehensive Cancer Network (NCCN) guidelines for management of stage III colon cancer remains 12 cycles of FOLFOX chemotherapy. Therapy should be initiated within 8 weeks of surgery. Data are emerging to support a short duration of therapy for patients with low-risk stage III tumors, as shown in an abstract presented at the 2017 American Society of Clinical Oncology annual meeting. The IDEA trial was a pooled analysis of 6 randomized clinical trials across multiple countries, all of which evaluated 3 versus 6 months of FOLFOX or capecitabine and oxaliplatin in the treatment of stage III colon cancer. The analysis was designed to test non-inferiority of 3 months of therapy as compared to 6 months. The analysis included 6088 patients across 244 centers in 6 countries. The overall analysis failed to establish noninferiority. The 3-year DFS rate was 74.6% for 3 months and 75.5% for 6 months, with a DFS HR of 1.07 and a confidence interval that did not meet the prespecified endpoint. Subgroup analysis suggested noninferiority for lower stage disease (T1–3 or N1) but not for higher stage disease (T4 or N2). Given the high rates of neuropathy with 6 months of oxaliplatin, these results suggest that 3 months of adjuvant therapy can be considered for patients with T1–3 or N1 disease in an attempt to limit toxicity.¹¹²

CASE PRESENTATION 2

A 57-year-old woman presents to the emergency department with fever and abdominal pain. CT of the abdomen and pelvis demonstrates a left-sided colonic mass with surrounding fat stranding and pelvic abscess. She is taken emergently for left hemicolectomy, cholecystectomy, and evacuation of pelvic abscess. Pathology reveals a 5-cm adenocarcinoma with invasion through the visceral peritoneum; 0/22 lymph nodes are involved. She is given a diagnosis of stage IIC and referred to medical oncology for further management. Due to her young age and presence of high-risk features, she is recommended adjuvant therapy with FOLFOX for 6 months.

ADJUVANT CHEMOTHERAPY IN STAGE II COLON CANCER

Because of excellent outcomes with surgical resection alone for stage II cancers, the use of adjuvant chemotherapy for patients with stage II disease is controversial. Limited prospective data is available to guide adjuvant treatment decisions for stage II patients. The QUASAR trial, which compared observation to adjuvant fluorouracil and leucovorin in patients with early-stage colon cancer, included 2963 patients with stage II disease and found a relative risk (RR) of death or recurrence of 0.82 and 0.78, respectively. Importantly, the absolute benefit of therapy was less than 5%.¹¹³ The IMPACT-B2 trial (Table 3) combined data from 5 separate trials and analyzed 1016 patients with stage II colon cancer who received fluorouracil with leucovorin or observation. Event-free survival was 0.86 versus 0.83 and 5-year OS was 82% versus 80%, suggesting no benefit.¹¹⁴ The benefit of addition of oxaliplatin to fluorouracil in stage II disease appears to be less than the benefit of adding this agent in the treatment of stage III CRC. As noted above, the MOSAIC trial randomly assigned patients with stage II and III colon cancer to receive adjuvant fluorouracil and leucovorin with or without oxaliplatin for 12 cycles. After a median follow-up of 9.5 years, 10-year OS rates for patients with stage II disease were 78.4% versus 79.5%. For patients with high-risk stage II disease (defined as T4, bowel perforation, or fewer than 10 lymph nodes examined), 10-year OS was 71.7% and 75.4% respectively, but these differences were not statistically significant.⁹⁴

Because of conflicting data as to the benefit of adding oxaliplatin in stage II disease, oxaliplatin is not recommended for standard-risk stage II patients. The use of oxaliplatin in high-risk stage II tumors should be weighed carefully given the toxicity risk. Oxaliplatin is recognized to cause sensory neuropathy in many patients, which can become painful and debilitating.¹¹⁵ Two types of neuropathy are associated with oxaliplatin: acute and chronic. Acute neuropathy manifests most often as cold-induced paresthesias in the fingers and toes and is quite common, affecting up to 90% of patients. These symptoms are self-limited and resolve usually within 1 week of each treatment.¹¹⁶ Some patients, with reports ranging from 10% to 79%, develop chronic neuropathy that persists for 1 year or more and causes significant decrements in quality of life.¹¹⁷ Patients older than age 70 may be at greater risk for oxaliplatin-induced neuropathy, which would increase risk of falls in this population.¹¹⁸ In addition to neuropathy, oxaliplatin is associated with hypersensitivity reactions that can be severe and even fatal.¹¹⁹ In a single institution series, the incidence of severe reactions was 2%.¹²⁰ Desensitization following hypersensitivity reactions is possible but requires a time-intensive protocol.¹²¹

Based on the inconclusive efficacy findings and due to concerns over toxicity, each decision must be individualized to fit patient characteristics and preferences. In general, for patients with stage II disease without high-risk features, an individualized discussion should be held as to the risks and benefits of single-agent fluorouracil, and this treatment should be offered in cases where the patient or provider would like to be aggressive. Patients with stage II cancer who have 1 or more high-risk features are often recommended adjuvant chemotherapy. Whether treatment with fluorouracil plus leucovorin or FOLFOX is preferred remains uncertain, and thus the risks and the potential gains of oxaliplatin must be discussed with the individual patient. MMR status can also influence the treatment recommendation for patients with stage II disease. In general, patients with standard-risk stage II tumors that are pMMR are offered MMR with leucovorin or oral capecitabine for 12 cycles. FOLFOX is considered for patients with MSI-high disease and those with multiple high-risk features.

MONITORING AFTER THERAPY

After completion of adjuvant chemotherapy, patients enter a period of survivorship. Patients are seen in clinic for symptom and laboratory monitoring of the complete blood count, liver function tests, and carcinoembryonic antigen (CEA). NCCN guidelines support history and physical examination with CEA testing every 3 to 6 months for the first 2 years, then every 6 months for the next 3 years, after which many patients continue to be seen annually. CT imaging of the chest, abdomen, and pelvis for monitoring of disease recurrence is recommended every 6 to 12 months for a total of 5 years. New elevations in CEA or liver function tests should prompt early imaging. Colonoscopy should be performed 1 year after completion of therapy; however, if no preoperative colonoscopy was performed, this should be done 3 to 6 months after completion. Colonoscopy is then repeated in 3 years and then every 5 years unless advanced adenomas are present.¹²²

SUMMARY

The addition of chemotherapy to surgical management of colon cancer has lowered the rate of disease recurrence and improved long-term survival. Adjuvant FOLFOX for 12 cycles is the standard of care for patients with stage III colon cancer and for patients with stage II disease with certain high-risk features. Use of adjuvant chemotherapy in stage II disease without high-risk features is controversial, and treatment decisions should be individualized. Biologic markers such as MSI and CDX2 status as well as patient-related factors including age, overall health, and personal preferences can inform treatment decisions. If chemotherapy is recommended in this setting, it would be with single-agent fluorouracil in an infusional or oral formulation, unless the tumor has the MSI-high feature. Following completion of adjuvant therapy, patients should be followed with clinical evaluation, laboratory testing, and imaging for a total of 5 years as per recommended guidelines.

INTRODUCTION

Colorectal cancer (CRC) is one of the most prevalent malignancies and is the fourth most common cancer in the United States, with an estimated 133,490 new cases diagnosed in 2016. Of these, approximately 95,520 are located in the colon and 39,970 are in the rectum.¹ CRC is the third leading cause of cancer death in women and the second leading cause of cancer death in men, with an estimated 49,190 total deaths in 2016.² The incidence appears to be increasing,³ especially in patients younger than 55 years of age;⁴ the reason for this increase remains uncertain.

A number of risk factors for the development of CRC have been identified. Numerous hered-itary CRC syndromes have been described, including familial adenomatous polyposis,⁵ hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome,⁶ and MUTYH-associated polyposis.^7,8 A family history of CRC doubles the risk of developing CRC,⁹ and current guidelines support lowering the age of screening in individuals with a family history of CRC to 10 years younger than the age of diagnosis of the family member or 40 years of age, whichever is lower.¹⁰ Patients with a personal history of adenomatous polyps are at increased risk for developing CRC, as are patients with a personal history of CRC, with a relative risk ranging from 3 to 6.¹¹ Ulcerative colitis and Crohn’s disease are associated with the development of CRC and also influence screening, though evidence suggests good control of these diseases may mitigate risk.¹² Finally, modifiable risk factors for the development of CRC include high red meat consumption,¹³ diets low in fiber,¹⁴ obesity,¹³ smoking, alcohol use,¹⁵ and physical inactivity¹⁶; lifestyle modification targeting these factors has been shown to decrease rates of CRC.¹⁷ The majority of colon cancers present with clinical symptoms, often with rectal bleeding, abdominal pain, change in bowel habits, or obstructive symptoms. More rarely, these tumors are detected during screening colonoscopy, in which case they tend to be at an early stage.

SURGICAL MANAGEMENT

A critical goal in the resection of early-stage colon cancer is attaining R0 resection. Patients who achieve R0 resection as compared to R1 (microscopic residual tumor) and R2 (macroscopic residual tumor)¹⁸ have significantly improved long-term overall survival.¹⁹ Traditionally, open resection of the involved colonic segment was employed, with end-end anastomosis of the uninvolved free margins. Laparoscopic resection for early-stage disease has been utilized in attempts to decrease morbidity of open procedures, with similar outcomes and node sampling.²⁰ Laparoscopic resection appears to provide similar outcomes even in locally advanced disease.²¹ Right-sided lesions are treated with right colectomy and primary ileocolic anastomosis.²² For patients presenting with obstructing masses, the Hartmann procedure is the most commonly performed operation. This involves creation of an ostomy with subtotal colectomy and subsequent ostomy reversal in a 2- or 3-stage protocol.²³ Patients with locally advanced disease and invasion into surrounding structures require multivisceral resection, which involves resection en bloc with secondarily involved organs.²⁴ Intestinal perforation presents a unique challenge and is associated with surgical complications, infection, and lower overall survival (OS) and 5-year disease-free survival (DFS). Complete mesocolic excision is a newer technique that has been performed with reports of better oncologic outcome at some centers; however, this approach is not currently considered standard of care.²⁵

STAGING

According to a report by the National Cancer Institute, the estimated 5-year relative survival rates for localized colon cancer (lymph node negative), regional (lymph node positive) disease, and distant (metastatic) disease are 89.9%, 71.3%, and 13.9%, respectively.¹ However, efforts have been made to further classify patients into distinct categories to allow fine-tuning of prognostication. In the current system, staging of colon cancer utilizes the American Joint Committee on Cancer tumor/node/metastasis (TNM) system.²⁰ Clinical and pathologic features include depth of invasion, local invasion of other organs, nodal involvement, and presence of distant metastasis (Table 1). Studies completed prior to the adoption of the TNM system used the Dukes criteria, which divided colon cancer into A, B, and C, corresponding to TNM stage I, stage IIA–IIC, and stage IIIA-IIIC. This classification is rarely used in more contemporary studies.

Adjuvant chemotherapy seeks to eliminate micrometastatic disease present following curative surgical resection. When stage 0 cancer is discovered incidentally during colonoscopy, endoscopic resection alone is the management of choice, as presence of micrometastatic disease is exceedingly unlikely.²⁶ Stage I–III CRCs are treated with surgical resection withcurative intent. The 5-year survival rate for stage I and early-stage II CRC is estimated at 97% with surgery alone.^27,28 The survival rate drops to about 60% for high-risk stage II tumors (T4aN0), and down to 50% or less for stage II-T4N0 or stage III cancers. Adjuvant chemotherapy is generally recommended to further decrease the rates of distant recurrence in certain cases of stage II and in all stage III tumors.

DETERMINATION OF BENEFIT FROM CHEMOTHERAPY: PROGNOSTIC MARKERS

Prior to administration of adjuvant chemotherapy, a clinical evaluation by the medical oncologist to determine appropriateness and safety of treatment is paramount. Poor performance status and comorbid conditions may indicate risk for excessive toxicity and minimal benefit from chemotherapy. CRC commonly presents in older individuals, with the median age at diagnosis of 69 years for men and 73 years for women.²⁹ In this patient population, comorbidities such as cardiovascular disease, diabetes, and renal dysfunction are more prevalent.³⁰ Decisions regarding adjuvant chemotherapy in this patient population have to take into consideration the fact that older patients may experience higher rates of toxicity with chemotherapy, including gastrointestinal toxicities and marrow suppression.³¹ Though some reports indicate patients older than 70 years derive similar benefit from adjuvant chemotherapy,^32,33 a large pooled analysis of the ACCENT database, which included 7 adjuvant therapy trials and 14,528 patients, suggested limited benefit from the addition of oxaliplatin to fluorouracil in elderly patients.³² Other factors that weigh on the decision include stage, pathology, and presence of high-risk features. A common concern in the postoperative setting is delaying initiation of chemotherapy to allow adequate wound healing; however, evidence suggests that delays longer than 8 weeks leads to worse overall survival, with hazard ratios (HR) ranging from 1.4 to 1.7.^34,35 Thus, the start of adjuvant therapy should ideally be within this time frame.

HIGH-RISK FEATURES

Multiple factors have been found to predict worse outcome and are classified as high-risk features (Table 2). Histologically, high-grade or poorly differentiated tumors are associated with higher recurrence rate and worse outcome.³⁶ Certain histological subtypes, including mucinous and signet-ring, both appear to have more aggressive biology.³⁷ Presence of microscopic invasion into surrounding blood vessels (vascular invasion) and nerves (perineural invasion) is associated with lower survival.³⁸ Penetration of the cancer through the visceral peritoneum (T4a) or into surrounding structures (T4b) is associated with lower survival.³⁶ During surgical resection, multiple lymph nodes are removed along with the primary tumor to evaluate for metastasis to the regional nodes. Multiple analyses have demonstrated that removal and pathologic assessment of fewer than 12 lymph nodes is associated with high risk of missing a positive node, and is thus equated with high risk.^39–41 In addition, extension of tumor beyond the capsules of any single lymph node, termed extracapsular extension, is associated with an increased risk of all-cause mortality.⁴² Tumor deposits, or focal aggregates of adenocarcinoma in the pericolic fat that are not contiguous with the primary tumor and are not associated with lymph nodes, are currently classified as lymph nodes as N1c in the current TNM staging system. Presence of these deposits has been found to predict poor outcome stage for stage.⁴³ Obstruction and/or perforation secondary to the tumor are also considered high-risk features that predict poor outcome.

SIDEDNESS

As reported at the 2016 American Society of Clinical Oncology annual meeting, tumor location predicts outcome in the metastatic setting. A report by Venook and colleagues based on a post-hoc analysis found that in the metastatic setting, location of the tumor primary in the left side is associated with longer OS (33.3 months) when compared to the right side of the colon (19.4 months).⁴⁴ A retrospective analysis of multiple databases presented by Schrag and colleagues similarly reported inferior outcomes in patients with stage III and IV disease who had right-sided primary tumors.⁴⁵ However, the prognostic implications for stage II disease remain uncertain.

BIOMARKERS

Given the controversy regarding adjuvant therapy of patients with stage II colon cancer, multiple biomarkers have been evaluated as possible predictive markers that can assist in this decision. The mismatch repair (MMR) system is a complex cellular enzymatic mechanism that identifies and corrects DNA errors during cell division and prevents mutagenesis.⁴⁶ The familial cancer syndrome HNPCC is linked to alteration in a variety of MMR genes, leading to deficient mismatch repair (dMMR), also termed microsatellite instability-high (MSI-high).^47,48 Epigenetic modification can also lead to silencing of the same implicated genes and accounts for 15% to 20% of sporadic colorectal cancer.⁴⁹ These epigenetic modifications lead to hypermethylation of the promotor region of MLH1 in 70% of cases.⁵⁰ The 4 MMR genes most commonly tested are MLH-1, MSH2, MSH6, and PMS2. Testing can be performed by immunohistochemistry or polymerase chain reaction.⁵¹ Across tumor histology and stage, MSI status is prognostic. Patients with MSI-high tumors have been shown to have improved prognosis and longer OS both in stage II and III disease^52–54 and in the metastatic setting.⁵⁵ However, despite this survival benefit, there is conflicting data as to whether patients with stage II, MSI-high colon cancer may benefit less from adjuvant chemotherapy. One early retrospective study compared outcomes of 70 patients with stage II and III disease and dMMR to those of 387 patients with stage II and III disease and proficient mismatch repair (pMMR). Adjuvant fluorouracil with leucovorin improved DFS for patients with pMMR (HR 0.67) but not for those with dMMR (HR 1.10). In addition, for patients with stage II disease and dMMR, the HR for OS was inferior at 2.95.⁵⁶ Data collected from randomized clinical trials using fluorouracil-based adjuvant chemotherapy were analyzed in an attempt to predict benefit based on MSI status. Benefit was only seen in pMMR patients, with a HR of 0.72; this was not seen in the dMMR patients.⁵⁷ Subsequent studies have had different findings and did not demonstrate a detrimental effect of fluorouracil in dMMR.^58,59 For stage III patients, MSI status does not appear to affect benefit from chemotherapy, as analysis of data from the NSABP C-07 trial (Table 3) demonstrated benefit of FOLFOX (leucovorin, fluorouracil, oxaliplatin) in patients with dMMR status and stage III disease.⁵⁹

Another genetic abnormality identified in colon cancers is chromosome 18q loss of heterozygosity (LOH). The presence of 18q LOH appears to be inversely associated with MSI-high status. Some reports have linked presence of 18q with worse outcome,⁶⁰ but others question this, arguing the finding may simply be related to MSI status.^61,62 This biomarker has not been established as a clear prognostic marker that can aid clinical decisions.

Most recently, expression of caudal-type homeobox transcription factor 2 (CDX2) has been reported as a novel prognostic and predictive tool. A 2015 report linked lack of expression of CDX2 to worse outcome; in this study, 5-year DFS was 41% in patients with CDX2-negative tumors versus 74% in the CDX2-positive tumors, with a HR of disease recurrence of 2.73 for CDX2-negative tumors.⁶³ Similar numbers were observed in patients with stage II disease, with 5-year OS of 40% in patients with CDX2-negative tumors versus 70% in those with CDX2-positive tumors. Treatment of CDX2-negative patients with adjuvant chemotherapy improved outcomes: 5-year DFS in the stage II subgroup was 91% with chemotherapy versus 56% without, and in the stage III subgroup, 74% with chemotherapy versus 37% without. The authors concluded that patients with stage II and III colon cancer that is CDX2-negative may benefit from adjuvant chemotherapy. Importantly, CDX2-negativity is a rare event, occurring in only 6.9% of evaluable tumors.

RISK ASSESSMENT TOOLS

Several risk assessment tools have been developed in an attempt to aid clinical decision making regarding adjuvant chemotherapy for patients with stage II colon cancer. The Oncotype DX Colon Assay analyses a 12-gene signature in the pathologic sample and was developed with the goal to improve prognostication and aid in treatment decision making. The test utilizes reverse transcription-PCR on RNA extracted from the tumor.⁶⁴ After evaluating 12 genes, a recurrence score is generated that predicts the risk of disease recurrence. This score was validated using data from 3 large clinical trials.^65–67 Unlike the Oncotype Dx score used in breast cancer, the test in colon cancer has not been found to predict the benefit from chemotherapy and has not been incorporated widely into clinical practice.

Adjuvant! Online (available at www.adjuvantonline.com) is a web-based tool that combines clinical and histological features to estimate outcome. Calculations are based on US SEER tumor registry-reported outcomes.⁶⁸ A second web-based tool, Numeracy (available at www.mayoclinic.com/calcs), was developed by the Mayo Clinic using pooled data from 7 randomized clinical trials including 3341 patients.⁶⁸ Both tools seek to predict absolute benefit for patients treated with fluorouracil, though data suggests Adjuvant! Online may be more reliable in its predictive ability.⁶⁹ Adjuvant! Online has also been validated in an Asian population70 and patients older than 70 years.⁷¹

MUTATIONAL ANALYSIS

Multiple mutations in proto-oncogenes have been found in colon cancer cells. One such proto-oncogene is BRAF, which encodes a serine-threonine kinase in the rapidly accelerated fibrosarcoma (RAF). Mutations in BRAF have been found in 5% to 10% of colon cancers and are associated with right-sided tumors.⁷² As a prognostic marker, some studies have associated BRAF mutations with worse prognosis, including shorter time to relapse and shorter OS.^73,74 Two other proto-oncogenes are Kristen rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma rat sarcoma viral oncogene homolog (NRAS), both of which encode proteins downstream of epidermal growth factor receptor (EGFR). KRAS and NRAS mutations have been shown to be predictive in the metastatic setting where they predict resistance to the EGFR inhibitors cetuximab and panitumumab.^75,76 The effect of KRAS and NRAS mutations on outcome in stage II and III colon cancer is uncertain. Some studies suggest worse outcome in KRAS-mutated cancers,⁷⁷ while others failed to demonstrate this finding.⁷³

CASE PRESENTATION 1

A 53-year-old man with no past medical history presents to the emergency department with early satiety and generalized abdominal pain. Laboratory evaluation shows a microcytic anemia with normal white blood cell count, platelet count, renal function, and liver function tests. Computed tomography (CT) scan of the abdomen and pelvis show a 4-cm mass in the transverse colon without obstruction and without abnormality in the liver. CT scan of the chest does not demonstrate pathologic lymphadenopathy or other findings. He undergoes robotic laparoscopic transverse colon resection and appendectomy. Pathology confirms a 3.5-cm focus of adenocarcinoma of the colon with invasion through the muscularis propria and 5 of 27 regional lymph nodes positive for adenocarcinoma and uninvolved proximal, distal, and radial margins. He is given a stage of IIIB pT3 pN2a M0 and referred to medical oncology for further management, where 6 months of adjuvant FOLFOX chemotherapy is recommended.

ADJUVANT CHEMOTHERAPY IN STAGE III COLON CANCER

Postoperative adjuvant chemotherapy is the standard of care for patients with stage III disease. In the 1960s, infusional fluorouracil was first used to treat inoperable colon cancer.^78,79 After encouraging results, the agent was used both intraluminally and intravenously as an adjuvant therapy for patients undergoing resection with curative intent; however, only modest benefits were described.^80,81 The National Surgical Adjuvant Breast and Bowel Project (NSABP) C-01 trial (Table 3) was the first study to demonstrate a benefit from adjuvant chemotherapy in colon cancer. This study randomly assigned patients with stage II and III colon cancer to surgery alone, postoperative chemotherapy with fluorouracil, semustine, and vincristine (MOF), or postoperative bacillus Calmette-Guérin (BCG). DFS and OS were significantly improved with MOF chemotherapy.⁸² In 1990, a landmark study reported on outcomes after treatment of 1296 patients with stage III colon cancer with adjuvant fluorouracil and levamisole for 12 months. The combination was associated with a 41% reduction in risk of cancer recurrence and a 33% reduction in risk of death.⁸³ The NSABP C-03 trial (Table 3) compared MOF to the combination of fluorouracil and leucovorin and demonstrated improved 3-year DFS (69% versus 73%) and 3-year OS (77% versus 84%) in patients with stage III disease.⁸⁴ Building on these outcomes, the QUASAR study (Table 3) compared fluorouracil in combination with one of levamisole, low-dose leucovorin, or high-dose leucovorin. The study enrolled 4927 patients and found worse outcomes with fluorouracil plus levamisole and no difference in low-doseversus high-dose leucovorin.⁸⁵ Levamisole fell out of use after associations with development of multifocal leukoencephalopathy,⁸⁶ and was later shown to have inferior outcomes versus leucovorin when combined with fluorouracil.^87,88 Intravenous fluorouracil has shown similar benefit when administered by bolus or infusion,⁸⁹ although continuous infusion has been associated with lower incidence of severe toxicity.⁹⁰ The efficacy of the oral fluoropyrimidine capecitabine has been shown to be equivalent to that of fluorouracil.⁹¹

Fluorouracil-based treatment remained the standard of care until the introduction of oxaliplatin in the mid-1990s. After encouraging results in the metastatic setting,^92,93 the agent was moved to the adjuvant setting. The MOSAIC trial (Table 3) randomly assigned patients with stage II and III colon cancer to fluorouracil with leucovorin (FULV) versus FOLFOX given once every 2 weeks for 12 cycles. Analysis with respect to stage III patients showed a clear survival benefit, with a 10-year OS of 67.1% with FOLFOX chemotherapy versus 59% with fluorouracil and leucovorin.^94,95 The NSABP C-07 (Table 3) trial used a similar trial design but employed bolus fluorouracil. More than 2400 patients with stage II and III colon cancer were randomly assigned to bolus FULV or bolus fluorouracil, leucovorin, and oxaliplatin (FLOX). The addition of oxaliplatin significantly improved outcomes, with 4-year DFS of 67% versus 71.8% for FULV and FLOX, respectively, and a HR of death of 0.80 with FLOX.^59,96 The multicenter N016968 trial (Table 3) randomly assigned 1886 patients with stage III colon cancer to adjuvant capecitabine plus oxaliplatin (XELOX) or bolus fluorouracil plus leucovorin (FU/FA). The 3-year DFS was 70.9% versus 66.5% with XELOX and FU/FA, respectively, and 5-year OS was 77.6% versus 74.2%, respectively.^97,98

In the metastatic setting, additional agents have shown efficacy, including irinotecan,^99,100 bevacizumab,^101,102 cetuximab,^103,104 and regorafenib.¹⁰⁵ This observation led to testing of these agents in earlier stage disease. The CALGB 89803 trial compared fluorouracil, leucovorin, and irinotecan to fluorouracil with leucovorin alone. No benefit in 5-year DFS or OS was seen.¹⁰⁶ Similarly, infusional fluorouracil, leucovorin, and irinotecan (FOLFIRI) was not found to improve 5-year DFS as compared to fluorouracil with leucovorin alone in the PETACC-3 trial.¹⁰⁷ The NSABP C-08 trial considered the addition of bevacizumab to FOLFOX. When compared to FOLFOX alone, the combination of bevacizumab to FOLFOX had similar 3-year DFS (77.9% versus 75.1%) and 5-year OS (82.5% versus 80.7%).¹⁰⁸ This finding was confirmed in the Avant trial.¹⁰⁹ The addition of cetuximab to FOLFOX was equally disappointing, as shown in the N0147 trial110 and PETACC-8 trial.¹¹¹ Data on regorafenib in the adjuvant setting for stage III colon cancer is lacking; however, 2 ongoing clinical trials, NCT02425683 and NCT02664077, are each studying the use of regorafenib following completion of FOLFOX for patients with stage III disease.

Thus, after multiple trials comparing various regimens and despite attempts to improve outcomes by the addition of a third agent, the standard of care per National Comprehensive Cancer Network (NCCN) guidelines for management of stage III colon cancer remains 12 cycles of FOLFOX chemotherapy. Therapy should be initiated within 8 weeks of surgery. Data are emerging to support a short duration of therapy for patients with low-risk stage III tumors, as shown in an abstract presented at the 2017 American Society of Clinical Oncology annual meeting. The IDEA trial was a pooled analysis of 6 randomized clinical trials across multiple countries, all of which evaluated 3 versus 6 months of FOLFOX or capecitabine and oxaliplatin in the treatment of stage III colon cancer. The analysis was designed to test non-inferiority of 3 months of therapy as compared to 6 months. The analysis included 6088 patients across 244 centers in 6 countries. The overall analysis failed to establish noninferiority. The 3-year DFS rate was 74.6% for 3 months and 75.5% for 6 months, with a DFS HR of 1.07 and a confidence interval that did not meet the prespecified endpoint. Subgroup analysis suggested noninferiority for lower stage disease (T1–3 or N1) but not for higher stage disease (T4 or N2). Given the high rates of neuropathy with 6 months of oxaliplatin, these results suggest that 3 months of adjuvant therapy can be considered for patients with T1–3 or N1 disease in an attempt to limit toxicity.¹¹²

CASE PRESENTATION 2

A 57-year-old woman presents to the emergency department with fever and abdominal pain. CT of the abdomen and pelvis demonstrates a left-sided colonic mass with surrounding fat stranding and pelvic abscess. She is taken emergently for left hemicolectomy, cholecystectomy, and evacuation of pelvic abscess. Pathology reveals a 5-cm adenocarcinoma with invasion through the visceral peritoneum; 0/22 lymph nodes are involved. She is given a diagnosis of stage IIC and referred to medical oncology for further management. Due to her young age and presence of high-risk features, she is recommended adjuvant therapy with FOLFOX for 6 months.

ADJUVANT CHEMOTHERAPY IN STAGE II COLON CANCER

Because of excellent outcomes with surgical resection alone for stage II cancers, the use of adjuvant chemotherapy for patients with stage II disease is controversial. Limited prospective data is available to guide adjuvant treatment decisions for stage II patients. The QUASAR trial, which compared observation to adjuvant fluorouracil and leucovorin in patients with early-stage colon cancer, included 2963 patients with stage II disease and found a relative risk (RR) of death or recurrence of 0.82 and 0.78, respectively. Importantly, the absolute benefit of therapy was less than 5%.¹¹³ The IMPACT-B2 trial (Table 3) combined data from 5 separate trials and analyzed 1016 patients with stage II colon cancer who received fluorouracil with leucovorin or observation. Event-free survival was 0.86 versus 0.83 and 5-year OS was 82% versus 80%, suggesting no benefit.¹¹⁴ The benefit of addition of oxaliplatin to fluorouracil in stage II disease appears to be less than the benefit of adding this agent in the treatment of stage III CRC. As noted above, the MOSAIC trial randomly assigned patients with stage II and III colon cancer to receive adjuvant fluorouracil and leucovorin with or without oxaliplatin for 12 cycles. After a median follow-up of 9.5 years, 10-year OS rates for patients with stage II disease were 78.4% versus 79.5%. For patients with high-risk stage II disease (defined as T4, bowel perforation, or fewer than 10 lymph nodes examined), 10-year OS was 71.7% and 75.4% respectively, but these differences were not statistically significant.⁹⁴

Because of conflicting data as to the benefit of adding oxaliplatin in stage II disease, oxaliplatin is not recommended for standard-risk stage II patients. The use of oxaliplatin in high-risk stage II tumors should be weighed carefully given the toxicity risk. Oxaliplatin is recognized to cause sensory neuropathy in many patients, which can become painful and debilitating.¹¹⁵ Two types of neuropathy are associated with oxaliplatin: acute and chronic. Acute neuropathy manifests most often as cold-induced paresthesias in the fingers and toes and is quite common, affecting up to 90% of patients. These symptoms are self-limited and resolve usually within 1 week of each treatment.¹¹⁶ Some patients, with reports ranging from 10% to 79%, develop chronic neuropathy that persists for 1 year or more and causes significant decrements in quality of life.¹¹⁷ Patients older than age 70 may be at greater risk for oxaliplatin-induced neuropathy, which would increase risk of falls in this population.¹¹⁸ In addition to neuropathy, oxaliplatin is associated with hypersensitivity reactions that can be severe and even fatal.¹¹⁹ In a single institution series, the incidence of severe reactions was 2%.¹²⁰ Desensitization following hypersensitivity reactions is possible but requires a time-intensive protocol.¹²¹

Based on the inconclusive efficacy findings and due to concerns over toxicity, each decision must be individualized to fit patient characteristics and preferences. In general, for patients with stage II disease without high-risk features, an individualized discussion should be held as to the risks and benefits of single-agent fluorouracil, and this treatment should be offered in cases where the patient or provider would like to be aggressive. Patients with stage II cancer who have 1 or more high-risk features are often recommended adjuvant chemotherapy. Whether treatment with fluorouracil plus leucovorin or FOLFOX is preferred remains uncertain, and thus the risks and the potential gains of oxaliplatin must be discussed with the individual patient. MMR status can also influence the treatment recommendation for patients with stage II disease. In general, patients with standard-risk stage II tumors that are pMMR are offered MMR with leucovorin or oral capecitabine for 12 cycles. FOLFOX is considered for patients with MSI-high disease and those with multiple high-risk features.

MONITORING AFTER THERAPY

After completion of adjuvant chemotherapy, patients enter a period of survivorship. Patients are seen in clinic for symptom and laboratory monitoring of the complete blood count, liver function tests, and carcinoembryonic antigen (CEA). NCCN guidelines support history and physical examination with CEA testing every 3 to 6 months for the first 2 years, then every 6 months for the next 3 years, after which many patients continue to be seen annually. CT imaging of the chest, abdomen, and pelvis for monitoring of disease recurrence is recommended every 6 to 12 months for a total of 5 years. New elevations in CEA or liver function tests should prompt early imaging. Colonoscopy should be performed 1 year after completion of therapy; however, if no preoperative colonoscopy was performed, this should be done 3 to 6 months after completion. Colonoscopy is then repeated in 3 years and then every 5 years unless advanced adenomas are present.¹²²

SUMMARY

The addition of chemotherapy to surgical management of colon cancer has lowered the rate of disease recurrence and improved long-term survival. Adjuvant FOLFOX for 12 cycles is the standard of care for patients with stage III colon cancer and for patients with stage II disease with certain high-risk features. Use of adjuvant chemotherapy in stage II disease without high-risk features is controversial, and treatment decisions should be individualized. Biologic markers such as MSI and CDX2 status as well as patient-related factors including age, overall health, and personal preferences can inform treatment decisions. If chemotherapy is recommended in this setting, it would be with single-agent fluorouracil in an infusional or oral formulation, unless the tumor has the MSI-high feature. Following completion of adjuvant therapy, patients should be followed with clinical evaluation, laboratory testing, and imaging for a total of 5 years as per recommended guidelines.

INTRODUCTION

Colorectal cancer (CRC) is one of the most prevalent malignancies and is the fourth most common cancer in the United States, with an estimated 133,490 new cases diagnosed in 2016. Of these, approximately 95,520 are located in the colon and 39,970 are in the rectum.¹ CRC is the third leading cause of cancer death in women and the second leading cause of cancer death in men, with an estimated 49,190 total deaths in 2016.² The incidence appears to be increasing,³ especially in patients younger than 55 years of age;⁴ the reason for this increase remains uncertain.

A number of risk factors for the development of CRC have been identified. Numerous hered-itary CRC syndromes have been described, including familial adenomatous polyposis,⁵ hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome,⁶ and MUTYH-associated polyposis.^7,8 A family history of CRC doubles the risk of developing CRC,⁹ and current guidelines support lowering the age of screening in individuals with a family history of CRC to 10 years younger than the age of diagnosis of the family member or 40 years of age, whichever is lower.¹⁰ Patients with a personal history of adenomatous polyps are at increased risk for developing CRC, as are patients with a personal history of CRC, with a relative risk ranging from 3 to 6.¹¹ Ulcerative colitis and Crohn’s disease are associated with the development of CRC and also influence screening, though evidence suggests good control of these diseases may mitigate risk.¹² Finally, modifiable risk factors for the development of CRC include high red meat consumption,¹³ diets low in fiber,¹⁴ obesity,¹³ smoking, alcohol use,¹⁵ and physical inactivity¹⁶; lifestyle modification targeting these factors has been shown to decrease rates of CRC.¹⁷ The majority of colon cancers present with clinical symptoms, often with rectal bleeding, abdominal pain, change in bowel habits, or obstructive symptoms. More rarely, these tumors are detected during screening colonoscopy, in which case they tend to be at an early stage.

SURGICAL MANAGEMENT

A critical goal in the resection of early-stage colon cancer is attaining R0 resection. Patients who achieve R0 resection as compared to R1 (microscopic residual tumor) and R2 (macroscopic residual tumor)¹⁸ have significantly improved long-term overall survival.¹⁹ Traditionally, open resection of the involved colonic segment was employed, with end-end anastomosis of the uninvolved free margins. Laparoscopic resection for early-stage disease has been utilized in attempts to decrease morbidity of open procedures, with similar outcomes and node sampling.²⁰ Laparoscopic resection appears to provide similar outcomes even in locally advanced disease.²¹ Right-sided lesions are treated with right colectomy and primary ileocolic anastomosis.²² For patients presenting with obstructing masses, the Hartmann procedure is the most commonly performed operation. This involves creation of an ostomy with subtotal colectomy and subsequent ostomy reversal in a 2- or 3-stage protocol.²³ Patients with locally advanced disease and invasion into surrounding structures require multivisceral resection, which involves resection en bloc with secondarily involved organs.²⁴ Intestinal perforation presents a unique challenge and is associated with surgical complications, infection, and lower overall survival (OS) and 5-year disease-free survival (DFS). Complete mesocolic excision is a newer technique that has been performed with reports of better oncologic outcome at some centers; however, this approach is not currently considered standard of care.²⁵

STAGING

According to a report by the National Cancer Institute, the estimated 5-year relative survival rates for localized colon cancer (lymph node negative), regional (lymph node positive) disease, and distant (metastatic) disease are 89.9%, 71.3%, and 13.9%, respectively.¹ However, efforts have been made to further classify patients into distinct categories to allow fine-tuning of prognostication. In the current system, staging of colon cancer utilizes the American Joint Committee on Cancer tumor/node/metastasis (TNM) system.²⁰ Clinical and pathologic features include depth of invasion, local invasion of other organs, nodal involvement, and presence of distant metastasis (Table 1). Studies completed prior to the adoption of the TNM system used the Dukes criteria, which divided colon cancer into A, B, and C, corresponding to TNM stage I, stage IIA–IIC, and stage IIIA-IIIC. This classification is rarely used in more contemporary studies.

Adjuvant chemotherapy seeks to eliminate micrometastatic disease present following curative surgical resection. When stage 0 cancer is discovered incidentally during colonoscopy, endoscopic resection alone is the management of choice, as presence of micrometastatic disease is exceedingly unlikely.²⁶ Stage I–III CRCs are treated with surgical resection withcurative intent. The 5-year survival rate for stage I and early-stage II CRC is estimated at 97% with surgery alone.^27,28 The survival rate drops to about 60% for high-risk stage II tumors (T4aN0), and down to 50% or less for stage II-T4N0 or stage III cancers. Adjuvant chemotherapy is generally recommended to further decrease the rates of distant recurrence in certain cases of stage II and in all stage III tumors.

DETERMINATION OF BENEFIT FROM CHEMOTHERAPY: PROGNOSTIC MARKERS

Prior to administration of adjuvant chemotherapy, a clinical evaluation by the medical oncologist to determine appropriateness and safety of treatment is paramount. Poor performance status and comorbid conditions may indicate risk for excessive toxicity and minimal benefit from chemotherapy. CRC commonly presents in older individuals, with the median age at diagnosis of 69 years for men and 73 years for women.²⁹ In this patient population, comorbidities such as cardiovascular disease, diabetes, and renal dysfunction are more prevalent.³⁰ Decisions regarding adjuvant chemotherapy in this patient population have to take into consideration the fact that older patients may experience higher rates of toxicity with chemotherapy, including gastrointestinal toxicities and marrow suppression.³¹ Though some reports indicate patients older than 70 years derive similar benefit from adjuvant chemotherapy,^32,33 a large pooled analysis of the ACCENT database, which included 7 adjuvant therapy trials and 14,528 patients, suggested limited benefit from the addition of oxaliplatin to fluorouracil in elderly patients.³² Other factors that weigh on the decision include stage, pathology, and presence of high-risk features. A common concern in the postoperative setting is delaying initiation of chemotherapy to allow adequate wound healing; however, evidence suggests that delays longer than 8 weeks leads to worse overall survival, with hazard ratios (HR) ranging from 1.4 to 1.7.^34,35 Thus, the start of adjuvant therapy should ideally be within this time frame.

HIGH-RISK FEATURES

Multiple factors have been found to predict worse outcome and are classified as high-risk features (Table 2). Histologically, high-grade or poorly differentiated tumors are associated with higher recurrence rate and worse outcome.³⁶ Certain histological subtypes, including mucinous and signet-ring, both appear to have more aggressive biology.³⁷ Presence of microscopic invasion into surrounding blood vessels (vascular invasion) and nerves (perineural invasion) is associated with lower survival.³⁸ Penetration of the cancer through the visceral peritoneum (T4a) or into surrounding structures (T4b) is associated with lower survival.³⁶ During surgical resection, multiple lymph nodes are removed along with the primary tumor to evaluate for metastasis to the regional nodes. Multiple analyses have demonstrated that removal and pathologic assessment of fewer than 12 lymph nodes is associated with high risk of missing a positive node, and is thus equated with high risk.^39–41 In addition, extension of tumor beyond the capsules of any single lymph node, termed extracapsular extension, is associated with an increased risk of all-cause mortality.⁴² Tumor deposits, or focal aggregates of adenocarcinoma in the pericolic fat that are not contiguous with the primary tumor and are not associated with lymph nodes, are currently classified as lymph nodes as N1c in the current TNM staging system. Presence of these deposits has been found to predict poor outcome stage for stage.⁴³ Obstruction and/or perforation secondary to the tumor are also considered high-risk features that predict poor outcome.

SIDEDNESS

As reported at the 2016 American Society of Clinical Oncology annual meeting, tumor location predicts outcome in the metastatic setting. A report by Venook and colleagues based on a post-hoc analysis found that in the metastatic setting, location of the tumor primary in the left side is associated with longer OS (33.3 months) when compared to the right side of the colon (19.4 months).⁴⁴ A retrospective analysis of multiple databases presented by Schrag and colleagues similarly reported inferior outcomes in patients with stage III and IV disease who had right-sided primary tumors.⁴⁵ However, the prognostic implications for stage II disease remain uncertain.

BIOMARKERS

Given the controversy regarding adjuvant therapy of patients with stage II colon cancer, multiple biomarkers have been evaluated as possible predictive markers that can assist in this decision. The mismatch repair (MMR) system is a complex cellular enzymatic mechanism that identifies and corrects DNA errors during cell division and prevents mutagenesis.⁴⁶ The familial cancer syndrome HNPCC is linked to alteration in a variety of MMR genes, leading to deficient mismatch repair (dMMR), also termed microsatellite instability-high (MSI-high).^47,48 Epigenetic modification can also lead to silencing of the same implicated genes and accounts for 15% to 20% of sporadic colorectal cancer.⁴⁹ These epigenetic modifications lead to hypermethylation of the promotor region of MLH1 in 70% of cases.⁵⁰ The 4 MMR genes most commonly tested are MLH-1, MSH2, MSH6, and PMS2. Testing can be performed by immunohistochemistry or polymerase chain reaction.⁵¹ Across tumor histology and stage, MSI status is prognostic. Patients with MSI-high tumors have been shown to have improved prognosis and longer OS both in stage II and III disease^52–54 and in the metastatic setting.⁵⁵ However, despite this survival benefit, there is conflicting data as to whether patients with stage II, MSI-high colon cancer may benefit less from adjuvant chemotherapy. One early retrospective study compared outcomes of 70 patients with stage II and III disease and dMMR to those of 387 patients with stage II and III disease and proficient mismatch repair (pMMR). Adjuvant fluorouracil with leucovorin improved DFS for patients with pMMR (HR 0.67) but not for those with dMMR (HR 1.10). In addition, for patients with stage II disease and dMMR, the HR for OS was inferior at 2.95.⁵⁶ Data collected from randomized clinical trials using fluorouracil-based adjuvant chemotherapy were analyzed in an attempt to predict benefit based on MSI status. Benefit was only seen in pMMR patients, with a HR of 0.72; this was not seen in the dMMR patients.⁵⁷ Subsequent studies have had different findings and did not demonstrate a detrimental effect of fluorouracil in dMMR.^58,59 For stage III patients, MSI status does not appear to affect benefit from chemotherapy, as analysis of data from the NSABP C-07 trial (Table 3) demonstrated benefit of FOLFOX (leucovorin, fluorouracil, oxaliplatin) in patients with dMMR status and stage III disease.⁵⁹

Another genetic abnormality identified in colon cancers is chromosome 18q loss of heterozygosity (LOH). The presence of 18q LOH appears to be inversely associated with MSI-high status. Some reports have linked presence of 18q with worse outcome,⁶⁰ but others question this, arguing the finding may simply be related to MSI status.^61,62 This biomarker has not been established as a clear prognostic marker that can aid clinical decisions.

Most recently, expression of caudal-type homeobox transcription factor 2 (CDX2) has been reported as a novel prognostic and predictive tool. A 2015 report linked lack of expression of CDX2 to worse outcome; in this study, 5-year DFS was 41% in patients with CDX2-negative tumors versus 74% in the CDX2-positive tumors, with a HR of disease recurrence of 2.73 for CDX2-negative tumors.⁶³ Similar numbers were observed in patients with stage II disease, with 5-year OS of 40% in patients with CDX2-negative tumors versus 70% in those with CDX2-positive tumors. Treatment of CDX2-negative patients with adjuvant chemotherapy improved outcomes: 5-year DFS in the stage II subgroup was 91% with chemotherapy versus 56% without, and in the stage III subgroup, 74% with chemotherapy versus 37% without. The authors concluded that patients with stage II and III colon cancer that is CDX2-negative may benefit from adjuvant chemotherapy. Importantly, CDX2-negativity is a rare event, occurring in only 6.9% of evaluable tumors.

RISK ASSESSMENT TOOLS

Several risk assessment tools have been developed in an attempt to aid clinical decision making regarding adjuvant chemotherapy for patients with stage II colon cancer. The Oncotype DX Colon Assay analyses a 12-gene signature in the pathologic sample and was developed with the goal to improve prognostication and aid in treatment decision making. The test utilizes reverse transcription-PCR on RNA extracted from the tumor.⁶⁴ After evaluating 12 genes, a recurrence score is generated that predicts the risk of disease recurrence. This score was validated using data from 3 large clinical trials.^65–67 Unlike the Oncotype Dx score used in breast cancer, the test in colon cancer has not been found to predict the benefit from chemotherapy and has not been incorporated widely into clinical practice.

Adjuvant! Online (available at www.adjuvantonline.com) is a web-based tool that combines clinical and histological features to estimate outcome. Calculations are based on US SEER tumor registry-reported outcomes.⁶⁸ A second web-based tool, Numeracy (available at www.mayoclinic.com/calcs), was developed by the Mayo Clinic using pooled data from 7 randomized clinical trials including 3341 patients.⁶⁸ Both tools seek to predict absolute benefit for patients treated with fluorouracil, though data suggests Adjuvant! Online may be more reliable in its predictive ability.⁶⁹ Adjuvant! Online has also been validated in an Asian population70 and patients older than 70 years.⁷¹

MUTATIONAL ANALYSIS

Multiple mutations in proto-oncogenes have been found in colon cancer cells. One such proto-oncogene is BRAF, which encodes a serine-threonine kinase in the rapidly accelerated fibrosarcoma (RAF). Mutations in BRAF have been found in 5% to 10% of colon cancers and are associated with right-sided tumors.⁷² As a prognostic marker, some studies have associated BRAF mutations with worse prognosis, including shorter time to relapse and shorter OS.^73,74 Two other proto-oncogenes are Kristen rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma rat sarcoma viral oncogene homolog (NRAS), both of which encode proteins downstream of epidermal growth factor receptor (EGFR). KRAS and NRAS mutations have been shown to be predictive in the metastatic setting where they predict resistance to the EGFR inhibitors cetuximab and panitumumab.^75,76 The effect of KRAS and NRAS mutations on outcome in stage II and III colon cancer is uncertain. Some studies suggest worse outcome in KRAS-mutated cancers,⁷⁷ while others failed to demonstrate this finding.⁷³

CASE PRESENTATION 1

A 53-year-old man with no past medical history presents to the emergency department with early satiety and generalized abdominal pain. Laboratory evaluation shows a microcytic anemia with normal white blood cell count, platelet count, renal function, and liver function tests. Computed tomography (CT) scan of the abdomen and pelvis show a 4-cm mass in the transverse colon without obstruction and without abnormality in the liver. CT scan of the chest does not demonstrate pathologic lymphadenopathy or other findings. He undergoes robotic laparoscopic transverse colon resection and appendectomy. Pathology confirms a 3.5-cm focus of adenocarcinoma of the colon with invasion through the muscularis propria and 5 of 27 regional lymph nodes positive for adenocarcinoma and uninvolved proximal, distal, and radial margins. He is given a stage of IIIB pT3 pN2a M0 and referred to medical oncology for further management, where 6 months of adjuvant FOLFOX chemotherapy is recommended.

ADJUVANT CHEMOTHERAPY IN STAGE III COLON CANCER

Postoperative adjuvant chemotherapy is the standard of care for patients with stage III disease. In the 1960s, infusional fluorouracil was first used to treat inoperable colon cancer.^78,79 After encouraging results, the agent was used both intraluminally and intravenously as an adjuvant therapy for patients undergoing resection with curative intent; however, only modest benefits were described.^80,81 The National Surgical Adjuvant Breast and Bowel Project (NSABP) C-01 trial (Table 3) was the first study to demonstrate a benefit from adjuvant chemotherapy in colon cancer. This study randomly assigned patients with stage II and III colon cancer to surgery alone, postoperative chemotherapy with fluorouracil, semustine, and vincristine (MOF), or postoperative bacillus Calmette-Guérin (BCG). DFS and OS were significantly improved with MOF chemotherapy.⁸² In 1990, a landmark study reported on outcomes after treatment of 1296 patients with stage III colon cancer with adjuvant fluorouracil and levamisole for 12 months. The combination was associated with a 41% reduction in risk of cancer recurrence and a 33% reduction in risk of death.⁸³ The NSABP C-03 trial (Table 3) compared MOF to the combination of fluorouracil and leucovorin and demonstrated improved 3-year DFS (69% versus 73%) and 3-year OS (77% versus 84%) in patients with stage III disease.⁸⁴ Building on these outcomes, the QUASAR study (Table 3) compared fluorouracil in combination with one of levamisole, low-dose leucovorin, or high-dose leucovorin. The study enrolled 4927 patients and found worse outcomes with fluorouracil plus levamisole and no difference in low-doseversus high-dose leucovorin.⁸⁵ Levamisole fell out of use after associations with development of multifocal leukoencephalopathy,⁸⁶ and was later shown to have inferior outcomes versus leucovorin when combined with fluorouracil.^87,88 Intravenous fluorouracil has shown similar benefit when administered by bolus or infusion,⁸⁹ although continuous infusion has been associated with lower incidence of severe toxicity.⁹⁰ The efficacy of the oral fluoropyrimidine capecitabine has been shown to be equivalent to that of fluorouracil.⁹¹

Fluorouracil-based treatment remained the standard of care until the introduction of oxaliplatin in the mid-1990s. After encouraging results in the metastatic setting,^92,93 the agent was moved to the adjuvant setting. The MOSAIC trial (Table 3) randomly assigned patients with stage II and III colon cancer to fluorouracil with leucovorin (FULV) versus FOLFOX given once every 2 weeks for 12 cycles. Analysis with respect to stage III patients showed a clear survival benefit, with a 10-year OS of 67.1% with FOLFOX chemotherapy versus 59% with fluorouracil and leucovorin.^94,95 The NSABP C-07 (Table 3) trial used a similar trial design but employed bolus fluorouracil. More than 2400 patients with stage II and III colon cancer were randomly assigned to bolus FULV or bolus fluorouracil, leucovorin, and oxaliplatin (FLOX). The addition of oxaliplatin significantly improved outcomes, with 4-year DFS of 67% versus 71.8% for FULV and FLOX, respectively, and a HR of death of 0.80 with FLOX.^59,96 The multicenter N016968 trial (Table 3) randomly assigned 1886 patients with stage III colon cancer to adjuvant capecitabine plus oxaliplatin (XELOX) or bolus fluorouracil plus leucovorin (FU/FA). The 3-year DFS was 70.9% versus 66.5% with XELOX and FU/FA, respectively, and 5-year OS was 77.6% versus 74.2%, respectively.^97,98

In the metastatic setting, additional agents have shown efficacy, including irinotecan,^99,100 bevacizumab,^101,102 cetuximab,^103,104 and regorafenib.¹⁰⁵ This observation led to testing of these agents in earlier stage disease. The CALGB 89803 trial compared fluorouracil, leucovorin, and irinotecan to fluorouracil with leucovorin alone. No benefit in 5-year DFS or OS was seen.¹⁰⁶ Similarly, infusional fluorouracil, leucovorin, and irinotecan (FOLFIRI) was not found to improve 5-year DFS as compared to fluorouracil with leucovorin alone in the PETACC-3 trial.¹⁰⁷ The NSABP C-08 trial considered the addition of bevacizumab to FOLFOX. When compared to FOLFOX alone, the combination of bevacizumab to FOLFOX had similar 3-year DFS (77.9% versus 75.1%) and 5-year OS (82.5% versus 80.7%).¹⁰⁸ This finding was confirmed in the Avant trial.¹⁰⁹ The addition of cetuximab to FOLFOX was equally disappointing, as shown in the N0147 trial110 and PETACC-8 trial.¹¹¹ Data on regorafenib in the adjuvant setting for stage III colon cancer is lacking; however, 2 ongoing clinical trials, NCT02425683 and NCT02664077, are each studying the use of regorafenib following completion of FOLFOX for patients with stage III disease.

Thus, after multiple trials comparing various regimens and despite attempts to improve outcomes by the addition of a third agent, the standard of care per National Comprehensive Cancer Network (NCCN) guidelines for management of stage III colon cancer remains 12 cycles of FOLFOX chemotherapy. Therapy should be initiated within 8 weeks of surgery. Data are emerging to support a short duration of therapy for patients with low-risk stage III tumors, as shown in an abstract presented at the 2017 American Society of Clinical Oncology annual meeting. The IDEA trial was a pooled analysis of 6 randomized clinical trials across multiple countries, all of which evaluated 3 versus 6 months of FOLFOX or capecitabine and oxaliplatin in the treatment of stage III colon cancer. The analysis was designed to test non-inferiority of 3 months of therapy as compared to 6 months. The analysis included 6088 patients across 244 centers in 6 countries. The overall analysis failed to establish noninferiority. The 3-year DFS rate was 74.6% for 3 months and 75.5% for 6 months, with a DFS HR of 1.07 and a confidence interval that did not meet the prespecified endpoint. Subgroup analysis suggested noninferiority for lower stage disease (T1–3 or N1) but not for higher stage disease (T4 or N2). Given the high rates of neuropathy with 6 months of oxaliplatin, these results suggest that 3 months of adjuvant therapy can be considered for patients with T1–3 or N1 disease in an attempt to limit toxicity.¹¹²

CASE PRESENTATION 2

A 57-year-old woman presents to the emergency department with fever and abdominal pain. CT of the abdomen and pelvis demonstrates a left-sided colonic mass with surrounding fat stranding and pelvic abscess. She is taken emergently for left hemicolectomy, cholecystectomy, and evacuation of pelvic abscess. Pathology reveals a 5-cm adenocarcinoma with invasion through the visceral peritoneum; 0/22 lymph nodes are involved. She is given a diagnosis of stage IIC and referred to medical oncology for further management. Due to her young age and presence of high-risk features, she is recommended adjuvant therapy with FOLFOX for 6 months.

ADJUVANT CHEMOTHERAPY IN STAGE II COLON CANCER

Because of excellent outcomes with surgical resection alone for stage II cancers, the use of adjuvant chemotherapy for patients with stage II disease is controversial. Limited prospective data is available to guide adjuvant treatment decisions for stage II patients. The QUASAR trial, which compared observation to adjuvant fluorouracil and leucovorin in patients with early-stage colon cancer, included 2963 patients with stage II disease and found a relative risk (RR) of death or recurrence of 0.82 and 0.78, respectively. Importantly, the absolute benefit of therapy was less than 5%.¹¹³ The IMPACT-B2 trial (Table 3) combined data from 5 separate trials and analyzed 1016 patients with stage II colon cancer who received fluorouracil with leucovorin or observation. Event-free survival was 0.86 versus 0.83 and 5-year OS was 82% versus 80%, suggesting no benefit.¹¹⁴ The benefit of addition of oxaliplatin to fluorouracil in stage II disease appears to be less than the benefit of adding this agent in the treatment of stage III CRC. As noted above, the MOSAIC trial randomly assigned patients with stage II and III colon cancer to receive adjuvant fluorouracil and leucovorin with or without oxaliplatin for 12 cycles. After a median follow-up of 9.5 years, 10-year OS rates for patients with stage II disease were 78.4% versus 79.5%. For patients with high-risk stage II disease (defined as T4, bowel perforation, or fewer than 10 lymph nodes examined), 10-year OS was 71.7% and 75.4% respectively, but these differences were not statistically significant.⁹⁴

Because of conflicting data as to the benefit of adding oxaliplatin in stage II disease, oxaliplatin is not recommended for standard-risk stage II patients. The use of oxaliplatin in high-risk stage II tumors should be weighed carefully given the toxicity risk. Oxaliplatin is recognized to cause sensory neuropathy in many patients, which can become painful and debilitating.¹¹⁵ Two types of neuropathy are associated with oxaliplatin: acute and chronic. Acute neuropathy manifests most often as cold-induced paresthesias in the fingers and toes and is quite common, affecting up to 90% of patients. These symptoms are self-limited and resolve usually within 1 week of each treatment.¹¹⁶ Some patients, with reports ranging from 10% to 79%, develop chronic neuropathy that persists for 1 year or more and causes significant decrements in quality of life.¹¹⁷ Patients older than age 70 may be at greater risk for oxaliplatin-induced neuropathy, which would increase risk of falls in this population.¹¹⁸ In addition to neuropathy, oxaliplatin is associated with hypersensitivity reactions that can be severe and even fatal.¹¹⁹ In a single institution series, the incidence of severe reactions was 2%.¹²⁰ Desensitization following hypersensitivity reactions is possible but requires a time-intensive protocol.¹²¹

Based on the inconclusive efficacy findings and due to concerns over toxicity, each decision must be individualized to fit patient characteristics and preferences. In general, for patients with stage II disease without high-risk features, an individualized discussion should be held as to the risks and benefits of single-agent fluorouracil, and this treatment should be offered in cases where the patient or provider would like to be aggressive. Patients with stage II cancer who have 1 or more high-risk features are often recommended adjuvant chemotherapy. Whether treatment with fluorouracil plus leucovorin or FOLFOX is preferred remains uncertain, and thus the risks and the potential gains of oxaliplatin must be discussed with the individual patient. MMR status can also influence the treatment recommendation for patients with stage II disease. In general, patients with standard-risk stage II tumors that are pMMR are offered MMR with leucovorin or oral capecitabine for 12 cycles. FOLFOX is considered for patients with MSI-high disease and those with multiple high-risk features.

MONITORING AFTER THERAPY

After completion of adjuvant chemotherapy, patients enter a period of survivorship. Patients are seen in clinic for symptom and laboratory monitoring of the complete blood count, liver function tests, and carcinoembryonic antigen (CEA). NCCN guidelines support history and physical examination with CEA testing every 3 to 6 months for the first 2 years, then every 6 months for the next 3 years, after which many patients continue to be seen annually. CT imaging of the chest, abdomen, and pelvis for monitoring of disease recurrence is recommended every 6 to 12 months for a total of 5 years. New elevations in CEA or liver function tests should prompt early imaging. Colonoscopy should be performed 1 year after completion of therapy; however, if no preoperative colonoscopy was performed, this should be done 3 to 6 months after completion. Colonoscopy is then repeated in 3 years and then every 5 years unless advanced adenomas are present.¹²²

SUMMARY

The addition of chemotherapy to surgical management of colon cancer has lowered the rate of disease recurrence and improved long-term survival. Adjuvant FOLFOX for 12 cycles is the standard of care for patients with stage III colon cancer and for patients with stage II disease with certain high-risk features. Use of adjuvant chemotherapy in stage II disease without high-risk features is controversial, and treatment decisions should be individualized. Biologic markers such as MSI and CDX2 status as well as patient-related factors including age, overall health, and personal preferences can inform treatment decisions. If chemotherapy is recommended in this setting, it would be with single-agent fluorouracil in an infusional or oral formulation, unless the tumor has the MSI-high feature. Following completion of adjuvant therapy, patients should be followed with clinical evaluation, laboratory testing, and imaging for a total of 5 years as per recommended guidelines.

Almost half of Crohn disease (CD) patients experience a dermatologic manifestation of the disease. A rare entity, metastatic CD (MCD) presents a diagnostic challenge without a high index of suspicion. Its etiology is not well defined; however, it appears to be an autoimmune response to gut antigens. Herein, we review the etiology/epidemiology, diagnostic criteria, and treatment for this uncommon condition.

Epidemiology and Clinical Characteristics of MCD

Metastatic CD was first described by Parks et al1 in 1965 and refers to a diverse collection of macroscopic dermatologic manifestations in tissue not contiguous with the gastrointestinal (GI) tract. To be classified as MCD, the tissue must demonstrate characteristic histopathologic findings, which invariably include noncaseating granulomas.

Crohn disease may affect any part of the GI tract from the mouth to anus, with a multitude of associated cutaneous manifestations having been described. The terminal ileum is the most commonly affected portion of the GI tract in CD, but the large intestine also may be involved in 55% to 80% of cases.² The incidence of non-MCD-associated anal lesions seems to correlate with intestinal involvement in that as few as 25% of patients with ileal-localized CD have anal lesions compared to nearly 80% of patients with large intestinal involvement.³

It has been estimated that 18% to 44% of patients with CD have some form of cutaneous manifestation,⁴ with MCD being a rare subcategory. As few as 100 cases have been described from 1965 to the present.⁵ The presence of MCD does not correlate well with severity of intestinal CD, and although a majority of MCD cases present after at least 6 months of GI symptoms,⁶ there are instances in which MCD presents without prior or existing evidence of intestinal CD.⁷

With regard to MCD, the term metastatic is sometimes supplanted in the literature by cutaneous to avoid any implication of cancer; however, due to a myriad of dermatologic manifestations, both terms can cause confusion. The categorization of the various types of cutaneous findings in CD is well summarized in a review by Palamaras et al8 with the following classifications: (1) granulomatous by direct extension (oral or perianal), (2) MCD lesions (genital and nongenital), (3) immune-related lesions, and (4) lesions from nutritional deficiencies. Of the cutaneous manifestations relating to CD, MCD is the least common cutaneous categorical manifestation and is further divided into subcategories of genital and nongenital lesions.⁸

The nongenital distribution of MCD is the more common variety in adults and particularly seems to affect the legs and plantar surfaces (38%), the trunk and abdomen (24%), and the face (15%).^5,9 These nongenital MCD manifestations are most commonly described as nodules, ulcerations, or erythematous to purple plaques, and less commonly described as abscesses, pustules, or papules.

The sequence of cutaneous symptoms of MCD relative to intestinal disease depends to some degree on patient age. In adults diagnosed with MCD, it has been noted that a GI flare is expected 2 months to 4 years after diagnosis; however, in children the subsequent GI flare has been noted to vary more widely from 9 months to 14 years following presentation of MCD.⁸ Furthermore, roughly 50% of children diagnosed with MCD present concomitantly with their first symptoms of a GI flare, whereas 70% of adults with MCD had been previously diagnosed with intestinal CD.⁸ In one review of 80 reported cases of MCD, 20% (16/80) had no symptoms of intestinal disease at the time of MCD diagnosis, and the majority of the asymptomatic cases were in children; interestingly, the majority of these same children were diagnosed with CD months to years later.⁹

Both the location and characteristics of cutaneous findings in MCD correlate with age.⁹ Metastatic CD has been identified in all age groups; however, lymphedema is more common in children/young adults, while nodules, ulceration, and fistulating disease are more often seen in adults.¹⁰ Affected children and adolescents with MCD range from 5 to 17 years of age, with a mean age at disease onset of 11.1 years and equal incidence in males and females.⁸ Adults with MCD range from 18 to 78 years of age, with a mean age at presentation of 38.4 years.^8,11

Concerning anatomic location of disease, adults with MCD most commonly have nodules with or without plaques on the arms and legs and less commonly in the genital area.⁸ In contrast, children with MCD are more prone to genital lesions, with up to 85% of cases including some degree of genital erythematous or nonerythematous swelling with or without induration.⁸ Genitourinary complications of CD as a broad category, however, are estimated to occur in only 5% to 20% of intestinal CD cases in both children and adults.¹²

There have been conflicting reports regarding gender predilection in MCD. Based on a review by Samitz et al¹³ of 200 cases of CD over an 18-year period, 22% of patients with CD were found to have cutaneous manifestations--presumably not MCD but rather perianal, perineal, vulvar fistulae, fissures, or abscesses--with a male to female preponderance of almost 2 to 1. A more recent review of the literature by Palamaras et al⁸ in 2008 reported that contiguous non-MCD affects adult females and children more often than adult males, with 63% adult cases being female. This review seems to be more congruent with other reports in the literature implicating that females are twice as commonly affected by MCD than males.^9,14

Pathophysiology

The etiology of MCD has not been well defined. One proposed mechanism of the distal tissue involvement of MCD is through passage of antigens to the skin with subsequent granulomatous response at the level of the dermis.¹⁰ Another proposed mechanism suggests antibody sensitization to gut antigens, possibly bacterial antigens, that then coincidentally cross-react with analogous skin antigens.^8,14 Burgdorf¹¹ supported this notion in a 1981 report in which it was suggested that the granulomatous reaction was related to deposition of immune complexes in the skin. Slater et al¹⁵ and Tatnall et al¹⁶ offered a variation of Burgdorf's notion, suggesting that it was sensitized T cells to circulating antigens that were the initiators of granuloma formation in the periphery.

An examination of MCD tissue in 1990 by Shum and Guenther¹⁷ under electron microscopy and immunofluorescence provided evidence against prior studies that purported to have identified immune complexes as the causative agents of MCD. In this study, the authors found no evidence of immune complexes in the dermis of MCD lesions. In addition, an attempt to react serum antibodies of a patient with MCD, which were postulated to have IgG, IgM, and IgA antibodies to specific gut antigens, yielded no response when reacted with the tongue, ileum, and colon tissue from a rat. As a culminant finding, the authors also noted MCD dermis tissue with granulomas without vasculitis, suggesting a T-cell mediated type IV hypersensitivity response with a secondary vasculitis from T-cell origin lymphokines and T-cell mediated monocyte activation.¹⁷

Research implicating other immunologic entities involved in the pathophysiology of CD such as β-2 integrin,¹⁸ CD14⁺ monocytes,¹⁹ and the role of the DNA repair gene MLH1 (mutL homolog 1)²⁰ have been considered but without a clearly definitive role in the manifestations of MCD.

The utility of metronidazole in the treatment of MCD has been suggested as evidence that certain bacteria in the gut may either serve as the causative antigen or may induce its formation²¹; however, the causative antigen has yet to be identified, and whether it travels distally to the skin or merely resembles a similar antigen normally present in the dermis has not yet been determined. Some research has used in situ polymerase chain reaction techniques to attempt to detect similar microbial pathogens in both the vasculature of active bowel lesions and in the skin, but to date, bacterial RNA noted to be present in the gut vasculature adjacent to CD lesions has not been detected in skin lesions.²²

Diagnosis

Physical Findings

Overall, it is estimated that roughly 56% of all MCD cases affect the external genitalia.²³ The classic appearance of MCD includes well-demarcated ulcerations in the areas of intertriginous skin folds with or without diffuse edema and tenderness to palpation.²³ Although MCD has been historically noted as having a predilection for moist skin folds, there are numerous case reports of MCD all over the body, including the face,^7,24-29 retroauricular areas,³⁰ arms and legs,^16,17,31-34 lower abdomen,^3,5 under the breasts,¹ perineum,³⁵ external genitalia,^1,9,36-40 and even the lungs⁴¹ and bladder.⁴²

As a dermatologic disease, MCD has been referred to as yet another great imitator, both on the macroscopic and microscopic levels.⁸ As such, more common causes of genital edema should be considered first and investigated based on the patient's history, physical examination, skin biopsy, lymphangiogram, ultrasound, and cystogram.⁴³ Ultrasonography and color Doppler sonography have been shown to be helpful in patients with genital involvement. This modality can evaluate not only the presence of normal testes but also intratesticular and scrotal wall fluid, especially when the physical examination reveals swelling that makes testicle palpation more difficult.⁶ Clinically, the correct diagnosis of MCD often is made through suspicion of inflammatory bowel disease based on classic symptoms and/or physical findings including abdominal pain, weight loss, bloody stool, diarrhea, perianal skin tags, and anal fissures or fistulas. Any of these GI findings should prompt an intestinal biopsy to rule out any histologic evidence of CD.

Metastatic CD affecting the vulva often presents with vulvar pain and pruritus and may clinically mimic a more benign disease such as balanitis plasmacellularis, also referred to as Zoon vulvitis.²³ Similar to MCD on any given body surface, there is dramatic variation in the macroscopic presentation of vulvar MCD, with physical examination findings ranging from bilateral diffuse, edematous, deeply macerated, red, ulcerated lesions over the vulva with lymphadenopathy to findings of bilateral vulvar pain with yellow drainage from the labia majora.²³ There have been cases of vulvar MCD that include exquisite vulvar pain but without structural abnormalities including normal uterus, cervix, adnexa, rectovaginal septum, and rectum. In these more nebulous cases of vulvar MCD, the diagnosis often is discovered incidentally when nonspecific diagnostic imaging suggests underlying CD.²³

Beyond the case-by-case variations on physical examination, the great difficulty in diagnosis, particularly in children, occurs in the absence of any GI symptoms and therefore no logical consideration of underlying CD. Consequently, there have been cases of children presenting with irritation of the vulva who were eventually diagnosed with MCD only after erroneous treatment of contact dermatitis, candidiasis, and even consideration of sexual abuse.³⁷ Because it is so rare and obscure among practicing clinicians, the diagnosis of MCD often is considered only after irritation or swelling of the external genitalia has not responded to standard therapies. If and when the diagnosis of MCD is considered in children, it has been suggested to screen patients for anorectal stricture, as case studies have found the condition to be relatively common in this subpopulation.⁴⁴

In the less common case of adults with genitourinary symptoms that suggest possible MCD, the differential diagnosis for penile or vaginal ulcers should include contact and irritant dermatitis, chronic infectious lesions (eg, hidradenitis suppurativa, actinomycosis, tuberculosis),⁴⁵ sexually transmitted ulcerative diseases (eg, chancroid, lymphogranuloma venereum, herpes genitalia, granuloma inguinale),⁴⁶ drug reactions, and even extramammary Paget disease.⁴⁷

Histologic Findings

Because MCD has so much macroscopic variation and can present anywhere on the surface of the body, formal diagnosis relies on microscopy. As an added measure of difficulty in diagnosis, one random biopsy of a suspicious segment of tissue may not contain the expected histologic findings; therefore, clinical suspicion may warrant a second biopsy.¹⁰ There have been reported cases of an adult patient without history of CD presenting with a lesion that resembled a more common pathology, such as a genital wart, and the correct diagnosis of MCD with pseudocondylomatous morphology was made only after intestinal manifestations prompted the clinician to consider such an unusual diagnosis.⁴⁸

From a histopathologic perspective, MCD is characterized by discrete, noncaseating, sarcoidlike granulomas with abundant multinucleated giant cells (Langhans giant cells) in the superficial dermis (papillary), deep dermis (reticular), and adipose tissue (Figure).^8,17 In the presence of concomitant intestinal disease, the granulomas of both the intestinal and dermal tissues should share the same microscopic characteristics.⁸ In addition, copious neutrophils and granulomas surrounding the microvasculature have been described,³⁴ as well as general lymphocyte and plasma cell infiltrate.⁴⁵ Some histologic samples have included collagen degeneration termed necrobiosis in the middle dermal layer as another variable finding in MCD.^14,34

On microscopy, it has been reported that use of Verhoeff-van Gieson staining may be helpful to highlight the presence of neutrophil obstruction within the dermal vasculature, particularly the arterial lumen, as well as to aid in highlighting swelling of the endothelium with fragmentation of the internal elastic lamina.¹⁷ Although not part of the routine diagnosis, electron microscopy of MCD tissue samples have confirmed hypertrophy of the endothelial cells composing the capillaries with resulting extravasation of fibrin, red blood cells, lymphocytes, and epithelioid histiocytes.¹⁷ Observation of tissue under direct immunofluorescence has been less helpful, as it has shown only nonspecific fibrinogen deposition within the dermis and dermal vessels.¹⁷

In an article on treatment of MCD, Escher et al⁴³ reinforced that the macroscopic findings of MCD are diverse, and the microscopic findings characteristic of MCD also can be mimicked by other etiologies such as sarcoidosis, tuberculosis, fungal infections, lymphogranuloma venereum, leishmaniasis, and connective tissue disorders.⁴³ As such, the workup to rule out infectious, anatomic, and autoimmune etiologies should be diverse. Often, the workup for MCD will include special stains such as Ziehl-Neelsen stain to rule out Mycobacterium tuberculosis and acid-fast bacilli and Fite stain to consider atypical mycobacteria. Other tests such as tissue culture, chest radiograph, tuberculin skin test (Mantoux test), IFN-γ release assay, or polarized light microscopy may rule out infectious etiologies.^9,49 Serologic testing might include VDRL test, Treponema pallidum hemagglutination assay, hepatitis B, hepatitis C, and human immunodeficiency virus.⁵

Crohn disease is characterized histologically by sarcoidlike noncaseating granulomas, and as such, it is important to differentiate MCD from sarcoidosis prior to histologic analysis. Sarcoidosis also can be considered much less likely with a normal chest radiograph and in the absence of increased serum calcium and angiotensin-converting enzyme levels.⁷ The differentiation of sarcoidosis from MCD on the microscopic scale is subtle but is sometimes facilitated in the presence of an ulcerated epidermis or lymphocytic/eosinophilic infiltrate and edema within the dermis, all suggestive of MCD.¹⁴

Metastatic CD also should be differentiated from erythema nodosum and pyoderma gangrenosum, which are among the most common cutaneous findings associated with CD.¹⁴ Pyoderma gangrenosum can be distinguished histologically by identifying copious neutrophilic infiltrate with pseudoepitheliomatous hyperplasia.⁵⁰

Treatment

Because MCD is relatively rare, there are no known randomized trials suggesting a particular medical or surgical treatment. In a review of perineal MCD from 2007, the 40-year-old recommendation by Moutain³ opting for surgical debridement versus medical management still resonates, particularly for perineal disease, as an effective measure in all but the mildest of presentations.⁵¹ However, recent case reports also suggest that the tumor necrosis factor α (TNF-α) inhibitors such as infliximab and adalimumab should be considered prior to surgery even with severe perineal MCD.⁵¹ Moreover, even if medical management with TNF-α inhibitors or some combination of immunosuppressants and antibiotics does not eradicate the disease, it often helps reduce the size of the ulcers prior to surgery.⁵² With a limited understanding of MCD, one might think that removal of the affected bowel would eliminate cutaneous disease, but it has been shown that this strategy is not effective.^53,54

The composition and location of the particular lesion affects the trajectory of treatment. For example, MCD manifesting as local ulcers and plaques has been described as responding well to topical and intralesional steroids.^10,55,56 In the case of penile swelling and/or phimosis, circumcision has been helpful to improve the patient's ability to void as well as to attain and maintain erection.¹⁰ In the case of scrotal swelling secondary to MCD, early treatment (ie, within 4 to 6 months) with oral steroids and/or metronidazole is likely beneficial to prevent refractory edematous organization of the tissue.⁵⁷

As a general rule, an effective treatment will include a combination of an immunosuppressant, antibiotic therapy, and sometimes surgery. The most commonly used immunosuppressant agents include topical or intralesional steroids, infliximab,^43,58 cyclosporine A,^59,60 dapsone, minocycline, thalidomide, methotrexate, mycophenolate mofetil, sulfasalazine, azathioprine, tacrolimus, and 6-mercaptopurine.⁴ Steroids have been the conventional treatment of extraintestinal manifestations of CD⁶¹; however, perineal CD has been poorly controlled with systemic steroids.⁶² If steroids are found not to be effective, sometimes agents such as dapsone or thalidomide are considered. One case report noted stabilization of MCD penile ulcers with oral thalidomide 300 mg once daily, oral minocycline 100 mg once daily, and topical tacrolimus 0.3% with benzocaine twice daily with continuation of prednisolone and methotrexate as parts of previously unsuccessful regimen.⁵²

Metronidazole is perhaps the most commonly used antibiotic, having been a component of many successful regimens.^4,63 For example, a 27-year-old patient with MCD presenting as a nonhealing ulcerative lesion in the subcoronal area of the penis and scrotum was treated successfully with a 6-month course of mesalamine, prednisone, and metronidazole.⁴⁵ Another case report of vulvar MCD reported initial success with intravenous methylprednisolone, ciprofloxacin, and metronidazole.²³ The primary limitation of metronidazole is that subsequent tapering of the dose seems to result in recurrence of disease.⁶⁴ Consequently, patients must remain on the antibiotic for an indeterminate course, with dosages ranging from 5 mg/kg daily in adolescents⁶⁵ to 1000 to 1500 mg daily in adults.⁶⁶

Of the various immunosuppressants available, infliximab has been listed in numerous reports as a successful agent in both the induction and maintenance of extraintestinal manifestations of CD including MCD.^67-71 Infliximab has been reported to be effective in the treatment of penile and scrotal edema secondary to MCD that did not respond to other immunosuppressants including oral prednisolone, azathioprine, and cyclosporine.⁴³ Infliximab may be a good option to help heal draining fistulas, particularly in combination with an antibiotic such as metronidazole and ciprofloxacin, which helps to prevent abscess formation during healing.⁷² The response to infliximab has been dramatic, with resolution of cutaneous lesions after just 6 weeks in some cases.⁷³ The dosing regimen of infliximab has been suggested at 5 mg/kg administered at 0, 2, and 6 weeks, with subsequent maintenance infusions every 10 weeks,⁷⁰ or at 0, 4, and 12 weeks, with subsequent infusions every 8 weeks.⁴³

Adalimumab may be considered as an alternative to infliximab and is potentially less allergenic as a fully humanized monoclonal antibody to TNF-α, which also has been used successfully to both induce and maintain remission of moderate to severe CD.^42,74,75 Proposed dosing of adalimumab includes a loading dose of 160 mg subcutaneously on day 1, followed by an 80-mg dose 2 weeks later and a 40-mg maintenance dose every other week indefinitely.⁴⁸ Of note, adalimumab has been noted in the literature to have many potential side effects, including one particular case in which severe headaches were attributed to its use.⁵⁹ As a consequence of the headaches, the patient was switched from adalimumab to cyclosporine and responded well with no subsequent flare-ups on follow-up.

In summary, treatment of MCD depends on cutaneous location, severity, physician experience with certain antibiotics or immunosuppressants, availability of medication, and patient disposition. It seems reasonable to attempt medical management with one or more medical regimens before committing to surgical intervention. Furthermore, even with debridement, curettage, skin graft, or other surgical strategy, the patient is likely to require some period of immunosuppression to provide long-lasting remission.

Conclusion

Patients with inflammatory bowel disease often develop dermatologic sequelae, with MCD being a rare but serious process. Patients may present with a wide array of physical concerns and symptoms, many resembling other disease processes. As such, education and a high index of suspicion are needed for proper diagnosis and treatment.

Almost half of Crohn disease (CD) patients experience a dermatologic manifestation of the disease. A rare entity, metastatic CD (MCD) presents a diagnostic challenge without a high index of suspicion. Its etiology is not well defined; however, it appears to be an autoimmune response to gut antigens. Herein, we review the etiology/epidemiology, diagnostic criteria, and treatment for this uncommon condition.

Epidemiology and Clinical Characteristics of MCD

Metastatic CD was first described by Parks et al1 in 1965 and refers to a diverse collection of macroscopic dermatologic manifestations in tissue not contiguous with the gastrointestinal (GI) tract. To be classified as MCD, the tissue must demonstrate characteristic histopathologic findings, which invariably include noncaseating granulomas.

Crohn disease may affect any part of the GI tract from the mouth to anus, with a multitude of associated cutaneous manifestations having been described. The terminal ileum is the most commonly affected portion of the GI tract in CD, but the large intestine also may be involved in 55% to 80% of cases.² The incidence of non-MCD-associated anal lesions seems to correlate with intestinal involvement in that as few as 25% of patients with ileal-localized CD have anal lesions compared to nearly 80% of patients with large intestinal involvement.³

It has been estimated that 18% to 44% of patients with CD have some form of cutaneous manifestation,⁴ with MCD being a rare subcategory. As few as 100 cases have been described from 1965 to the present.⁵ The presence of MCD does not correlate well with severity of intestinal CD, and although a majority of MCD cases present after at least 6 months of GI symptoms,⁶ there are instances in which MCD presents without prior or existing evidence of intestinal CD.⁷

With regard to MCD, the term metastatic is sometimes supplanted in the literature by cutaneous to avoid any implication of cancer; however, due to a myriad of dermatologic manifestations, both terms can cause confusion. The categorization of the various types of cutaneous findings in CD is well summarized in a review by Palamaras et al8 with the following classifications: (1) granulomatous by direct extension (oral or perianal), (2) MCD lesions (genital and nongenital), (3) immune-related lesions, and (4) lesions from nutritional deficiencies. Of the cutaneous manifestations relating to CD, MCD is the least common cutaneous categorical manifestation and is further divided into subcategories of genital and nongenital lesions.⁸

The nongenital distribution of MCD is the more common variety in adults and particularly seems to affect the legs and plantar surfaces (38%), the trunk and abdomen (24%), and the face (15%).^5,9 These nongenital MCD manifestations are most commonly described as nodules, ulcerations, or erythematous to purple plaques, and less commonly described as abscesses, pustules, or papules.

The sequence of cutaneous symptoms of MCD relative to intestinal disease depends to some degree on patient age. In adults diagnosed with MCD, it has been noted that a GI flare is expected 2 months to 4 years after diagnosis; however, in children the subsequent GI flare has been noted to vary more widely from 9 months to 14 years following presentation of MCD.⁸ Furthermore, roughly 50% of children diagnosed with MCD present concomitantly with their first symptoms of a GI flare, whereas 70% of adults with MCD had been previously diagnosed with intestinal CD.⁸ In one review of 80 reported cases of MCD, 20% (16/80) had no symptoms of intestinal disease at the time of MCD diagnosis, and the majority of the asymptomatic cases were in children; interestingly, the majority of these same children were diagnosed with CD months to years later.⁹

Both the location and characteristics of cutaneous findings in MCD correlate with age.⁹ Metastatic CD has been identified in all age groups; however, lymphedema is more common in children/young adults, while nodules, ulceration, and fistulating disease are more often seen in adults.¹⁰ Affected children and adolescents with MCD range from 5 to 17 years of age, with a mean age at disease onset of 11.1 years and equal incidence in males and females.⁸ Adults with MCD range from 18 to 78 years of age, with a mean age at presentation of 38.4 years.^8,11

Concerning anatomic location of disease, adults with MCD most commonly have nodules with or without plaques on the arms and legs and less commonly in the genital area.⁸ In contrast, children with MCD are more prone to genital lesions, with up to 85% of cases including some degree of genital erythematous or nonerythematous swelling with or without induration.⁸ Genitourinary complications of CD as a broad category, however, are estimated to occur in only 5% to 20% of intestinal CD cases in both children and adults.¹²

There have been conflicting reports regarding gender predilection in MCD. Based on a review by Samitz et al¹³ of 200 cases of CD over an 18-year period, 22% of patients with CD were found to have cutaneous manifestations--presumably not MCD but rather perianal, perineal, vulvar fistulae, fissures, or abscesses--with a male to female preponderance of almost 2 to 1. A more recent review of the literature by Palamaras et al⁸ in 2008 reported that contiguous non-MCD affects adult females and children more often than adult males, with 63% adult cases being female. This review seems to be more congruent with other reports in the literature implicating that females are twice as commonly affected by MCD than males.^9,14

Pathophysiology

The etiology of MCD has not been well defined. One proposed mechanism of the distal tissue involvement of MCD is through passage of antigens to the skin with subsequent granulomatous response at the level of the dermis.¹⁰ Another proposed mechanism suggests antibody sensitization to gut antigens, possibly bacterial antigens, that then coincidentally cross-react with analogous skin antigens.^8,14 Burgdorf¹¹ supported this notion in a 1981 report in which it was suggested that the granulomatous reaction was related to deposition of immune complexes in the skin. Slater et al¹⁵ and Tatnall et al¹⁶ offered a variation of Burgdorf's notion, suggesting that it was sensitized T cells to circulating antigens that were the initiators of granuloma formation in the periphery.

An examination of MCD tissue in 1990 by Shum and Guenther¹⁷ under electron microscopy and immunofluorescence provided evidence against prior studies that purported to have identified immune complexes as the causative agents of MCD. In this study, the authors found no evidence of immune complexes in the dermis of MCD lesions. In addition, an attempt to react serum antibodies of a patient with MCD, which were postulated to have IgG, IgM, and IgA antibodies to specific gut antigens, yielded no response when reacted with the tongue, ileum, and colon tissue from a rat. As a culminant finding, the authors also noted MCD dermis tissue with granulomas without vasculitis, suggesting a T-cell mediated type IV hypersensitivity response with a secondary vasculitis from T-cell origin lymphokines and T-cell mediated monocyte activation.¹⁷

Research implicating other immunologic entities involved in the pathophysiology of CD such as β-2 integrin,¹⁸ CD14⁺ monocytes,¹⁹ and the role of the DNA repair gene MLH1 (mutL homolog 1)²⁰ have been considered but without a clearly definitive role in the manifestations of MCD.

The utility of metronidazole in the treatment of MCD has been suggested as evidence that certain bacteria in the gut may either serve as the causative antigen or may induce its formation²¹; however, the causative antigen has yet to be identified, and whether it travels distally to the skin or merely resembles a similar antigen normally present in the dermis has not yet been determined. Some research has used in situ polymerase chain reaction techniques to attempt to detect similar microbial pathogens in both the vasculature of active bowel lesions and in the skin, but to date, bacterial RNA noted to be present in the gut vasculature adjacent to CD lesions has not been detected in skin lesions.²²

Diagnosis

Physical Findings

Overall, it is estimated that roughly 56% of all MCD cases affect the external genitalia.²³ The classic appearance of MCD includes well-demarcated ulcerations in the areas of intertriginous skin folds with or without diffuse edema and tenderness to palpation.²³ Although MCD has been historically noted as having a predilection for moist skin folds, there are numerous case reports of MCD all over the body, including the face,^7,24-29 retroauricular areas,³⁰ arms and legs,^16,17,31-34 lower abdomen,^3,5 under the breasts,¹ perineum,³⁵ external genitalia,^1,9,36-40 and even the lungs⁴¹ and bladder.⁴²

As a dermatologic disease, MCD has been referred to as yet another great imitator, both on the macroscopic and microscopic levels.⁸ As such, more common causes of genital edema should be considered first and investigated based on the patient's history, physical examination, skin biopsy, lymphangiogram, ultrasound, and cystogram.⁴³ Ultrasonography and color Doppler sonography have been shown to be helpful in patients with genital involvement. This modality can evaluate not only the presence of normal testes but also intratesticular and scrotal wall fluid, especially when the physical examination reveals swelling that makes testicle palpation more difficult.⁶ Clinically, the correct diagnosis of MCD often is made through suspicion of inflammatory bowel disease based on classic symptoms and/or physical findings including abdominal pain, weight loss, bloody stool, diarrhea, perianal skin tags, and anal fissures or fistulas. Any of these GI findings should prompt an intestinal biopsy to rule out any histologic evidence of CD.

Metastatic CD affecting the vulva often presents with vulvar pain and pruritus and may clinically mimic a more benign disease such as balanitis plasmacellularis, also referred to as Zoon vulvitis.²³ Similar to MCD on any given body surface, there is dramatic variation in the macroscopic presentation of vulvar MCD, with physical examination findings ranging from bilateral diffuse, edematous, deeply macerated, red, ulcerated lesions over the vulva with lymphadenopathy to findings of bilateral vulvar pain with yellow drainage from the labia majora.²³ There have been cases of vulvar MCD that include exquisite vulvar pain but without structural abnormalities including normal uterus, cervix, adnexa, rectovaginal septum, and rectum. In these more nebulous cases of vulvar MCD, the diagnosis often is discovered incidentally when nonspecific diagnostic imaging suggests underlying CD.²³

Beyond the case-by-case variations on physical examination, the great difficulty in diagnosis, particularly in children, occurs in the absence of any GI symptoms and therefore no logical consideration of underlying CD. Consequently, there have been cases of children presenting with irritation of the vulva who were eventually diagnosed with MCD only after erroneous treatment of contact dermatitis, candidiasis, and even consideration of sexual abuse.³⁷ Because it is so rare and obscure among practicing clinicians, the diagnosis of MCD often is considered only after irritation or swelling of the external genitalia has not responded to standard therapies. If and when the diagnosis of MCD is considered in children, it has been suggested to screen patients for anorectal stricture, as case studies have found the condition to be relatively common in this subpopulation.⁴⁴

In the less common case of adults with genitourinary symptoms that suggest possible MCD, the differential diagnosis for penile or vaginal ulcers should include contact and irritant dermatitis, chronic infectious lesions (eg, hidradenitis suppurativa, actinomycosis, tuberculosis),⁴⁵ sexually transmitted ulcerative diseases (eg, chancroid, lymphogranuloma venereum, herpes genitalia, granuloma inguinale),⁴⁶ drug reactions, and even extramammary Paget disease.⁴⁷

Histologic Findings

Because MCD has so much macroscopic variation and can present anywhere on the surface of the body, formal diagnosis relies on microscopy. As an added measure of difficulty in diagnosis, one random biopsy of a suspicious segment of tissue may not contain the expected histologic findings; therefore, clinical suspicion may warrant a second biopsy.¹⁰ There have been reported cases of an adult patient without history of CD presenting with a lesion that resembled a more common pathology, such as a genital wart, and the correct diagnosis of MCD with pseudocondylomatous morphology was made only after intestinal manifestations prompted the clinician to consider such an unusual diagnosis.⁴⁸

From a histopathologic perspective, MCD is characterized by discrete, noncaseating, sarcoidlike granulomas with abundant multinucleated giant cells (Langhans giant cells) in the superficial dermis (papillary), deep dermis (reticular), and adipose tissue (Figure).^8,17 In the presence of concomitant intestinal disease, the granulomas of both the intestinal and dermal tissues should share the same microscopic characteristics.⁸ In addition, copious neutrophils and granulomas surrounding the microvasculature have been described,³⁴ as well as general lymphocyte and plasma cell infiltrate.⁴⁵ Some histologic samples have included collagen degeneration termed necrobiosis in the middle dermal layer as another variable finding in MCD.^14,34

On microscopy, it has been reported that use of Verhoeff-van Gieson staining may be helpful to highlight the presence of neutrophil obstruction within the dermal vasculature, particularly the arterial lumen, as well as to aid in highlighting swelling of the endothelium with fragmentation of the internal elastic lamina.¹⁷ Although not part of the routine diagnosis, electron microscopy of MCD tissue samples have confirmed hypertrophy of the endothelial cells composing the capillaries with resulting extravasation of fibrin, red blood cells, lymphocytes, and epithelioid histiocytes.¹⁷ Observation of tissue under direct immunofluorescence has been less helpful, as it has shown only nonspecific fibrinogen deposition within the dermis and dermal vessels.¹⁷

In an article on treatment of MCD, Escher et al⁴³ reinforced that the macroscopic findings of MCD are diverse, and the microscopic findings characteristic of MCD also can be mimicked by other etiologies such as sarcoidosis, tuberculosis, fungal infections, lymphogranuloma venereum, leishmaniasis, and connective tissue disorders.⁴³ As such, the workup to rule out infectious, anatomic, and autoimmune etiologies should be diverse. Often, the workup for MCD will include special stains such as Ziehl-Neelsen stain to rule out Mycobacterium tuberculosis and acid-fast bacilli and Fite stain to consider atypical mycobacteria. Other tests such as tissue culture, chest radiograph, tuberculin skin test (Mantoux test), IFN-γ release assay, or polarized light microscopy may rule out infectious etiologies.^9,49 Serologic testing might include VDRL test, Treponema pallidum hemagglutination assay, hepatitis B, hepatitis C, and human immunodeficiency virus.⁵

Crohn disease is characterized histologically by sarcoidlike noncaseating granulomas, and as such, it is important to differentiate MCD from sarcoidosis prior to histologic analysis. Sarcoidosis also can be considered much less likely with a normal chest radiograph and in the absence of increased serum calcium and angiotensin-converting enzyme levels.⁷ The differentiation of sarcoidosis from MCD on the microscopic scale is subtle but is sometimes facilitated in the presence of an ulcerated epidermis or lymphocytic/eosinophilic infiltrate and edema within the dermis, all suggestive of MCD.¹⁴

Metastatic CD also should be differentiated from erythema nodosum and pyoderma gangrenosum, which are among the most common cutaneous findings associated with CD.¹⁴ Pyoderma gangrenosum can be distinguished histologically by identifying copious neutrophilic infiltrate with pseudoepitheliomatous hyperplasia.⁵⁰

Treatment

Because MCD is relatively rare, there are no known randomized trials suggesting a particular medical or surgical treatment. In a review of perineal MCD from 2007, the 40-year-old recommendation by Moutain³ opting for surgical debridement versus medical management still resonates, particularly for perineal disease, as an effective measure in all but the mildest of presentations.⁵¹ However, recent case reports also suggest that the tumor necrosis factor α (TNF-α) inhibitors such as infliximab and adalimumab should be considered prior to surgery even with severe perineal MCD.⁵¹ Moreover, even if medical management with TNF-α inhibitors or some combination of immunosuppressants and antibiotics does not eradicate the disease, it often helps reduce the size of the ulcers prior to surgery.⁵² With a limited understanding of MCD, one might think that removal of the affected bowel would eliminate cutaneous disease, but it has been shown that this strategy is not effective.^53,54

The composition and location of the particular lesion affects the trajectory of treatment. For example, MCD manifesting as local ulcers and plaques has been described as responding well to topical and intralesional steroids.^10,55,56 In the case of penile swelling and/or phimosis, circumcision has been helpful to improve the patient's ability to void as well as to attain and maintain erection.¹⁰ In the case of scrotal swelling secondary to MCD, early treatment (ie, within 4 to 6 months) with oral steroids and/or metronidazole is likely beneficial to prevent refractory edematous organization of the tissue.⁵⁷

As a general rule, an effective treatment will include a combination of an immunosuppressant, antibiotic therapy, and sometimes surgery. The most commonly used immunosuppressant agents include topical or intralesional steroids, infliximab,^43,58 cyclosporine A,^59,60 dapsone, minocycline, thalidomide, methotrexate, mycophenolate mofetil, sulfasalazine, azathioprine, tacrolimus, and 6-mercaptopurine.⁴ Steroids have been the conventional treatment of extraintestinal manifestations of CD⁶¹; however, perineal CD has been poorly controlled with systemic steroids.⁶² If steroids are found not to be effective, sometimes agents such as dapsone or thalidomide are considered. One case report noted stabilization of MCD penile ulcers with oral thalidomide 300 mg once daily, oral minocycline 100 mg once daily, and topical tacrolimus 0.3% with benzocaine twice daily with continuation of prednisolone and methotrexate as parts of previously unsuccessful regimen.⁵²

Metronidazole is perhaps the most commonly used antibiotic, having been a component of many successful regimens.^4,63 For example, a 27-year-old patient with MCD presenting as a nonhealing ulcerative lesion in the subcoronal area of the penis and scrotum was treated successfully with a 6-month course of mesalamine, prednisone, and metronidazole.⁴⁵ Another case report of vulvar MCD reported initial success with intravenous methylprednisolone, ciprofloxacin, and metronidazole.²³ The primary limitation of metronidazole is that subsequent tapering of the dose seems to result in recurrence of disease.⁶⁴ Consequently, patients must remain on the antibiotic for an indeterminate course, with dosages ranging from 5 mg/kg daily in adolescents⁶⁵ to 1000 to 1500 mg daily in adults.⁶⁶

Of the various immunosuppressants available, infliximab has been listed in numerous reports as a successful agent in both the induction and maintenance of extraintestinal manifestations of CD including MCD.^67-71 Infliximab has been reported to be effective in the treatment of penile and scrotal edema secondary to MCD that did not respond to other immunosuppressants including oral prednisolone, azathioprine, and cyclosporine.⁴³ Infliximab may be a good option to help heal draining fistulas, particularly in combination with an antibiotic such as metronidazole and ciprofloxacin, which helps to prevent abscess formation during healing.⁷² The response to infliximab has been dramatic, with resolution of cutaneous lesions after just 6 weeks in some cases.⁷³ The dosing regimen of infliximab has been suggested at 5 mg/kg administered at 0, 2, and 6 weeks, with subsequent maintenance infusions every 10 weeks,⁷⁰ or at 0, 4, and 12 weeks, with subsequent infusions every 8 weeks.⁴³

Adalimumab may be considered as an alternative to infliximab and is potentially less allergenic as a fully humanized monoclonal antibody to TNF-α, which also has been used successfully to both induce and maintain remission of moderate to severe CD.^42,74,75 Proposed dosing of adalimumab includes a loading dose of 160 mg subcutaneously on day 1, followed by an 80-mg dose 2 weeks later and a 40-mg maintenance dose every other week indefinitely.⁴⁸ Of note, adalimumab has been noted in the literature to have many potential side effects, including one particular case in which severe headaches were attributed to its use.⁵⁹ As a consequence of the headaches, the patient was switched from adalimumab to cyclosporine and responded well with no subsequent flare-ups on follow-up.

In summary, treatment of MCD depends on cutaneous location, severity, physician experience with certain antibiotics or immunosuppressants, availability of medication, and patient disposition. It seems reasonable to attempt medical management with one or more medical regimens before committing to surgical intervention. Furthermore, even with debridement, curettage, skin graft, or other surgical strategy, the patient is likely to require some period of immunosuppression to provide long-lasting remission.

Conclusion

Patients with inflammatory bowel disease often develop dermatologic sequelae, with MCD being a rare but serious process. Patients may present with a wide array of physical concerns and symptoms, many resembling other disease processes. As such, education and a high index of suspicion are needed for proper diagnosis and treatment.

Almost half of Crohn disease (CD) patients experience a dermatologic manifestation of the disease. A rare entity, metastatic CD (MCD) presents a diagnostic challenge without a high index of suspicion. Its etiology is not well defined; however, it appears to be an autoimmune response to gut antigens. Herein, we review the etiology/epidemiology, diagnostic criteria, and treatment for this uncommon condition.

Epidemiology and Clinical Characteristics of MCD

Metastatic CD was first described by Parks et al1 in 1965 and refers to a diverse collection of macroscopic dermatologic manifestations in tissue not contiguous with the gastrointestinal (GI) tract. To be classified as MCD, the tissue must demonstrate characteristic histopathologic findings, which invariably include noncaseating granulomas.

Crohn disease may affect any part of the GI tract from the mouth to anus, with a multitude of associated cutaneous manifestations having been described. The terminal ileum is the most commonly affected portion of the GI tract in CD, but the large intestine also may be involved in 55% to 80% of cases.² The incidence of non-MCD-associated anal lesions seems to correlate with intestinal involvement in that as few as 25% of patients with ileal-localized CD have anal lesions compared to nearly 80% of patients with large intestinal involvement.³

It has been estimated that 18% to 44% of patients with CD have some form of cutaneous manifestation,⁴ with MCD being a rare subcategory. As few as 100 cases have been described from 1965 to the present.⁵ The presence of MCD does not correlate well with severity of intestinal CD, and although a majority of MCD cases present after at least 6 months of GI symptoms,⁶ there are instances in which MCD presents without prior or existing evidence of intestinal CD.⁷

With regard to MCD, the term metastatic is sometimes supplanted in the literature by cutaneous to avoid any implication of cancer; however, due to a myriad of dermatologic manifestations, both terms can cause confusion. The categorization of the various types of cutaneous findings in CD is well summarized in a review by Palamaras et al8 with the following classifications: (1) granulomatous by direct extension (oral or perianal), (2) MCD lesions (genital and nongenital), (3) immune-related lesions, and (4) lesions from nutritional deficiencies. Of the cutaneous manifestations relating to CD, MCD is the least common cutaneous categorical manifestation and is further divided into subcategories of genital and nongenital lesions.⁸

The nongenital distribution of MCD is the more common variety in adults and particularly seems to affect the legs and plantar surfaces (38%), the trunk and abdomen (24%), and the face (15%).^5,9 These nongenital MCD manifestations are most commonly described as nodules, ulcerations, or erythematous to purple plaques, and less commonly described as abscesses, pustules, or papules.

The sequence of cutaneous symptoms of MCD relative to intestinal disease depends to some degree on patient age. In adults diagnosed with MCD, it has been noted that a GI flare is expected 2 months to 4 years after diagnosis; however, in children the subsequent GI flare has been noted to vary more widely from 9 months to 14 years following presentation of MCD.⁸ Furthermore, roughly 50% of children diagnosed with MCD present concomitantly with their first symptoms of a GI flare, whereas 70% of adults with MCD had been previously diagnosed with intestinal CD.⁸ In one review of 80 reported cases of MCD, 20% (16/80) had no symptoms of intestinal disease at the time of MCD diagnosis, and the majority of the asymptomatic cases were in children; interestingly, the majority of these same children were diagnosed with CD months to years later.⁹

Both the location and characteristics of cutaneous findings in MCD correlate with age.⁹ Metastatic CD has been identified in all age groups; however, lymphedema is more common in children/young adults, while nodules, ulceration, and fistulating disease are more often seen in adults.¹⁰ Affected children and adolescents with MCD range from 5 to 17 years of age, with a mean age at disease onset of 11.1 years and equal incidence in males and females.⁸ Adults with MCD range from 18 to 78 years of age, with a mean age at presentation of 38.4 years.^8,11

Concerning anatomic location of disease, adults with MCD most commonly have nodules with or without plaques on the arms and legs and less commonly in the genital area.⁸ In contrast, children with MCD are more prone to genital lesions, with up to 85% of cases including some degree of genital erythematous or nonerythematous swelling with or without induration.⁸ Genitourinary complications of CD as a broad category, however, are estimated to occur in only 5% to 20% of intestinal CD cases in both children and adults.¹²

There have been conflicting reports regarding gender predilection in MCD. Based on a review by Samitz et al¹³ of 200 cases of CD over an 18-year period, 22% of patients with CD were found to have cutaneous manifestations--presumably not MCD but rather perianal, perineal, vulvar fistulae, fissures, or abscesses--with a male to female preponderance of almost 2 to 1. A more recent review of the literature by Palamaras et al⁸ in 2008 reported that contiguous non-MCD affects adult females and children more often than adult males, with 63% adult cases being female. This review seems to be more congruent with other reports in the literature implicating that females are twice as commonly affected by MCD than males.^9,14

Pathophysiology

The etiology of MCD has not been well defined. One proposed mechanism of the distal tissue involvement of MCD is through passage of antigens to the skin with subsequent granulomatous response at the level of the dermis.¹⁰ Another proposed mechanism suggests antibody sensitization to gut antigens, possibly bacterial antigens, that then coincidentally cross-react with analogous skin antigens.^8,14 Burgdorf¹¹ supported this notion in a 1981 report in which it was suggested that the granulomatous reaction was related to deposition of immune complexes in the skin. Slater et al¹⁵ and Tatnall et al¹⁶ offered a variation of Burgdorf's notion, suggesting that it was sensitized T cells to circulating antigens that were the initiators of granuloma formation in the periphery.

An examination of MCD tissue in 1990 by Shum and Guenther¹⁷ under electron microscopy and immunofluorescence provided evidence against prior studies that purported to have identified immune complexes as the causative agents of MCD. In this study, the authors found no evidence of immune complexes in the dermis of MCD lesions. In addition, an attempt to react serum antibodies of a patient with MCD, which were postulated to have IgG, IgM, and IgA antibodies to specific gut antigens, yielded no response when reacted with the tongue, ileum, and colon tissue from a rat. As a culminant finding, the authors also noted MCD dermis tissue with granulomas without vasculitis, suggesting a T-cell mediated type IV hypersensitivity response with a secondary vasculitis from T-cell origin lymphokines and T-cell mediated monocyte activation.¹⁷

Research implicating other immunologic entities involved in the pathophysiology of CD such as β-2 integrin,¹⁸ CD14⁺ monocytes,¹⁹ and the role of the DNA repair gene MLH1 (mutL homolog 1)²⁰ have been considered but without a clearly definitive role in the manifestations of MCD.

The utility of metronidazole in the treatment of MCD has been suggested as evidence that certain bacteria in the gut may either serve as the causative antigen or may induce its formation²¹; however, the causative antigen has yet to be identified, and whether it travels distally to the skin or merely resembles a similar antigen normally present in the dermis has not yet been determined. Some research has used in situ polymerase chain reaction techniques to attempt to detect similar microbial pathogens in both the vasculature of active bowel lesions and in the skin, but to date, bacterial RNA noted to be present in the gut vasculature adjacent to CD lesions has not been detected in skin lesions.²²

Diagnosis

Physical Findings

Overall, it is estimated that roughly 56% of all MCD cases affect the external genitalia.²³ The classic appearance of MCD includes well-demarcated ulcerations in the areas of intertriginous skin folds with or without diffuse edema and tenderness to palpation.²³ Although MCD has been historically noted as having a predilection for moist skin folds, there are numerous case reports of MCD all over the body, including the face,^7,24-29 retroauricular areas,³⁰ arms and legs,^16,17,31-34 lower abdomen,^3,5 under the breasts,¹ perineum,³⁵ external genitalia,^1,9,36-40 and even the lungs⁴¹ and bladder.⁴²

As a dermatologic disease, MCD has been referred to as yet another great imitator, both on the macroscopic and microscopic levels.⁸ As such, more common causes of genital edema should be considered first and investigated based on the patient's history, physical examination, skin biopsy, lymphangiogram, ultrasound, and cystogram.⁴³ Ultrasonography and color Doppler sonography have been shown to be helpful in patients with genital involvement. This modality can evaluate not only the presence of normal testes but also intratesticular and scrotal wall fluid, especially when the physical examination reveals swelling that makes testicle palpation more difficult.⁶ Clinically, the correct diagnosis of MCD often is made through suspicion of inflammatory bowel disease based on classic symptoms and/or physical findings including abdominal pain, weight loss, bloody stool, diarrhea, perianal skin tags, and anal fissures or fistulas. Any of these GI findings should prompt an intestinal biopsy to rule out any histologic evidence of CD.

Metastatic CD affecting the vulva often presents with vulvar pain and pruritus and may clinically mimic a more benign disease such as balanitis plasmacellularis, also referred to as Zoon vulvitis.²³ Similar to MCD on any given body surface, there is dramatic variation in the macroscopic presentation of vulvar MCD, with physical examination findings ranging from bilateral diffuse, edematous, deeply macerated, red, ulcerated lesions over the vulva with lymphadenopathy to findings of bilateral vulvar pain with yellow drainage from the labia majora.²³ There have been cases of vulvar MCD that include exquisite vulvar pain but without structural abnormalities including normal uterus, cervix, adnexa, rectovaginal septum, and rectum. In these more nebulous cases of vulvar MCD, the diagnosis often is discovered incidentally when nonspecific diagnostic imaging suggests underlying CD.²³

Beyond the case-by-case variations on physical examination, the great difficulty in diagnosis, particularly in children, occurs in the absence of any GI symptoms and therefore no logical consideration of underlying CD. Consequently, there have been cases of children presenting with irritation of the vulva who were eventually diagnosed with MCD only after erroneous treatment of contact dermatitis, candidiasis, and even consideration of sexual abuse.³⁷ Because it is so rare and obscure among practicing clinicians, the diagnosis of MCD often is considered only after irritation or swelling of the external genitalia has not responded to standard therapies. If and when the diagnosis of MCD is considered in children, it has been suggested to screen patients for anorectal stricture, as case studies have found the condition to be relatively common in this subpopulation.⁴⁴

In the less common case of adults with genitourinary symptoms that suggest possible MCD, the differential diagnosis for penile or vaginal ulcers should include contact and irritant dermatitis, chronic infectious lesions (eg, hidradenitis suppurativa, actinomycosis, tuberculosis),⁴⁵ sexually transmitted ulcerative diseases (eg, chancroid, lymphogranuloma venereum, herpes genitalia, granuloma inguinale),⁴⁶ drug reactions, and even extramammary Paget disease.⁴⁷

Histologic Findings

Because MCD has so much macroscopic variation and can present anywhere on the surface of the body, formal diagnosis relies on microscopy. As an added measure of difficulty in diagnosis, one random biopsy of a suspicious segment of tissue may not contain the expected histologic findings; therefore, clinical suspicion may warrant a second biopsy.¹⁰ There have been reported cases of an adult patient without history of CD presenting with a lesion that resembled a more common pathology, such as a genital wart, and the correct diagnosis of MCD with pseudocondylomatous morphology was made only after intestinal manifestations prompted the clinician to consider such an unusual diagnosis.⁴⁸

From a histopathologic perspective, MCD is characterized by discrete, noncaseating, sarcoidlike granulomas with abundant multinucleated giant cells (Langhans giant cells) in the superficial dermis (papillary), deep dermis (reticular), and adipose tissue (Figure).^8,17 In the presence of concomitant intestinal disease, the granulomas of both the intestinal and dermal tissues should share the same microscopic characteristics.⁸ In addition, copious neutrophils and granulomas surrounding the microvasculature have been described,³⁴ as well as general lymphocyte and plasma cell infiltrate.⁴⁵ Some histologic samples have included collagen degeneration termed necrobiosis in the middle dermal layer as another variable finding in MCD.^14,34

On microscopy, it has been reported that use of Verhoeff-van Gieson staining may be helpful to highlight the presence of neutrophil obstruction within the dermal vasculature, particularly the arterial lumen, as well as to aid in highlighting swelling of the endothelium with fragmentation of the internal elastic lamina.¹⁷ Although not part of the routine diagnosis, electron microscopy of MCD tissue samples have confirmed hypertrophy of the endothelial cells composing the capillaries with resulting extravasation of fibrin, red blood cells, lymphocytes, and epithelioid histiocytes.¹⁷ Observation of tissue under direct immunofluorescence has been less helpful, as it has shown only nonspecific fibrinogen deposition within the dermis and dermal vessels.¹⁷

In an article on treatment of MCD, Escher et al⁴³ reinforced that the macroscopic findings of MCD are diverse, and the microscopic findings characteristic of MCD also can be mimicked by other etiologies such as sarcoidosis, tuberculosis, fungal infections, lymphogranuloma venereum, leishmaniasis, and connective tissue disorders.⁴³ As such, the workup to rule out infectious, anatomic, and autoimmune etiologies should be diverse. Often, the workup for MCD will include special stains such as Ziehl-Neelsen stain to rule out Mycobacterium tuberculosis and acid-fast bacilli and Fite stain to consider atypical mycobacteria. Other tests such as tissue culture, chest radiograph, tuberculin skin test (Mantoux test), IFN-γ release assay, or polarized light microscopy may rule out infectious etiologies.^9,49 Serologic testing might include VDRL test, Treponema pallidum hemagglutination assay, hepatitis B, hepatitis C, and human immunodeficiency virus.⁵

Crohn disease is characterized histologically by sarcoidlike noncaseating granulomas, and as such, it is important to differentiate MCD from sarcoidosis prior to histologic analysis. Sarcoidosis also can be considered much less likely with a normal chest radiograph and in the absence of increased serum calcium and angiotensin-converting enzyme levels.⁷ The differentiation of sarcoidosis from MCD on the microscopic scale is subtle but is sometimes facilitated in the presence of an ulcerated epidermis or lymphocytic/eosinophilic infiltrate and edema within the dermis, all suggestive of MCD.¹⁴

Metastatic CD also should be differentiated from erythema nodosum and pyoderma gangrenosum, which are among the most common cutaneous findings associated with CD.¹⁴ Pyoderma gangrenosum can be distinguished histologically by identifying copious neutrophilic infiltrate with pseudoepitheliomatous hyperplasia.⁵⁰

Treatment

Because MCD is relatively rare, there are no known randomized trials suggesting a particular medical or surgical treatment. In a review of perineal MCD from 2007, the 40-year-old recommendation by Moutain³ opting for surgical debridement versus medical management still resonates, particularly for perineal disease, as an effective measure in all but the mildest of presentations.⁵¹ However, recent case reports also suggest that the tumor necrosis factor α (TNF-α) inhibitors such as infliximab and adalimumab should be considered prior to surgery even with severe perineal MCD.⁵¹ Moreover, even if medical management with TNF-α inhibitors or some combination of immunosuppressants and antibiotics does not eradicate the disease, it often helps reduce the size of the ulcers prior to surgery.⁵² With a limited understanding of MCD, one might think that removal of the affected bowel would eliminate cutaneous disease, but it has been shown that this strategy is not effective.^53,54

The composition and location of the particular lesion affects the trajectory of treatment. For example, MCD manifesting as local ulcers and plaques has been described as responding well to topical and intralesional steroids.^10,55,56 In the case of penile swelling and/or phimosis, circumcision has been helpful to improve the patient's ability to void as well as to attain and maintain erection.¹⁰ In the case of scrotal swelling secondary to MCD, early treatment (ie, within 4 to 6 months) with oral steroids and/or metronidazole is likely beneficial to prevent refractory edematous organization of the tissue.⁵⁷

As a general rule, an effective treatment will include a combination of an immunosuppressant, antibiotic therapy, and sometimes surgery. The most commonly used immunosuppressant agents include topical or intralesional steroids, infliximab,^43,58 cyclosporine A,^59,60 dapsone, minocycline, thalidomide, methotrexate, mycophenolate mofetil, sulfasalazine, azathioprine, tacrolimus, and 6-mercaptopurine.⁴ Steroids have been the conventional treatment of extraintestinal manifestations of CD⁶¹; however, perineal CD has been poorly controlled with systemic steroids.⁶² If steroids are found not to be effective, sometimes agents such as dapsone or thalidomide are considered. One case report noted stabilization of MCD penile ulcers with oral thalidomide 300 mg once daily, oral minocycline 100 mg once daily, and topical tacrolimus 0.3% with benzocaine twice daily with continuation of prednisolone and methotrexate as parts of previously unsuccessful regimen.⁵²

Metronidazole is perhaps the most commonly used antibiotic, having been a component of many successful regimens.^4,63 For example, a 27-year-old patient with MCD presenting as a nonhealing ulcerative lesion in the subcoronal area of the penis and scrotum was treated successfully with a 6-month course of mesalamine, prednisone, and metronidazole.⁴⁵ Another case report of vulvar MCD reported initial success with intravenous methylprednisolone, ciprofloxacin, and metronidazole.²³ The primary limitation of metronidazole is that subsequent tapering of the dose seems to result in recurrence of disease.⁶⁴ Consequently, patients must remain on the antibiotic for an indeterminate course, with dosages ranging from 5 mg/kg daily in adolescents⁶⁵ to 1000 to 1500 mg daily in adults.⁶⁶

Of the various immunosuppressants available, infliximab has been listed in numerous reports as a successful agent in both the induction and maintenance of extraintestinal manifestations of CD including MCD.^67-71 Infliximab has been reported to be effective in the treatment of penile and scrotal edema secondary to MCD that did not respond to other immunosuppressants including oral prednisolone, azathioprine, and cyclosporine.⁴³ Infliximab may be a good option to help heal draining fistulas, particularly in combination with an antibiotic such as metronidazole and ciprofloxacin, which helps to prevent abscess formation during healing.⁷² The response to infliximab has been dramatic, with resolution of cutaneous lesions after just 6 weeks in some cases.⁷³ The dosing regimen of infliximab has been suggested at 5 mg/kg administered at 0, 2, and 6 weeks, with subsequent maintenance infusions every 10 weeks,⁷⁰ or at 0, 4, and 12 weeks, with subsequent infusions every 8 weeks.⁴³

Adalimumab may be considered as an alternative to infliximab and is potentially less allergenic as a fully humanized monoclonal antibody to TNF-α, which also has been used successfully to both induce and maintain remission of moderate to severe CD.^42,74,75 Proposed dosing of adalimumab includes a loading dose of 160 mg subcutaneously on day 1, followed by an 80-mg dose 2 weeks later and a 40-mg maintenance dose every other week indefinitely.⁴⁸ Of note, adalimumab has been noted in the literature to have many potential side effects, including one particular case in which severe headaches were attributed to its use.⁵⁹ As a consequence of the headaches, the patient was switched from adalimumab to cyclosporine and responded well with no subsequent flare-ups on follow-up.

In summary, treatment of MCD depends on cutaneous location, severity, physician experience with certain antibiotics or immunosuppressants, availability of medication, and patient disposition. It seems reasonable to attempt medical management with one or more medical regimens before committing to surgical intervention. Furthermore, even with debridement, curettage, skin graft, or other surgical strategy, the patient is likely to require some period of immunosuppression to provide long-lasting remission.

Conclusion

Patients with inflammatory bowel disease often develop dermatologic sequelae, with MCD being a rare but serious process. Patients may present with a wide array of physical concerns and symptoms, many resembling other disease processes. As such, education and a high index of suspicion are needed for proper diagnosis and treatment.

Since publication of initial findings of the Women’s Health Initiative (WHI) in 2002, use of systemic menopausal hormone therapy (HT) has declined by some 80% among US women.¹ Against this backdrop, this year’s Menopause Update highlights the “hot off the press” updated position statement on menopausal HT from The North American Menopause Society (NAMS), summarized by Dr. JoAnn V. Pinkerton. Although this guidance is chock full of practical, evidence-based guidance, the take-home message that Dr. Pinkerton and I would like to leave readers of OBG Management with is that for women with bothersome menopausal symptoms aged in their 50s or within 10 years of the onset of menopause who are free of contraindications, use of systemic HT is appropriate.

Related Article:
Dr. Andrew M. Kaunitz on prescribing systemic HT to older women

Although menopausal vasomotor and related symptoms improve as women age, in untreated women, vulvovaginal atrophy (VVA, also known as genitourinary syndrome of menopause, or GSM) tends to progress, causing vaginal dryness and sexual dysfunction, among other symptoms. When symptomatic GSM represents the only indication for treatment, low-dose local vaginal estrogen, ospemifene, or dehydroepiandrosterone (DHEA; prasterone) is safe and effective. However, as with systemic HT, specific treatments for GSM are substantially underutilized.² The current package labeling for low-dose vaginal estrogen deters many appropriate candidates from using this safe, effective treatment. In this Update, Dr. JoAnn E. Manson reviews the rationale for updating this labeling as well as recent efforts to accomplish the task.

Read about updated NAMS guidelines on HT

Guidelines on HT have been updated by The North American Menopause Society

The 2017 hormone therapy position statement of The North American Menopause Society [published online ahead of print June 2017]. Menopause.

The North American Menopause Society Hormone Therapy (HT) Position Statement Advisory Panel, composed of more than 20 experts in menopausal women's HT, including clinicians, researchers, and epidemiologists, reviewed the 2012 HT Position Statement, evaluated prior and new literature and used levels of evidence to identify the quality of the evidence and strength of the recommendations and to find consensus for the guidelines. The following information comes from the NAMS 2017 Hormone Therapy Position Statement.³

What are the major findings?

HT is the most effective treatment for vasomotor symptoms (VMS) and GSM and has been shown to prevent bone loss and fracture. Risks of HT may differ for women depending on type, dose, duration, route of administration, and timing of initiation and whether or not a progestogen is needed. Treatment should be individualized using the best available evidence to maximize benefits and minimize risks, with periodic reevaluation about benefits and risks of continuing or discontinuing HT.

For women who are younger than age 60 or within 10 years of menopause and have no contraindication, the clearest benefit of HT is for the treatment of VMS and prevention of bone loss in those at elevated risk.

The clinical guidelines were presented to NAMS audience at the 2016 annual clinical meeting, where NAMS recommended "determining the most appropriate type, dose, formulation, and duration of HT."⁴

When to initiate HT and duration of use

In its now-published 2017 guidelines on HT, NAMS affirms the safety and efficacy of HT for symptomatic menopausal women or those at high risk for bone loss who are under age 60 or within 10 years of menopause. NAMS encourages practitioners to employ shared decision making with their patients to find the appropriate type, dose, formulation, and duration of HT, making individualized decisions based on evidence-based information, the unique health risks of women, and with periodic reassessment.

In the clinical guidelines presented in the 2016 NAMS annual meeting,⁴ key recommendations taken from the 2017 Hormone Therapy Position Statement³ include the following: For women who are aged younger than 60 years or within 10 years of menopause and have no contraindications, the benefit/risk ratio appears favorable for treatment of bothersome VMS and in those at elevated risk for bone loss or fracture.

For women who initiate HT more than 10 years from menopause or after age 60, this benefit/risk ratio appears less favorable because of greater absolute risks of coronary heart disease, stroke, venous thromboembolism, and dementia.

What about extended use of hormone therapy? There is no evidence to support routine discontinuation of HT after age 65. Decisions about longer durations of HT should be individualized and considered for indications such as persistent VMS or bone loss, with shared decision making, documentation, and periodic reevaluation. Longer duration is more favorable for estrogen therapy than for estrogen-progestin therapy, based on the Women's Health Initiative (WHI) randomized controlled trials.⁵

What about only vaginal symptoms? For bothersome GSM not relieved with over-the-counter therapies and without indications for use of systemic HT, low-dose vaginal estrogen therapy or other therapies are recommended and can be continued as long as indicated since there is minimal systemic absorption of estrogen, with serum levels remaining within the normal postmenopausal range.^6,7 For women with estrogen sensitive cancer, oncologists should be included in decision making, particularly for women on aromatase inhibitors.

Considerations for special populations Early menopause. For women with hypoestrogenism, primary ovarian insufficiency, or premature surgical menopause without contraindications, HT is recommended until at least the median age of menopause (52 years), as studies suggest that benefits outweigh the risks for effects on bone, heart, cognition, GSM, sexual function, and mood.⁸

Family history of breast cancer. Observational evidence suggests that use of HT does not further alter the risk for breast cancer in women with a family history of breast cancer. Family history is one risk, among others, that should be assessed when counseling women regarding HT.

Women who are BRCA-positive without breast cancer. For women who are BRCA-positive (higher genetic risk of breast cancer, primarily estrogen-receptor-negative), and have undergone surgical menopause (bilateral salpingo-oophorectomy), the benefits of estrogen to decrease health risks caused by premature loss of estrogen need to be considered on an individual basis.⁹ On the basis of limited observational studies, consider offering systemic HT until the median age of menopause (52 years) with longer use individualized.³

Related Article:
Is menopausal hormone therapy safe when your patient carries a BRCA mutation?

Survivors of endometrial and breast cancer with bothersome VMS. For women with prior estrogen-sensitive cancers, non-HTs should be considered first, particularly those agents studied through randomized controlled trials in this population and found to be effective. If systemic estrogen is considered for persistent symptoms after non-HT or complementary options have been unsuccessful, decisions should be made for compelling reasons and after detailed counseling, with shared decision making and in conjunction with their oncologist.³ 

Bothersome GSM. On the basis of limited observational data, there appears to be minimal to no demonstrated elevation in risk for recurrence of endometrial or breast cancer using low-dose vaginal estrogen,^3,10 but decisions should be made in conjunction with an oncologist.

Related Article:
Focus on treating genital atrophy symptoms
 

The importance of relaying the new guidelines to patients

It is important for clinicians to talk to women about their menopausal symptoms and their options for relief of symptoms or prevention of bone loss. Discussion should take into account age and time from menopause, include evidence-based information^11-13 about benefits and risks of different types of therapy, and employ shared decision making to choose the most appropriate therapy to maximize benefits and minimize risks for the individual woman.

Following the WHI initial release in 2002, both women and providers became fearful of HT and believed media hype and celebrities that compounded bioidentical HT was safer than FDA-approved HTs. However, compounded products lack safety and efficacy data, are not monitored or regulated by the FDA, and have unique risks associated with compounding, including concerns about sterility, impurities, and overdosing or underdosing, which could increase cancer risk.³

Read about modifying low-dose vaginal estrogen’s black box warning

Physicians continue to underwhelmingly prescribe low-dose vaginal estrogen for GSM 

Kingsberg SA, Krychman M, Graham S, Bernick B, Mirkin S. The Women's EMPOWER survey: identifying women's perceptions on vulvar and vaginal atrophy and its treatment. J Sex Med. 2017;14(3):413-424.

GSM is seriously underrecognized and undertreated.^2,8,14 It has a major impact on women's lives--a silent epidemic affecting women's quality of life, sexual health, interpersonal relationships, and even physical health in terms of increased risk of urinary tract infections and urinary symptoms. Unfortunately, patients are reluctant to mention the problem to their clinicians, and they do not clearly recognize it as a medical condition that has available treatment options. Clinicians also rarely receive adequate training in the management of this condition and how to discuss it with their patients. Given busy schedules and time constraints, addressing this topic often falls through the cracks, representing a missed opportunity for helping our patients with safe and effective treatments. In a recent study by Kingsberg and colleagues, an astoundingly low percentageof women with GSM symptoms received treatment. 

Details of the study

The study authors evaluated women's perceptions of GSM and available treatment options. US women aged 45 and older who reported GSM symptoms were surveyed. Of 1,858 women with a median age of 58 (range, 45-90), the study authors found that 50% had never used any treatment; 25% used over-the-counter medications; 18% were former users of GSM treatments; and 7% currently used prescribed GSM therapies.

When GSM was discussed, women were more likely than their clinicians to initiate the conversation. The main reason for women not mentioning their symptoms was the perception that GSM symptoms were a natural and inevitable part of aging. Hormonal products were perceived by women as having several downsides, including risk of systemic absorption, messiness of local creams, and the need to reuse an applicator. Overall, clinicians recommended vaginal estrogen therapy to only 23% and oral HTs to 18% of women.

The results of the study are consistent with results of earlier surveys of menopausal women. Although the survey included nearly 2,000 women, it has the potential for selection biases inherent to most Internet-based surveys. In addition, the respondents tended to be white and have higher socieconomic status, with limited representation from other groups.

Calls for the current boxed warning to be revised

GSM is highly prevalent among postmenopausal women; the condition has adverse effects on quality of life and sexual health.^2,8,14 Safe and effective treatments are available but are underutilized.^1,8,15,16 A current boxed warning appears on low-dose vaginal estrogen--class labeling that appears on all medications in the class of estrogen or HT, regardless of dose or route of administration. These warnings are based on findings from the WHI and other studies of systemic estrogen or estrogen plus progestin, which demonstrated a complex pattern of risks and benefits of HT (including increased risk of venous thrombosis or pulmonary embolism, stroke, and breast cancer [with estrogen plus progestin]).

These findings, however, do not appear to be relevant to low-dose vaginal estrogen, given minimal if any systemic absorption and much lower blood levels of hormones than found with systemic HT. Blood levels of estradiol with low-dose vaginal estrogen remain in the normal postmenopausal range, compared to several-fold elevations in hormone levels with systemic HT.^8,15,16 Additionally, observational studies of low-dose vaginal estrogen, as well as short-term randomized clinical trials, show no evidence of an increased risk of venous thromboembolic events, heart disease, stroke, breast cancer, or dementia--the listed possible adverse effects in the boxed warning. The current warning is based on extrapolating findings from systemic HT, which is inappropriate and not evidence-based for low-dose vaginal estrogen.¹⁵

The inappropriate boxed warning contributes to the problem of undertreatment of GSM in women by discouraging clinicians from prescribing the medication and dissuading patients from taking it even after purchase. Testimonials from many clinicians caring for these women have underscored that women will fill their prescription, but after seeing the boxed warning will often become alarmed and decide not to take the medication. Clinicians reported that patients often say at their next appointment: "No, I never took it. I got very scared when I saw the boxed warning." As a result, clinicians often have to spend a great deal of time explaining the limitations of, and lack of evidence for, the boxed warning on low-dose vaginal estrogen.

Related Article:
2016 Update on menopause
 

Recommended label revisions

A modified label, without a boxed warning, would be safer for women because the key messages would not be obscured by the large amount of irrelevant information. Our Working Group recommended that the label explain that the listed risks were found in studies of systemic HT and their relevance to low-dose vaginal estrogen is unknown. The Group also recommended that warning text should be added in bold font to advise  patients to seek medical attention if they have vaginal bleeding or spotting while taking the medication. In addition, patients who have a history of breast cancer or other hormone-sensitive cancer should discuss the use of the medication with their oncologist.   

Status update on efforts to revise label. A citizen's petition was filed in the Spring of 2016, with signatures from more than 600 clinicians and patients and representatives of medical and professional organizations endorsing a more appropriate evidence-based label for low-dose vaginal estrogen. The FDA is continuing to review and deliberate on these issues but has not yet made a final decision.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Since publication of initial findings of the Women’s Health Initiative (WHI) in 2002, use of systemic menopausal hormone therapy (HT) has declined by some 80% among US women.¹ Against this backdrop, this year’s Menopause Update highlights the “hot off the press” updated position statement on menopausal HT from The North American Menopause Society (NAMS), summarized by Dr. JoAnn V. Pinkerton. Although this guidance is chock full of practical, evidence-based guidance, the take-home message that Dr. Pinkerton and I would like to leave readers of OBG Management with is that for women with bothersome menopausal symptoms aged in their 50s or within 10 years of the onset of menopause who are free of contraindications, use of systemic HT is appropriate.

Related Article:
Dr. Andrew M. Kaunitz on prescribing systemic HT to older women

Although menopausal vasomotor and related symptoms improve as women age, in untreated women, vulvovaginal atrophy (VVA, also known as genitourinary syndrome of menopause, or GSM) tends to progress, causing vaginal dryness and sexual dysfunction, among other symptoms. When symptomatic GSM represents the only indication for treatment, low-dose local vaginal estrogen, ospemifene, or dehydroepiandrosterone (DHEA; prasterone) is safe and effective. However, as with systemic HT, specific treatments for GSM are substantially underutilized.² The current package labeling for low-dose vaginal estrogen deters many appropriate candidates from using this safe, effective treatment. In this Update, Dr. JoAnn E. Manson reviews the rationale for updating this labeling as well as recent efforts to accomplish the task.

Read about updated NAMS guidelines on HT

Guidelines on HT have been updated by The North American Menopause Society

The 2017 hormone therapy position statement of The North American Menopause Society [published online ahead of print June 2017]. Menopause.

The North American Menopause Society Hormone Therapy (HT) Position Statement Advisory Panel, composed of more than 20 experts in menopausal women's HT, including clinicians, researchers, and epidemiologists, reviewed the 2012 HT Position Statement, evaluated prior and new literature and used levels of evidence to identify the quality of the evidence and strength of the recommendations and to find consensus for the guidelines. The following information comes from the NAMS 2017 Hormone Therapy Position Statement.³

What are the major findings?

HT is the most effective treatment for vasomotor symptoms (VMS) and GSM and has been shown to prevent bone loss and fracture. Risks of HT may differ for women depending on type, dose, duration, route of administration, and timing of initiation and whether or not a progestogen is needed. Treatment should be individualized using the best available evidence to maximize benefits and minimize risks, with periodic reevaluation about benefits and risks of continuing or discontinuing HT.

For women who are younger than age 60 or within 10 years of menopause and have no contraindication, the clearest benefit of HT is for the treatment of VMS and prevention of bone loss in those at elevated risk.

The clinical guidelines were presented to NAMS audience at the 2016 annual clinical meeting, where NAMS recommended "determining the most appropriate type, dose, formulation, and duration of HT."⁴

When to initiate HT and duration of use

In its now-published 2017 guidelines on HT, NAMS affirms the safety and efficacy of HT for symptomatic menopausal women or those at high risk for bone loss who are under age 60 or within 10 years of menopause. NAMS encourages practitioners to employ shared decision making with their patients to find the appropriate type, dose, formulation, and duration of HT, making individualized decisions based on evidence-based information, the unique health risks of women, and with periodic reassessment.

In the clinical guidelines presented in the 2016 NAMS annual meeting,⁴ key recommendations taken from the 2017 Hormone Therapy Position Statement³ include the following: For women who are aged younger than 60 years or within 10 years of menopause and have no contraindications, the benefit/risk ratio appears favorable for treatment of bothersome VMS and in those at elevated risk for bone loss or fracture.

For women who initiate HT more than 10 years from menopause or after age 60, this benefit/risk ratio appears less favorable because of greater absolute risks of coronary heart disease, stroke, venous thromboembolism, and dementia.

What about extended use of hormone therapy? There is no evidence to support routine discontinuation of HT after age 65. Decisions about longer durations of HT should be individualized and considered for indications such as persistent VMS or bone loss, with shared decision making, documentation, and periodic reevaluation. Longer duration is more favorable for estrogen therapy than for estrogen-progestin therapy, based on the Women's Health Initiative (WHI) randomized controlled trials.⁵

What about only vaginal symptoms? For bothersome GSM not relieved with over-the-counter therapies and without indications for use of systemic HT, low-dose vaginal estrogen therapy or other therapies are recommended and can be continued as long as indicated since there is minimal systemic absorption of estrogen, with serum levels remaining within the normal postmenopausal range.^6,7 For women with estrogen sensitive cancer, oncologists should be included in decision making, particularly for women on aromatase inhibitors.

Considerations for special populations Early menopause. For women with hypoestrogenism, primary ovarian insufficiency, or premature surgical menopause without contraindications, HT is recommended until at least the median age of menopause (52 years), as studies suggest that benefits outweigh the risks for effects on bone, heart, cognition, GSM, sexual function, and mood.⁸

Family history of breast cancer. Observational evidence suggests that use of HT does not further alter the risk for breast cancer in women with a family history of breast cancer. Family history is one risk, among others, that should be assessed when counseling women regarding HT.

Women who are BRCA-positive without breast cancer. For women who are BRCA-positive (higher genetic risk of breast cancer, primarily estrogen-receptor-negative), and have undergone surgical menopause (bilateral salpingo-oophorectomy), the benefits of estrogen to decrease health risks caused by premature loss of estrogen need to be considered on an individual basis.⁹ On the basis of limited observational studies, consider offering systemic HT until the median age of menopause (52 years) with longer use individualized.³

Related Article:
Is menopausal hormone therapy safe when your patient carries a BRCA mutation?

Survivors of endometrial and breast cancer with bothersome VMS. For women with prior estrogen-sensitive cancers, non-HTs should be considered first, particularly those agents studied through randomized controlled trials in this population and found to be effective. If systemic estrogen is considered for persistent symptoms after non-HT or complementary options have been unsuccessful, decisions should be made for compelling reasons and after detailed counseling, with shared decision making and in conjunction with their oncologist.³ 

Bothersome GSM. On the basis of limited observational data, there appears to be minimal to no demonstrated elevation in risk for recurrence of endometrial or breast cancer using low-dose vaginal estrogen,^3,10 but decisions should be made in conjunction with an oncologist.

Related Article:
Focus on treating genital atrophy symptoms
 

The importance of relaying the new guidelines to patients

It is important for clinicians to talk to women about their menopausal symptoms and their options for relief of symptoms or prevention of bone loss. Discussion should take into account age and time from menopause, include evidence-based information^11-13 about benefits and risks of different types of therapy, and employ shared decision making to choose the most appropriate therapy to maximize benefits and minimize risks for the individual woman.

Following the WHI initial release in 2002, both women and providers became fearful of HT and believed media hype and celebrities that compounded bioidentical HT was safer than FDA-approved HTs. However, compounded products lack safety and efficacy data, are not monitored or regulated by the FDA, and have unique risks associated with compounding, including concerns about sterility, impurities, and overdosing or underdosing, which could increase cancer risk.³

Read about modifying low-dose vaginal estrogen’s black box warning

Physicians continue to underwhelmingly prescribe low-dose vaginal estrogen for GSM 

Kingsberg SA, Krychman M, Graham S, Bernick B, Mirkin S. The Women's EMPOWER survey: identifying women's perceptions on vulvar and vaginal atrophy and its treatment. J Sex Med. 2017;14(3):413-424.

GSM is seriously underrecognized and undertreated.^2,8,14 It has a major impact on women's lives--a silent epidemic affecting women's quality of life, sexual health, interpersonal relationships, and even physical health in terms of increased risk of urinary tract infections and urinary symptoms. Unfortunately, patients are reluctant to mention the problem to their clinicians, and they do not clearly recognize it as a medical condition that has available treatment options. Clinicians also rarely receive adequate training in the management of this condition and how to discuss it with their patients. Given busy schedules and time constraints, addressing this topic often falls through the cracks, representing a missed opportunity for helping our patients with safe and effective treatments. In a recent study by Kingsberg and colleagues, an astoundingly low percentageof women with GSM symptoms received treatment. 

Details of the study

The study authors evaluated women's perceptions of GSM and available treatment options. US women aged 45 and older who reported GSM symptoms were surveyed. Of 1,858 women with a median age of 58 (range, 45-90), the study authors found that 50% had never used any treatment; 25% used over-the-counter medications; 18% were former users of GSM treatments; and 7% currently used prescribed GSM therapies.

When GSM was discussed, women were more likely than their clinicians to initiate the conversation. The main reason for women not mentioning their symptoms was the perception that GSM symptoms were a natural and inevitable part of aging. Hormonal products were perceived by women as having several downsides, including risk of systemic absorption, messiness of local creams, and the need to reuse an applicator. Overall, clinicians recommended vaginal estrogen therapy to only 23% and oral HTs to 18% of women.

The results of the study are consistent with results of earlier surveys of menopausal women. Although the survey included nearly 2,000 women, it has the potential for selection biases inherent to most Internet-based surveys. In addition, the respondents tended to be white and have higher socieconomic status, with limited representation from other groups.

Calls for the current boxed warning to be revised

GSM is highly prevalent among postmenopausal women; the condition has adverse effects on quality of life and sexual health.^2,8,14 Safe and effective treatments are available but are underutilized.^1,8,15,16 A current boxed warning appears on low-dose vaginal estrogen--class labeling that appears on all medications in the class of estrogen or HT, regardless of dose or route of administration. These warnings are based on findings from the WHI and other studies of systemic estrogen or estrogen plus progestin, which demonstrated a complex pattern of risks and benefits of HT (including increased risk of venous thrombosis or pulmonary embolism, stroke, and breast cancer [with estrogen plus progestin]).

These findings, however, do not appear to be relevant to low-dose vaginal estrogen, given minimal if any systemic absorption and much lower blood levels of hormones than found with systemic HT. Blood levels of estradiol with low-dose vaginal estrogen remain in the normal postmenopausal range, compared to several-fold elevations in hormone levels with systemic HT.^8,15,16 Additionally, observational studies of low-dose vaginal estrogen, as well as short-term randomized clinical trials, show no evidence of an increased risk of venous thromboembolic events, heart disease, stroke, breast cancer, or dementia--the listed possible adverse effects in the boxed warning. The current warning is based on extrapolating findings from systemic HT, which is inappropriate and not evidence-based for low-dose vaginal estrogen.¹⁵

The inappropriate boxed warning contributes to the problem of undertreatment of GSM in women by discouraging clinicians from prescribing the medication and dissuading patients from taking it even after purchase. Testimonials from many clinicians caring for these women have underscored that women will fill their prescription, but after seeing the boxed warning will often become alarmed and decide not to take the medication. Clinicians reported that patients often say at their next appointment: "No, I never took it. I got very scared when I saw the boxed warning." As a result, clinicians often have to spend a great deal of time explaining the limitations of, and lack of evidence for, the boxed warning on low-dose vaginal estrogen.

Related Article:
2016 Update on menopause
 

Recommended label revisions

A modified label, without a boxed warning, would be safer for women because the key messages would not be obscured by the large amount of irrelevant information. Our Working Group recommended that the label explain that the listed risks were found in studies of systemic HT and their relevance to low-dose vaginal estrogen is unknown. The Group also recommended that warning text should be added in bold font to advise  patients to seek medical attention if they have vaginal bleeding or spotting while taking the medication. In addition, patients who have a history of breast cancer or other hormone-sensitive cancer should discuss the use of the medication with their oncologist.   

Status update on efforts to revise label. A citizen's petition was filed in the Spring of 2016, with signatures from more than 600 clinicians and patients and representatives of medical and professional organizations endorsing a more appropriate evidence-based label for low-dose vaginal estrogen. The FDA is continuing to review and deliberate on these issues but has not yet made a final decision.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Since publication of initial findings of the Women’s Health Initiative (WHI) in 2002, use of systemic menopausal hormone therapy (HT) has declined by some 80% among US women.¹ Against this backdrop, this year’s Menopause Update highlights the “hot off the press” updated position statement on menopausal HT from The North American Menopause Society (NAMS), summarized by Dr. JoAnn V. Pinkerton. Although this guidance is chock full of practical, evidence-based guidance, the take-home message that Dr. Pinkerton and I would like to leave readers of OBG Management with is that for women with bothersome menopausal symptoms aged in their 50s or within 10 years of the onset of menopause who are free of contraindications, use of systemic HT is appropriate.

Related Article:
Dr. Andrew M. Kaunitz on prescribing systemic HT to older women

Although menopausal vasomotor and related symptoms improve as women age, in untreated women, vulvovaginal atrophy (VVA, also known as genitourinary syndrome of menopause, or GSM) tends to progress, causing vaginal dryness and sexual dysfunction, among other symptoms. When symptomatic GSM represents the only indication for treatment, low-dose local vaginal estrogen, ospemifene, or dehydroepiandrosterone (DHEA; prasterone) is safe and effective. However, as with systemic HT, specific treatments for GSM are substantially underutilized.² The current package labeling for low-dose vaginal estrogen deters many appropriate candidates from using this safe, effective treatment. In this Update, Dr. JoAnn E. Manson reviews the rationale for updating this labeling as well as recent efforts to accomplish the task.

Read about updated NAMS guidelines on HT

Guidelines on HT have been updated by The North American Menopause Society

The 2017 hormone therapy position statement of The North American Menopause Society [published online ahead of print June 2017]. Menopause.

The North American Menopause Society Hormone Therapy (HT) Position Statement Advisory Panel, composed of more than 20 experts in menopausal women's HT, including clinicians, researchers, and epidemiologists, reviewed the 2012 HT Position Statement, evaluated prior and new literature and used levels of evidence to identify the quality of the evidence and strength of the recommendations and to find consensus for the guidelines. The following information comes from the NAMS 2017 Hormone Therapy Position Statement.³

What are the major findings?

HT is the most effective treatment for vasomotor symptoms (VMS) and GSM and has been shown to prevent bone loss and fracture. Risks of HT may differ for women depending on type, dose, duration, route of administration, and timing of initiation and whether or not a progestogen is needed. Treatment should be individualized using the best available evidence to maximize benefits and minimize risks, with periodic reevaluation about benefits and risks of continuing or discontinuing HT.

For women who are younger than age 60 or within 10 years of menopause and have no contraindication, the clearest benefit of HT is for the treatment of VMS and prevention of bone loss in those at elevated risk.

The clinical guidelines were presented to NAMS audience at the 2016 annual clinical meeting, where NAMS recommended "determining the most appropriate type, dose, formulation, and duration of HT."⁴

When to initiate HT and duration of use

In its now-published 2017 guidelines on HT, NAMS affirms the safety and efficacy of HT for symptomatic menopausal women or those at high risk for bone loss who are under age 60 or within 10 years of menopause. NAMS encourages practitioners to employ shared decision making with their patients to find the appropriate type, dose, formulation, and duration of HT, making individualized decisions based on evidence-based information, the unique health risks of women, and with periodic reassessment.

In the clinical guidelines presented in the 2016 NAMS annual meeting,⁴ key recommendations taken from the 2017 Hormone Therapy Position Statement³ include the following: For women who are aged younger than 60 years or within 10 years of menopause and have no contraindications, the benefit/risk ratio appears favorable for treatment of bothersome VMS and in those at elevated risk for bone loss or fracture.

For women who initiate HT more than 10 years from menopause or after age 60, this benefit/risk ratio appears less favorable because of greater absolute risks of coronary heart disease, stroke, venous thromboembolism, and dementia.

What about extended use of hormone therapy? There is no evidence to support routine discontinuation of HT after age 65. Decisions about longer durations of HT should be individualized and considered for indications such as persistent VMS or bone loss, with shared decision making, documentation, and periodic reevaluation. Longer duration is more favorable for estrogen therapy than for estrogen-progestin therapy, based on the Women's Health Initiative (WHI) randomized controlled trials.⁵

What about only vaginal symptoms? For bothersome GSM not relieved with over-the-counter therapies and without indications for use of systemic HT, low-dose vaginal estrogen therapy or other therapies are recommended and can be continued as long as indicated since there is minimal systemic absorption of estrogen, with serum levels remaining within the normal postmenopausal range.^6,7 For women with estrogen sensitive cancer, oncologists should be included in decision making, particularly for women on aromatase inhibitors.

Considerations for special populations Early menopause. For women with hypoestrogenism, primary ovarian insufficiency, or premature surgical menopause without contraindications, HT is recommended until at least the median age of menopause (52 years), as studies suggest that benefits outweigh the risks for effects on bone, heart, cognition, GSM, sexual function, and mood.⁸

Family history of breast cancer. Observational evidence suggests that use of HT does not further alter the risk for breast cancer in women with a family history of breast cancer. Family history is one risk, among others, that should be assessed when counseling women regarding HT.

Women who are BRCA-positive without breast cancer. For women who are BRCA-positive (higher genetic risk of breast cancer, primarily estrogen-receptor-negative), and have undergone surgical menopause (bilateral salpingo-oophorectomy), the benefits of estrogen to decrease health risks caused by premature loss of estrogen need to be considered on an individual basis.⁹ On the basis of limited observational studies, consider offering systemic HT until the median age of menopause (52 years) with longer use individualized.³

Related Article:
Is menopausal hormone therapy safe when your patient carries a BRCA mutation?

Survivors of endometrial and breast cancer with bothersome VMS. For women with prior estrogen-sensitive cancers, non-HTs should be considered first, particularly those agents studied through randomized controlled trials in this population and found to be effective. If systemic estrogen is considered for persistent symptoms after non-HT or complementary options have been unsuccessful, decisions should be made for compelling reasons and after detailed counseling, with shared decision making and in conjunction with their oncologist.³ 

Bothersome GSM. On the basis of limited observational data, there appears to be minimal to no demonstrated elevation in risk for recurrence of endometrial or breast cancer using low-dose vaginal estrogen,^3,10 but decisions should be made in conjunction with an oncologist.

Related Article:
Focus on treating genital atrophy symptoms
 

The importance of relaying the new guidelines to patients

It is important for clinicians to talk to women about their menopausal symptoms and their options for relief of symptoms or prevention of bone loss. Discussion should take into account age and time from menopause, include evidence-based information^11-13 about benefits and risks of different types of therapy, and employ shared decision making to choose the most appropriate therapy to maximize benefits and minimize risks for the individual woman.

Following the WHI initial release in 2002, both women and providers became fearful of HT and believed media hype and celebrities that compounded bioidentical HT was safer than FDA-approved HTs. However, compounded products lack safety and efficacy data, are not monitored or regulated by the FDA, and have unique risks associated with compounding, including concerns about sterility, impurities, and overdosing or underdosing, which could increase cancer risk.³

Read about modifying low-dose vaginal estrogen’s black box warning

Physicians continue to underwhelmingly prescribe low-dose vaginal estrogen for GSM 

Kingsberg SA, Krychman M, Graham S, Bernick B, Mirkin S. The Women's EMPOWER survey: identifying women's perceptions on vulvar and vaginal atrophy and its treatment. J Sex Med. 2017;14(3):413-424.

GSM is seriously underrecognized and undertreated.^2,8,14 It has a major impact on women's lives--a silent epidemic affecting women's quality of life, sexual health, interpersonal relationships, and even physical health in terms of increased risk of urinary tract infections and urinary symptoms. Unfortunately, patients are reluctant to mention the problem to their clinicians, and they do not clearly recognize it as a medical condition that has available treatment options. Clinicians also rarely receive adequate training in the management of this condition and how to discuss it with their patients. Given busy schedules and time constraints, addressing this topic often falls through the cracks, representing a missed opportunity for helping our patients with safe and effective treatments. In a recent study by Kingsberg and colleagues, an astoundingly low percentageof women with GSM symptoms received treatment. 

Details of the study

The study authors evaluated women's perceptions of GSM and available treatment options. US women aged 45 and older who reported GSM symptoms were surveyed. Of 1,858 women with a median age of 58 (range, 45-90), the study authors found that 50% had never used any treatment; 25% used over-the-counter medications; 18% were former users of GSM treatments; and 7% currently used prescribed GSM therapies.

When GSM was discussed, women were more likely than their clinicians to initiate the conversation. The main reason for women not mentioning their symptoms was the perception that GSM symptoms were a natural and inevitable part of aging. Hormonal products were perceived by women as having several downsides, including risk of systemic absorption, messiness of local creams, and the need to reuse an applicator. Overall, clinicians recommended vaginal estrogen therapy to only 23% and oral HTs to 18% of women.

The results of the study are consistent with results of earlier surveys of menopausal women. Although the survey included nearly 2,000 women, it has the potential for selection biases inherent to most Internet-based surveys. In addition, the respondents tended to be white and have higher socieconomic status, with limited representation from other groups.

Calls for the current boxed warning to be revised

GSM is highly prevalent among postmenopausal women; the condition has adverse effects on quality of life and sexual health.^2,8,14 Safe and effective treatments are available but are underutilized.^1,8,15,16 A current boxed warning appears on low-dose vaginal estrogen--class labeling that appears on all medications in the class of estrogen or HT, regardless of dose or route of administration. These warnings are based on findings from the WHI and other studies of systemic estrogen or estrogen plus progestin, which demonstrated a complex pattern of risks and benefits of HT (including increased risk of venous thrombosis or pulmonary embolism, stroke, and breast cancer [with estrogen plus progestin]).

These findings, however, do not appear to be relevant to low-dose vaginal estrogen, given minimal if any systemic absorption and much lower blood levels of hormones than found with systemic HT. Blood levels of estradiol with low-dose vaginal estrogen remain in the normal postmenopausal range, compared to several-fold elevations in hormone levels with systemic HT.^8,15,16 Additionally, observational studies of low-dose vaginal estrogen, as well as short-term randomized clinical trials, show no evidence of an increased risk of venous thromboembolic events, heart disease, stroke, breast cancer, or dementia--the listed possible adverse effects in the boxed warning. The current warning is based on extrapolating findings from systemic HT, which is inappropriate and not evidence-based for low-dose vaginal estrogen.¹⁵

The inappropriate boxed warning contributes to the problem of undertreatment of GSM in women by discouraging clinicians from prescribing the medication and dissuading patients from taking it even after purchase. Testimonials from many clinicians caring for these women have underscored that women will fill their prescription, but after seeing the boxed warning will often become alarmed and decide not to take the medication. Clinicians reported that patients often say at their next appointment: "No, I never took it. I got very scared when I saw the boxed warning." As a result, clinicians often have to spend a great deal of time explaining the limitations of, and lack of evidence for, the boxed warning on low-dose vaginal estrogen.

Related Article:
2016 Update on menopause
 

Recommended label revisions

A modified label, without a boxed warning, would be safer for women because the key messages would not be obscured by the large amount of irrelevant information. Our Working Group recommended that the label explain that the listed risks were found in studies of systemic HT and their relevance to low-dose vaginal estrogen is unknown. The Group also recommended that warning text should be added in bold font to advise  patients to seek medical attention if they have vaginal bleeding or spotting while taking the medication. In addition, patients who have a history of breast cancer or other hormone-sensitive cancer should discuss the use of the medication with their oncologist.   

Status update on efforts to revise label. A citizen's petition was filed in the Spring of 2016, with signatures from more than 600 clinicians and patients and representatives of medical and professional organizations endorsing a more appropriate evidence-based label for low-dose vaginal estrogen. The FDA is continuing to review and deliberate on these issues but has not yet made a final decision.  

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Managing diabetes is a complex undertaking, with an extensive regimen of self-care—including regular exercise, meal planning, blood glucose monitoring, medication scheduling, and multiple visits—that is critically linked to glycemic control and the prevention of complications. Incorporating all of these elements into daily life can be daunting.^1-3

In fact, nearly half of US adults with diabetes fail to meet the recommended targets.⁴ This leads to frustration, which often manifests in psychosocial problems that further hamper efforts to manage the ­disease.^5-10 The most notable is a psychosocial disorder known as diabetes distress, which affects close to 45% of persons with diabetes.^11,12

It is important to note that diabetes distress is not a psychiatric disorder; rather, it is a broad affective reaction to the stress of living with this chronic and complex disease.^13-15 By negatively affecting adherence to a self-care regimen, diabetes distress contributes to worsening glycemic control and increasing morbidity.^16-18

Recognizing that about 80% of those with diabetes are treated in primary care settings, this review is intended to call your attention to diabetes distress, alert you to brief screening tools that can easily be incorporated into clinic visits, and offer guidance in matching proposed interventions to the aspects of diabetes self-management that cause patients the greatest distress.¹⁹

DIABETES DISTRESS: WHAT IT IS, WHAT IT'S NOT

For patients with type 2 diabetes, diabetes distress centers around four main issues

• Frustration with the demands of self-care
• Apprehension about the future and the possibility of developing serious complications
• Concern about both the quality and the cost of required medical care
• Perceived lack of support from family and/or friends.^11,12,20

As mentioned earlier, diabetes distress is not a psychiatric condition and should not be confused with major depressive disorder (MDD). Here’s help in telling the difference.

For starters, a diagnosis of depression is symptom-based.¹³ MDD requires the presence of at least five of the nine symptoms defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth ed. (DSM-5)—eg, persistent feelings of worthlessness or guilt, sleep disturbances, lack of interest in normal activities—for at least two weeks.²¹ What’s more, the diagnostic criteria for MDD do not specify a cause or disease process. Nor do they distinguish between a pathological response and an expected reaction to a stressful life event.²² Further, depression measures reflect symptoms (eg, hyperglycemia), as well as stressful experiences resulting from diabetes self-care, which may contribute to the high rate of false positives or incorrect diagnoses of MDD and missed diagnoses of diabetes distress.²³

Unlike MDD, diabetes distress has a specific cause—diabetes—and can best be understood as an emotional response to a demanding health condition.¹³ And, because the source of the problem is identified, diabetes distress can be treated with specific interventions targeting the areas causing the highest levels of stress.

When a psychiatric condition and diabetes distress overlap

MDD, anxiety disorders, and diabetes distress are all common in patients with diabetes, and the co-occurrence of a psychiatric disorder and diabetes distress is high.^24,25Thus, it is important not only to identify cases of diabetes distress but also to consider comorbid depression and/or anxiety in patients with diabetes distress.

More often, though, it is the other way around, according to the Distress and Depression in Diabetes (3D) study. The researchers recently found that 84% of patients with moderate or high diabetes distress did not fulfill the criteria for MDD, but that 67% of diabetes patients with MDD also had moderate or high diabetes distress.^13,15,17,25

The data highlight the importance of screening patients with a dual diagnosis of diabetes and MDD for diabetes distress. Keep in mind that persons diagnosed with diabetes distress and a comorbid psychiatric condition may require more complex and intensive treatment than those with either diabetes distress or MDD alone.²⁵

SCREENING FOR DIABETES DISTRESS

Diabetes distress can be easily assessed using one of several patient-reported outcome measures. Six validated measures, ranging in length from one to 28 questions, are designed for use in primary care (see Table).^26-30 Some of the measures are easily accessible online; others require a subscription to MEDLINE.

Problem Areas in Diabetes (PAID). There are three versions of PAID—a 20-item screen assessing a broad range of feelings related to living with diabetes and its treatment, a five-item version (PAID-5) with high rates of sensitivity (95%) and specificity (89%), and a single-item test (PAID-1) that is highly correlated with the longer version.^26,27

Diabetes Distress Scale (DDS). This tool is available in a 17-item measure assessing diabetes distress as it relates to the emotional burden, physician-related distress, regimen-related distress, and interpersonal distress.²⁸ DDS is also available in a short form (DDS-2) with two items and a 28-item scale specifically for patients with type 1 diabetes.^29,30 T1-DDS, the only diabetes distress measure focused on this particular patient population, assesses the seven sources of distress found to be common among adults with type 1 diabetes: powerlessness, negative social perceptions, physician distress, friend/family distress, hypoglycemia distress, management distress, and eating distress.

Studies have shown that not only do those with type 1 diabetes experience different stressors compared with their type 2 counterparts, but also that they tend to experience distress differently. For patients with type 1 diabetes, for example, powerlessness ranked as the highest source of distress, followed by eating distress and hypoglycemia distress. These sources of distress differ from the regimen distress, emotional burden, interpersonal distress, and physician distress identified by those with type 2 diabetes.³⁰

HOW TO RESPOND TO DIABETES DISTRESS

Diabetes distress is easier to identify than to successfully treat. Few validated treatments for diabetes distress exist and, to our knowledge, only two studies have assessed interventions aimed at reduction of such distress.^31,32

The REDEEM trial recruited adults with type 2 diabetes and diabetes distress to participate in a 12-month randomized controlled trial (RCT).³¹ The trial had three arms, comparing the effectiveness of a computer-assisted self-management (CASM) program alone, a CASM program plus in-person diabetes distress­–specific problem-solving therapy, and a computer-assisted minimally supportive intervention. The main outcomes included diabetes distress (using the DDS scale and subscales), self-management behaviors, and A1C.

Participants in all three arms showed significant reductions in total diabetes distress and improvements in self-management behaviors, with no significant differences among the groups. No differences in A1C were found. However, those in the CASM program plus distress-specific therapy arm showed a larger reduction in regimen distress compared with the other two groups.³¹

The DIAMOS trial recruited adults who had type 1 or type 2 diabetes, diabetes distress, and subclinical depressive symptoms for a two-arm RCT.³² One group underwent cognitive behavioral interventions, while the controls had standard group-based diabetes education. The main outcomes included diabetes distress (measured via the PAID scale), depressive symptoms, well-being, diabetes self-care, diabetes acceptance, satisfaction with diabetes treatment, A1C, and subclinical inflammation.

The intervention group showed greater improvement in diabetes distress and depressive symptoms compared with the control group, but no differences in well-being, self-care, treatment satisfaction, A1C, or subclinical inflammation were observed.³²

Both studies support the use of problem-solving therapy and cognitive behavioral interventions for patients with diabetes distress. Future research should evaluate the effectiveness of these interventions in the primary care setting.

What else to offer when challenges mount?

Diabetes is a progressive disease, and most patients experience multiple challenges over time. These typically include complications and comorbidities, physical limitations, polypharmacy, hypoglycemia, and cognitive impairment, as well as changes in everything from medication and lifestyle to insurance coverage and social support.^33,34 All increase the risk for diabetes distress, as well as related psychiatric conditions.

Aging and diabetes are independent risk factors for cognitive impairment, for example, and the presence of both increases this risk.³⁵ What’s more, diabetes alone is associated with poorer executive function, the higher-level cognitive processes that allow individuals to engage in independent, purposeful, and flexible goal-related behaviors.^36-38 Both poor cognitive function and impaired executive function interfere with the ability to perform self-care behaviors such as adjusting insulin doses, drawing insulin into a syringe, or dialing an insulin dose with an insulin pen.³⁹ This in turn can lead to frustration and increase the likelihood of moderate to high diabetes distress.

Assessing diabetes distress in patients with cognitive impairment, poor executive functioning, or other psychological limitations is particularly difficult, however, as no diabetes distress measures take such deficits into account. Thus, primary care providers without expertise in neuropsychology should consider referring patients with such problems to specialists for assessment.

The progressive nature of diabetes also highlights the need for primary care providers to periodically screen for diabetes distress and engage in ongoing discussions about what type of care is best for individual patients, and why. When developing or updating treatment plans and making recommendations, it is crucial to consider the impact the treatment would likely have on the patient’s physical and mental health and to explicitly inquire about and acknowledge his or her values and preferences for care.^40-44

It is also important to remain aware of socioeconomic changes—in employment, insurance coverage, and living situations, for example—which are not addressed in the screening tools.

Moderate to high diabetes distress scores, as well as individual items patients identify as “very serious” problems, represent clinical red flags that should be the focus of careful discussion during a medical visit. Patients with moderate to high distress should be referred to a therapist trained in cognitive behavioral therapy or problem-solving therapy. Clinicians who lack access to such resources can incorporate cognitive behavioral and problem-solving techniques into patient discussions. (See “Directing Help Where It’s Most Needed.”) All patients should be referred to a certified diabetes educator—a key component of diabetes care.^45,46

Managing diabetes is a complex undertaking, with an extensive regimen of self-care—including regular exercise, meal planning, blood glucose monitoring, medication scheduling, and multiple visits—that is critically linked to glycemic control and the prevention of complications. Incorporating all of these elements into daily life can be daunting.^1-3

In fact, nearly half of US adults with diabetes fail to meet the recommended targets.⁴ This leads to frustration, which often manifests in psychosocial problems that further hamper efforts to manage the ­disease.^5-10 The most notable is a psychosocial disorder known as diabetes distress, which affects close to 45% of persons with diabetes.^11,12

It is important to note that diabetes distress is not a psychiatric disorder; rather, it is a broad affective reaction to the stress of living with this chronic and complex disease.^13-15 By negatively affecting adherence to a self-care regimen, diabetes distress contributes to worsening glycemic control and increasing morbidity.^16-18