Leukemia, Myelodysplasia, Transplantation

Chronic myeloid leukemia (CML) is a rare myeloproliferative neoplasm that is characterized by the presence of the Philadelphia (Ph) chromosome and uninhibited expansion of bone marrow stem cells. The Ph chromosome arises from a reciprocal translocation between the Abelson (ABL) region on chromosome 9 and the breakpoint cluster region (BCR) of chromosome 22 (t(9;22)(q34;q11.2), resulting in the BCR-ABL1 fusion gene.¹BCR-ABL1 encodes an oncoprotein with constitutive tyrosine kinase activity that promotes growth and replication through downstream pathways, which is the driving factor in the pathogenesis of CML.¹

Typical treatment for CML involves life-long use of oral BCR-ABL tyrosine kinase inhibitors (TKI). Currently, 5 TKIs have regulatory approval for treatment of this disease. With the introduction of imatinib in 2001 and the subsequent development of second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs, CML has become a chronic disease with a life-expectancy that is similar to that of the general population. This article reviews the diagnosis of CML and the parameters used for monitoring response to TKI therapy; the selection of initial TKI therapy is reviewed in a separate follow-up article.

Epidemiology

According to SEER data estimates, 8430 new cases of CML were diagnosed in the United States in 2018. CML is a disease of older adults, with a median age of 65 years at diagnosis, and there is a slight male predominance. Between 2011 and 2015, the number of new CML cases was 1.8 per 100,000 persons. The median overall survival (OS) in patients with newly diagnosed chronic-phase CML (CP-CML) has not been reached.² Given the effective treatments available for managing CML, it is estimated that the prevalence of CML in the United States will plateau at 180,000 patients by 2050.³

Diagnosis

Case Presentation

A 53-year-old woman presents to her primary care physician with complaints of fatigue, early satiety, left upper quadrant abdominal pain, and an 8-lb unintentional weight loss over the prior month. Her past medical history is significant for uncontrolled diabetes, coronary artery disease requiring placement of 3 cardiac stents 2 years prior, and chronic obstructive pulmonary disease (COPD) related to a 30-pack-year history of smoking. On physicial exam her spleen is palpated 8 cm below the left costal margin. A complete blood count (CBC) with differential identifies a total white blood cell (WBC) count of 124,000/μL, with a left-shifted differential including 6% basophils, 3% eosinophils, and 3% blasts; hemoglobin is 12.4 g/dL and platelet count is 801 × 10³/µL.

• How is the diagnosis of CML made?

Clinical Features

The diagnosis of CML is often suspected based on an incidental finding of leukocytosis and, in some cases, thrombocytosis. In many cases, this is an incidental finding on routine blood work, but approximately 50% of patients will present with constitutional symptoms associated with the disease. Characteristic features of the WBC differential include left-shifted maturation with neutrophilia and immature circulating myeloid cells. Basophilia and eosinophilia are often present as well. Splenomegaly is a common sign, present in 50% to 90% of patients at diagnosis. In those patients with symptoms related to CML at diagnosis, the most common presentation includes increasing fatigue, fevers, night sweats, early satiety, and weight loss. The diagnosis is confirmed by cytogenetic studies showing the Ph chromosome abnormality, t(9; 22)(q3.4;q1.1), and/or reverse transcriptase polymerase chain reaction (PCR) showing BCR-ABL1 transcripts.

• What further testing is needed when evaluating a patient for CML?

There are 3 distinct phases of CML: chronic phase (CP), accelerated phase (AP), and blast phase (BP). Bone marrow biopsy and aspiration at diagnosis are mandatory in order to determine the phase of the disease at diagnosis. This distinction is based on the percentage of blasts, promyelocytes, and basophils present as well as the platelet count and presence or absence of extramedullary disease.⁴ The vast majority of patients at diagnosis have CML that is in the chronic phase. The typical appearance in CP-CML is a hypercellular marrow with granulocytic and occasionally megakaryocytic hyperplasia. In many cases, basophilia and/or eosinophilia are noted as well. Dysplasia is not a typical finding in CML.⁵ Bone marrow fibrosis can be seen in up to one-third of patients at diagnosis, and may indicate a slightly worse prognosis.⁶ Although a diagnosis of CML can be made without a bone marrow biopsy, complete staging and prognostication are only possible with information gained from this test, including baseline karyotype and confirmation of CP versus a more advanced phase of CML.

The criteria for diagnosing AP-CML has not been agreed upon by various groups, but the modified MD Anderson Cancer Center (MDACC) criteria are used in the majority of clinical trials evaluating the efficacy of TKIs in preventing progression to advanced phases of CML. MDACC criteria define AP-CML as the presence of one of the following: 15% to 29% blasts in the peripheral blood or bone marrow, ≥ 30% peripheral blasts plus promyelocytes, ≥ 20% basophils in the blood or bone marrow, platelet count ≤ 100 × 10³/μL unrelated to therapy, and clonal cytogenetic evolution in Ph-positive metaphases (Table).⁷

BP-CML is typically defined using the criteria developed by the International Bone Marrow Transplant Registry (IBMTR): ≥ 30% blasts in the peripheral blood and/or the bone marrow or the presence of extramedullary disease.⁸ Although not typically used in clinical trials, the revised World Health Organization (WHO) criteria for BP-CML include ≥ 20% blasts in the peripheral blood or bone marrow, extramedullary blast proliferation, and large foci or clusters of blasts in the bone marrow biopsy (Table).⁹ The defining feature of CML is the presence of the Ph chromosome abnormality. In a small subset of patients, additional chromosomal abnormalities (ACA) in the Ph-positive cells may be identified at diagnosis. Some reports indicate that the presence of “major route” ACA (trisomy 8, isochromosome 17q, a second Ph chromosome, or trisomy 19) at diagnosis may negatively impact prognosis, but other reports contradict these findings.^10,11

The typical BCR breakpoint in CML is the major breakpoint cluster region (M-BCR), which results in a 210-kDa protein (p210). Alternate breakpoints that are less frequently identified are the minor BCR (mBCR or p190), which is more commonly found in Ph-positive acute lymphoblastic leukemia (ALL), and the micro BCR (µBCR or p230), which is much less common and is often characterized by chronic neutrophilia.¹² Identifying which BCR-ABL1 transcript is present in each patient using qualitative PCR is crucial in order to ensure proper monitoring during treatment.

The most sensitive method for detecting BCR-ABL1 mRNA transcripts is the quantitative real-time PCR (RQ-PCR) assay, which is typically done on peripheral blood. RQ-PCR is capable of detecting a single CML cell in the presence of ≥ 100,000 normal cells. This test should be done during the initial diagnostic workup in order to confirm the presence of BCR-ABL1 transcripts, and it is used as a standard method for monitoring response to TKI therapy.¹³ The International Scale (IS) is a standardized approach to reporting RQ-PCR results that was developed to allow comparison of results across various laboratories and has become the gold standard for reporting BCR-ABL1 transcript values.¹⁴

Determining Risk Scores

Calculating a patient’s Sokal score or EURO risk score at diagnosis remains an important component of the diagnostic workup in CP-CML, as this information has prognostic and therapeutic implications (an online calculator is available through European LeukemiaNet [ELN]). The risk for disease progression to the accelerated or blast phases is higher in patients with intermediate- or high-risk scores compared to those with a low-risk score at diagnosis. The risk of progression in intermediate- or high-risk patients is lower when a second-generation TKI (dasatinib, nilotinib, or bosutinib) is used as frontline therapy compared to imatinib, and therefore, the National Comprehensive Cancer Network (NCCN) CML Panel recommends starting with a second-generation TKI in these patients.^15-19

Case Continued

Fluorescent in-situ hybridization using a peripheral blood sample to detect the BCR-ABL gene rearrangement is performed and is positive in 87% of cells. Bone marrow biopsy and aspiration show a 95% cellular bone marrow with granulocytic hyperplasia and 1% blasts. Cytogenetics are 46,XX,t(9;22)(q34;q11.2).²⁰ RQ-PCR assay performed to measure BCR-ABL1 transcripts in the peripheral blood shows a value of 98% IS. The patient is ultimately given a diagnosis of CP-CML. Her Sokal risk score is 1.42, making her disease high risk.

• How is response to TKI therapy measured and monitored?

After confirming a diagnosis of CML and selecting the most appropriate TKI for first-line therapy, the successful management of a CML patient relies on close monitoring and follow-up to ensure patients are meeting the desired treatment milestones. Responses in CML can be assessed based on hematologic parameters, cytogenetic results, and molecular responses. A complete hematologic response (CHR) implies complete normalization of peripheral blood counts (with the exception of TKI-induced cytopenias) and resolution of any palpable splenomegaly. The majority of patients will achieve a CHR within 4 to 6 weeks after initiating CML-directed therapy.²¹

Cytogenetic Response

Cytogenetic responses are defined by the decrease in the number of Ph chromosome–positive metaphases when assessed on bone marrow cytogenetics. A partial cytogenetic response (PCyR) is defined as having 1% to 35% Ph-positive metaphases, a major cytogenetic response (MCyR) as having 0% to 35% Ph-positive metaphases, and a CCyR implies that no Ph-positive metaphases are identified on bone marrow cytogenetics. An ideal response is the achievement of PCyR after 3 months on a TKI and a CCyR after 12 months on a TKI.²²

Molecular Response

Once a patient has achieved a CCyR, monitoring their response to therapy can only be done using RQ-PCR to measure BCR-ABL1 transcripts in the peripheral blood. The NCCN and the ELN recommend monitoring RQ-PCR from the peripheral blood every 3 months in order to assess response to TKIs.^19,23 As noted, the International Scale (IS) has become the gold standard reporting system for all BCR-ABL1 transcript levels in the majority of laboratories worldwide.^14,24 Molecular responses are based on a log-reduction in BCR-ABL1 transcripts from a standardized baseline. Many molecular responses can be correlated with cytogenetic responses such that if reliable RQ-PCR testing is available, monitoring can be done using only peripheral blood RQ-PCR rather than repeat bone marrow biopsies. For example, an early molecular response (EMR) is defined as a RQ-PCR value of ≤ 10% IS, which is approximately equivalent to a PCyR.²⁵ A value of 1% IS is approximately equivalent to CCyR. A major molecular response (MMR) is a ≥ 3-log reduction in BCR-ABL1 transcripts from baseline and is a value of ≤ 0.1% IS. Deeper levels of molecular response are best described by the log-reduction in BCR-ABL1 transcripts, with a 4-log reduction denoted as MR4.0, a 4.5-log reduction as MR4.5, and so forth. Complete molecular response (CMR) is defined by the level of sensitivity of the RQ-PCR assay being used.¹⁴

The definition of relapsed disease in CML is dependent on the type of response the patient had previously achieved. Relapse could be the loss of a hematologic or cytogenetic response, but fluctuations in BCR-ABL1 transcripts on routine RQ-PCR do not necessarily indicate relapsed CML. A 1-log increase in the level of BCR-ABL1 transcripts with a concurrent loss of MMR should prompt a bone marrow biopsy in order to assess for the loss of CCyR, and thus a cytogenetic relapse; however, this loss of MMR does not define relapse in and of itself. In the setting of relapsed disease, testing should be done to look for possible ABL kinase domain mutations, and alternate therapy should be selected.¹⁹

Multiple reports have identified the prognostic relevance of achieving an EMR at 3 and 6 months after starting TKI therapy. Marin and colleagues reported that in 282 imatinib-treated patients, there was a significant improvement in 8-year OS, progression-free survival, and cumulative incidence of CCyR and CMR in patients who had BCR-ABL1 transcripts < 9.84% IS after 3 months on treatment.²⁵ This data highlights the importance of early molecular monitoring in order to ensure the best outcomes for patients with CP-CML.

The NCCN CML guidelines and ELN recommendations both agree that an ideal response after 3 months on a TKI is BCR-ABL1 transcripts < 10% IS, but treatment is not considered to be failing at this point if the patient marginally misses this milestone. After 6 months on treatment, an ideal response is considered BCR-ABL1 transcripts < 1%–10% IS. Ideally, patients will have BCR-ABL1 transcripts < 0.1%–1% IS by the time they complete 12 months of TKI therapy, suggesting that these patients have at least achieved a CCyR.^19,23 Even after patients achieve these early milestones, frequent monitoring by RQ-PCR is required to ensure that they are maintaining their response to treatment. This will help to ensure patient compliance with treatment and will also help to identify a select subset of patients who could potentially be considered for an attempt at TKI cessation (not discussed in detail here) after a minimum of 3 years on therapy.^19,26

Conclusion

Given the successful treatments available for patients with CML, it is crucial to identify patients with this disease, ensure they receive a complete, appropriate diagnostic workup including a bone marrow biopsy and aspiration with cytogenetic testing, and select the best therapy for each individual patient. Once on treatment, the importance of frequent monitoring cannot be overstated.

Chronic myeloid leukemia (CML) is a rare myeloproliferative neoplasm that is characterized by the presence of the Philadelphia (Ph) chromosome and uninhibited expansion of bone marrow stem cells. The Ph chromosome arises from a reciprocal translocation between the Abelson (ABL) region on chromosome 9 and the breakpoint cluster region (BCR) of chromosome 22 (t(9;22)(q34;q11.2), resulting in the BCR-ABL1 fusion gene.¹BCR-ABL1 encodes an oncoprotein with constitutive tyrosine kinase activity that promotes growth and replication through downstream pathways, which is the driving factor in the pathogenesis of CML.¹

Typical treatment for CML involves life-long use of oral BCR-ABL tyrosine kinase inhibitors (TKI). Currently, 5 TKIs have regulatory approval for treatment of this disease. With the introduction of imatinib in 2001 and the subsequent development of second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs, CML has become a chronic disease with a life-expectancy that is similar to that of the general population. This article reviews the diagnosis of CML and the parameters used for monitoring response to TKI therapy; the selection of initial TKI therapy is reviewed in a separate follow-up article.

Epidemiology

According to SEER data estimates, 8430 new cases of CML were diagnosed in the United States in 2018. CML is a disease of older adults, with a median age of 65 years at diagnosis, and there is a slight male predominance. Between 2011 and 2015, the number of new CML cases was 1.8 per 100,000 persons. The median overall survival (OS) in patients with newly diagnosed chronic-phase CML (CP-CML) has not been reached.² Given the effective treatments available for managing CML, it is estimated that the prevalence of CML in the United States will plateau at 180,000 patients by 2050.³

Diagnosis

Case Presentation

A 53-year-old woman presents to her primary care physician with complaints of fatigue, early satiety, left upper quadrant abdominal pain, and an 8-lb unintentional weight loss over the prior month. Her past medical history is significant for uncontrolled diabetes, coronary artery disease requiring placement of 3 cardiac stents 2 years prior, and chronic obstructive pulmonary disease (COPD) related to a 30-pack-year history of smoking. On physicial exam her spleen is palpated 8 cm below the left costal margin. A complete blood count (CBC) with differential identifies a total white blood cell (WBC) count of 124,000/μL, with a left-shifted differential including 6% basophils, 3% eosinophils, and 3% blasts; hemoglobin is 12.4 g/dL and platelet count is 801 × 10³/µL.

• How is the diagnosis of CML made?

Clinical Features

The diagnosis of CML is often suspected based on an incidental finding of leukocytosis and, in some cases, thrombocytosis. In many cases, this is an incidental finding on routine blood work, but approximately 50% of patients will present with constitutional symptoms associated with the disease. Characteristic features of the WBC differential include left-shifted maturation with neutrophilia and immature circulating myeloid cells. Basophilia and eosinophilia are often present as well. Splenomegaly is a common sign, present in 50% to 90% of patients at diagnosis. In those patients with symptoms related to CML at diagnosis, the most common presentation includes increasing fatigue, fevers, night sweats, early satiety, and weight loss. The diagnosis is confirmed by cytogenetic studies showing the Ph chromosome abnormality, t(9; 22)(q3.4;q1.1), and/or reverse transcriptase polymerase chain reaction (PCR) showing BCR-ABL1 transcripts.

• What further testing is needed when evaluating a patient for CML?

There are 3 distinct phases of CML: chronic phase (CP), accelerated phase (AP), and blast phase (BP). Bone marrow biopsy and aspiration at diagnosis are mandatory in order to determine the phase of the disease at diagnosis. This distinction is based on the percentage of blasts, promyelocytes, and basophils present as well as the platelet count and presence or absence of extramedullary disease.⁴ The vast majority of patients at diagnosis have CML that is in the chronic phase. The typical appearance in CP-CML is a hypercellular marrow with granulocytic and occasionally megakaryocytic hyperplasia. In many cases, basophilia and/or eosinophilia are noted as well. Dysplasia is not a typical finding in CML.⁵ Bone marrow fibrosis can be seen in up to one-third of patients at diagnosis, and may indicate a slightly worse prognosis.⁶ Although a diagnosis of CML can be made without a bone marrow biopsy, complete staging and prognostication are only possible with information gained from this test, including baseline karyotype and confirmation of CP versus a more advanced phase of CML.

The criteria for diagnosing AP-CML has not been agreed upon by various groups, but the modified MD Anderson Cancer Center (MDACC) criteria are used in the majority of clinical trials evaluating the efficacy of TKIs in preventing progression to advanced phases of CML. MDACC criteria define AP-CML as the presence of one of the following: 15% to 29% blasts in the peripheral blood or bone marrow, ≥ 30% peripheral blasts plus promyelocytes, ≥ 20% basophils in the blood or bone marrow, platelet count ≤ 100 × 10³/μL unrelated to therapy, and clonal cytogenetic evolution in Ph-positive metaphases (Table).⁷

BP-CML is typically defined using the criteria developed by the International Bone Marrow Transplant Registry (IBMTR): ≥ 30% blasts in the peripheral blood and/or the bone marrow or the presence of extramedullary disease.⁸ Although not typically used in clinical trials, the revised World Health Organization (WHO) criteria for BP-CML include ≥ 20% blasts in the peripheral blood or bone marrow, extramedullary blast proliferation, and large foci or clusters of blasts in the bone marrow biopsy (Table).⁹ The defining feature of CML is the presence of the Ph chromosome abnormality. In a small subset of patients, additional chromosomal abnormalities (ACA) in the Ph-positive cells may be identified at diagnosis. Some reports indicate that the presence of “major route” ACA (trisomy 8, isochromosome 17q, a second Ph chromosome, or trisomy 19) at diagnosis may negatively impact prognosis, but other reports contradict these findings.^10,11

The typical BCR breakpoint in CML is the major breakpoint cluster region (M-BCR), which results in a 210-kDa protein (p210). Alternate breakpoints that are less frequently identified are the minor BCR (mBCR or p190), which is more commonly found in Ph-positive acute lymphoblastic leukemia (ALL), and the micro BCR (µBCR or p230), which is much less common and is often characterized by chronic neutrophilia.¹² Identifying which BCR-ABL1 transcript is present in each patient using qualitative PCR is crucial in order to ensure proper monitoring during treatment.

The most sensitive method for detecting BCR-ABL1 mRNA transcripts is the quantitative real-time PCR (RQ-PCR) assay, which is typically done on peripheral blood. RQ-PCR is capable of detecting a single CML cell in the presence of ≥ 100,000 normal cells. This test should be done during the initial diagnostic workup in order to confirm the presence of BCR-ABL1 transcripts, and it is used as a standard method for monitoring response to TKI therapy.¹³ The International Scale (IS) is a standardized approach to reporting RQ-PCR results that was developed to allow comparison of results across various laboratories and has become the gold standard for reporting BCR-ABL1 transcript values.¹⁴

Determining Risk Scores

Calculating a patient’s Sokal score or EURO risk score at diagnosis remains an important component of the diagnostic workup in CP-CML, as this information has prognostic and therapeutic implications (an online calculator is available through European LeukemiaNet [ELN]). The risk for disease progression to the accelerated or blast phases is higher in patients with intermediate- or high-risk scores compared to those with a low-risk score at diagnosis. The risk of progression in intermediate- or high-risk patients is lower when a second-generation TKI (dasatinib, nilotinib, or bosutinib) is used as frontline therapy compared to imatinib, and therefore, the National Comprehensive Cancer Network (NCCN) CML Panel recommends starting with a second-generation TKI in these patients.^15-19

Case Continued

Fluorescent in-situ hybridization using a peripheral blood sample to detect the BCR-ABL gene rearrangement is performed and is positive in 87% of cells. Bone marrow biopsy and aspiration show a 95% cellular bone marrow with granulocytic hyperplasia and 1% blasts. Cytogenetics are 46,XX,t(9;22)(q34;q11.2).²⁰ RQ-PCR assay performed to measure BCR-ABL1 transcripts in the peripheral blood shows a value of 98% IS. The patient is ultimately given a diagnosis of CP-CML. Her Sokal risk score is 1.42, making her disease high risk.

• How is response to TKI therapy measured and monitored?

After confirming a diagnosis of CML and selecting the most appropriate TKI for first-line therapy, the successful management of a CML patient relies on close monitoring and follow-up to ensure patients are meeting the desired treatment milestones. Responses in CML can be assessed based on hematologic parameters, cytogenetic results, and molecular responses. A complete hematologic response (CHR) implies complete normalization of peripheral blood counts (with the exception of TKI-induced cytopenias) and resolution of any palpable splenomegaly. The majority of patients will achieve a CHR within 4 to 6 weeks after initiating CML-directed therapy.²¹

Cytogenetic Response

Cytogenetic responses are defined by the decrease in the number of Ph chromosome–positive metaphases when assessed on bone marrow cytogenetics. A partial cytogenetic response (PCyR) is defined as having 1% to 35% Ph-positive metaphases, a major cytogenetic response (MCyR) as having 0% to 35% Ph-positive metaphases, and a CCyR implies that no Ph-positive metaphases are identified on bone marrow cytogenetics. An ideal response is the achievement of PCyR after 3 months on a TKI and a CCyR after 12 months on a TKI.²²

Molecular Response

Once a patient has achieved a CCyR, monitoring their response to therapy can only be done using RQ-PCR to measure BCR-ABL1 transcripts in the peripheral blood. The NCCN and the ELN recommend monitoring RQ-PCR from the peripheral blood every 3 months in order to assess response to TKIs.^19,23 As noted, the International Scale (IS) has become the gold standard reporting system for all BCR-ABL1 transcript levels in the majority of laboratories worldwide.^14,24 Molecular responses are based on a log-reduction in BCR-ABL1 transcripts from a standardized baseline. Many molecular responses can be correlated with cytogenetic responses such that if reliable RQ-PCR testing is available, monitoring can be done using only peripheral blood RQ-PCR rather than repeat bone marrow biopsies. For example, an early molecular response (EMR) is defined as a RQ-PCR value of ≤ 10% IS, which is approximately equivalent to a PCyR.²⁵ A value of 1% IS is approximately equivalent to CCyR. A major molecular response (MMR) is a ≥ 3-log reduction in BCR-ABL1 transcripts from baseline and is a value of ≤ 0.1% IS. Deeper levels of molecular response are best described by the log-reduction in BCR-ABL1 transcripts, with a 4-log reduction denoted as MR4.0, a 4.5-log reduction as MR4.5, and so forth. Complete molecular response (CMR) is defined by the level of sensitivity of the RQ-PCR assay being used.¹⁴

The definition of relapsed disease in CML is dependent on the type of response the patient had previously achieved. Relapse could be the loss of a hematologic or cytogenetic response, but fluctuations in BCR-ABL1 transcripts on routine RQ-PCR do not necessarily indicate relapsed CML. A 1-log increase in the level of BCR-ABL1 transcripts with a concurrent loss of MMR should prompt a bone marrow biopsy in order to assess for the loss of CCyR, and thus a cytogenetic relapse; however, this loss of MMR does not define relapse in and of itself. In the setting of relapsed disease, testing should be done to look for possible ABL kinase domain mutations, and alternate therapy should be selected.¹⁹

Multiple reports have identified the prognostic relevance of achieving an EMR at 3 and 6 months after starting TKI therapy. Marin and colleagues reported that in 282 imatinib-treated patients, there was a significant improvement in 8-year OS, progression-free survival, and cumulative incidence of CCyR and CMR in patients who had BCR-ABL1 transcripts < 9.84% IS after 3 months on treatment.²⁵ This data highlights the importance of early molecular monitoring in order to ensure the best outcomes for patients with CP-CML.

The NCCN CML guidelines and ELN recommendations both agree that an ideal response after 3 months on a TKI is BCR-ABL1 transcripts < 10% IS, but treatment is not considered to be failing at this point if the patient marginally misses this milestone. After 6 months on treatment, an ideal response is considered BCR-ABL1 transcripts < 1%–10% IS. Ideally, patients will have BCR-ABL1 transcripts < 0.1%–1% IS by the time they complete 12 months of TKI therapy, suggesting that these patients have at least achieved a CCyR.^19,23 Even after patients achieve these early milestones, frequent monitoring by RQ-PCR is required to ensure that they are maintaining their response to treatment. This will help to ensure patient compliance with treatment and will also help to identify a select subset of patients who could potentially be considered for an attempt at TKI cessation (not discussed in detail here) after a minimum of 3 years on therapy.^19,26

Conclusion

Given the successful treatments available for patients with CML, it is crucial to identify patients with this disease, ensure they receive a complete, appropriate diagnostic workup including a bone marrow biopsy and aspiration with cytogenetic testing, and select the best therapy for each individual patient. Once on treatment, the importance of frequent monitoring cannot be overstated.

Chronic myeloid leukemia (CML) is a rare myeloproliferative neoplasm that is characterized by the presence of the Philadelphia (Ph) chromosome and uninhibited expansion of bone marrow stem cells. The Ph chromosome arises from a reciprocal translocation between the Abelson (ABL) region on chromosome 9 and the breakpoint cluster region (BCR) of chromosome 22 (t(9;22)(q34;q11.2), resulting in the BCR-ABL1 fusion gene.¹BCR-ABL1 encodes an oncoprotein with constitutive tyrosine kinase activity that promotes growth and replication through downstream pathways, which is the driving factor in the pathogenesis of CML.¹

Typical treatment for CML involves life-long use of oral BCR-ABL tyrosine kinase inhibitors (TKI). Currently, 5 TKIs have regulatory approval for treatment of this disease. With the introduction of imatinib in 2001 and the subsequent development of second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs, CML has become a chronic disease with a life-expectancy that is similar to that of the general population. This article reviews the diagnosis of CML and the parameters used for monitoring response to TKI therapy; the selection of initial TKI therapy is reviewed in a separate follow-up article.

Epidemiology

According to SEER data estimates, 8430 new cases of CML were diagnosed in the United States in 2018. CML is a disease of older adults, with a median age of 65 years at diagnosis, and there is a slight male predominance. Between 2011 and 2015, the number of new CML cases was 1.8 per 100,000 persons. The median overall survival (OS) in patients with newly diagnosed chronic-phase CML (CP-CML) has not been reached.² Given the effective treatments available for managing CML, it is estimated that the prevalence of CML in the United States will plateau at 180,000 patients by 2050.³

Diagnosis

Case Presentation

A 53-year-old woman presents to her primary care physician with complaints of fatigue, early satiety, left upper quadrant abdominal pain, and an 8-lb unintentional weight loss over the prior month. Her past medical history is significant for uncontrolled diabetes, coronary artery disease requiring placement of 3 cardiac stents 2 years prior, and chronic obstructive pulmonary disease (COPD) related to a 30-pack-year history of smoking. On physicial exam her spleen is palpated 8 cm below the left costal margin. A complete blood count (CBC) with differential identifies a total white blood cell (WBC) count of 124,000/μL, with a left-shifted differential including 6% basophils, 3% eosinophils, and 3% blasts; hemoglobin is 12.4 g/dL and platelet count is 801 × 10³/µL.

• How is the diagnosis of CML made?

Clinical Features

The diagnosis of CML is often suspected based on an incidental finding of leukocytosis and, in some cases, thrombocytosis. In many cases, this is an incidental finding on routine blood work, but approximately 50% of patients will present with constitutional symptoms associated with the disease. Characteristic features of the WBC differential include left-shifted maturation with neutrophilia and immature circulating myeloid cells. Basophilia and eosinophilia are often present as well. Splenomegaly is a common sign, present in 50% to 90% of patients at diagnosis. In those patients with symptoms related to CML at diagnosis, the most common presentation includes increasing fatigue, fevers, night sweats, early satiety, and weight loss. The diagnosis is confirmed by cytogenetic studies showing the Ph chromosome abnormality, t(9; 22)(q3.4;q1.1), and/or reverse transcriptase polymerase chain reaction (PCR) showing BCR-ABL1 transcripts.

• What further testing is needed when evaluating a patient for CML?

There are 3 distinct phases of CML: chronic phase (CP), accelerated phase (AP), and blast phase (BP). Bone marrow biopsy and aspiration at diagnosis are mandatory in order to determine the phase of the disease at diagnosis. This distinction is based on the percentage of blasts, promyelocytes, and basophils present as well as the platelet count and presence or absence of extramedullary disease.⁴ The vast majority of patients at diagnosis have CML that is in the chronic phase. The typical appearance in CP-CML is a hypercellular marrow with granulocytic and occasionally megakaryocytic hyperplasia. In many cases, basophilia and/or eosinophilia are noted as well. Dysplasia is not a typical finding in CML.⁵ Bone marrow fibrosis can be seen in up to one-third of patients at diagnosis, and may indicate a slightly worse prognosis.⁶ Although a diagnosis of CML can be made without a bone marrow biopsy, complete staging and prognostication are only possible with information gained from this test, including baseline karyotype and confirmation of CP versus a more advanced phase of CML.

The criteria for diagnosing AP-CML has not been agreed upon by various groups, but the modified MD Anderson Cancer Center (MDACC) criteria are used in the majority of clinical trials evaluating the efficacy of TKIs in preventing progression to advanced phases of CML. MDACC criteria define AP-CML as the presence of one of the following: 15% to 29% blasts in the peripheral blood or bone marrow, ≥ 30% peripheral blasts plus promyelocytes, ≥ 20% basophils in the blood or bone marrow, platelet count ≤ 100 × 10³/μL unrelated to therapy, and clonal cytogenetic evolution in Ph-positive metaphases (Table).⁷

BP-CML is typically defined using the criteria developed by the International Bone Marrow Transplant Registry (IBMTR): ≥ 30% blasts in the peripheral blood and/or the bone marrow or the presence of extramedullary disease.⁸ Although not typically used in clinical trials, the revised World Health Organization (WHO) criteria for BP-CML include ≥ 20% blasts in the peripheral blood or bone marrow, extramedullary blast proliferation, and large foci or clusters of blasts in the bone marrow biopsy (Table).⁹ The defining feature of CML is the presence of the Ph chromosome abnormality. In a small subset of patients, additional chromosomal abnormalities (ACA) in the Ph-positive cells may be identified at diagnosis. Some reports indicate that the presence of “major route” ACA (trisomy 8, isochromosome 17q, a second Ph chromosome, or trisomy 19) at diagnosis may negatively impact prognosis, but other reports contradict these findings.^10,11

The typical BCR breakpoint in CML is the major breakpoint cluster region (M-BCR), which results in a 210-kDa protein (p210). Alternate breakpoints that are less frequently identified are the minor BCR (mBCR or p190), which is more commonly found in Ph-positive acute lymphoblastic leukemia (ALL), and the micro BCR (µBCR or p230), which is much less common and is often characterized by chronic neutrophilia.¹² Identifying which BCR-ABL1 transcript is present in each patient using qualitative PCR is crucial in order to ensure proper monitoring during treatment.

The most sensitive method for detecting BCR-ABL1 mRNA transcripts is the quantitative real-time PCR (RQ-PCR) assay, which is typically done on peripheral blood. RQ-PCR is capable of detecting a single CML cell in the presence of ≥ 100,000 normal cells. This test should be done during the initial diagnostic workup in order to confirm the presence of BCR-ABL1 transcripts, and it is used as a standard method for monitoring response to TKI therapy.¹³ The International Scale (IS) is a standardized approach to reporting RQ-PCR results that was developed to allow comparison of results across various laboratories and has become the gold standard for reporting BCR-ABL1 transcript values.¹⁴

Determining Risk Scores

Calculating a patient’s Sokal score or EURO risk score at diagnosis remains an important component of the diagnostic workup in CP-CML, as this information has prognostic and therapeutic implications (an online calculator is available through European LeukemiaNet [ELN]). The risk for disease progression to the accelerated or blast phases is higher in patients with intermediate- or high-risk scores compared to those with a low-risk score at diagnosis. The risk of progression in intermediate- or high-risk patients is lower when a second-generation TKI (dasatinib, nilotinib, or bosutinib) is used as frontline therapy compared to imatinib, and therefore, the National Comprehensive Cancer Network (NCCN) CML Panel recommends starting with a second-generation TKI in these patients.^15-19

Case Continued

Fluorescent in-situ hybridization using a peripheral blood sample to detect the BCR-ABL gene rearrangement is performed and is positive in 87% of cells. Bone marrow biopsy and aspiration show a 95% cellular bone marrow with granulocytic hyperplasia and 1% blasts. Cytogenetics are 46,XX,t(9;22)(q34;q11.2).²⁰ RQ-PCR assay performed to measure BCR-ABL1 transcripts in the peripheral blood shows a value of 98% IS. The patient is ultimately given a diagnosis of CP-CML. Her Sokal risk score is 1.42, making her disease high risk.

• How is response to TKI therapy measured and monitored?

After confirming a diagnosis of CML and selecting the most appropriate TKI for first-line therapy, the successful management of a CML patient relies on close monitoring and follow-up to ensure patients are meeting the desired treatment milestones. Responses in CML can be assessed based on hematologic parameters, cytogenetic results, and molecular responses. A complete hematologic response (CHR) implies complete normalization of peripheral blood counts (with the exception of TKI-induced cytopenias) and resolution of any palpable splenomegaly. The majority of patients will achieve a CHR within 4 to 6 weeks after initiating CML-directed therapy.²¹

Cytogenetic Response

Cytogenetic responses are defined by the decrease in the number of Ph chromosome–positive metaphases when assessed on bone marrow cytogenetics. A partial cytogenetic response (PCyR) is defined as having 1% to 35% Ph-positive metaphases, a major cytogenetic response (MCyR) as having 0% to 35% Ph-positive metaphases, and a CCyR implies that no Ph-positive metaphases are identified on bone marrow cytogenetics. An ideal response is the achievement of PCyR after 3 months on a TKI and a CCyR after 12 months on a TKI.²²

Molecular Response

Once a patient has achieved a CCyR, monitoring their response to therapy can only be done using RQ-PCR to measure BCR-ABL1 transcripts in the peripheral blood. The NCCN and the ELN recommend monitoring RQ-PCR from the peripheral blood every 3 months in order to assess response to TKIs.^19,23 As noted, the International Scale (IS) has become the gold standard reporting system for all BCR-ABL1 transcript levels in the majority of laboratories worldwide.^14,24 Molecular responses are based on a log-reduction in BCR-ABL1 transcripts from a standardized baseline. Many molecular responses can be correlated with cytogenetic responses such that if reliable RQ-PCR testing is available, monitoring can be done using only peripheral blood RQ-PCR rather than repeat bone marrow biopsies. For example, an early molecular response (EMR) is defined as a RQ-PCR value of ≤ 10% IS, which is approximately equivalent to a PCyR.²⁵ A value of 1% IS is approximately equivalent to CCyR. A major molecular response (MMR) is a ≥ 3-log reduction in BCR-ABL1 transcripts from baseline and is a value of ≤ 0.1% IS. Deeper levels of molecular response are best described by the log-reduction in BCR-ABL1 transcripts, with a 4-log reduction denoted as MR4.0, a 4.5-log reduction as MR4.5, and so forth. Complete molecular response (CMR) is defined by the level of sensitivity of the RQ-PCR assay being used.¹⁴

The definition of relapsed disease in CML is dependent on the type of response the patient had previously achieved. Relapse could be the loss of a hematologic or cytogenetic response, but fluctuations in BCR-ABL1 transcripts on routine RQ-PCR do not necessarily indicate relapsed CML. A 1-log increase in the level of BCR-ABL1 transcripts with a concurrent loss of MMR should prompt a bone marrow biopsy in order to assess for the loss of CCyR, and thus a cytogenetic relapse; however, this loss of MMR does not define relapse in and of itself. In the setting of relapsed disease, testing should be done to look for possible ABL kinase domain mutations, and alternate therapy should be selected.¹⁹

Multiple reports have identified the prognostic relevance of achieving an EMR at 3 and 6 months after starting TKI therapy. Marin and colleagues reported that in 282 imatinib-treated patients, there was a significant improvement in 8-year OS, progression-free survival, and cumulative incidence of CCyR and CMR in patients who had BCR-ABL1 transcripts < 9.84% IS after 3 months on treatment.²⁵ This data highlights the importance of early molecular monitoring in order to ensure the best outcomes for patients with CP-CML.

The NCCN CML guidelines and ELN recommendations both agree that an ideal response after 3 months on a TKI is BCR-ABL1 transcripts < 10% IS, but treatment is not considered to be failing at this point if the patient marginally misses this milestone. After 6 months on treatment, an ideal response is considered BCR-ABL1 transcripts < 1%–10% IS. Ideally, patients will have BCR-ABL1 transcripts < 0.1%–1% IS by the time they complete 12 months of TKI therapy, suggesting that these patients have at least achieved a CCyR.^19,23 Even after patients achieve these early milestones, frequent monitoring by RQ-PCR is required to ensure that they are maintaining their response to treatment. This will help to ensure patient compliance with treatment and will also help to identify a select subset of patients who could potentially be considered for an attempt at TKI cessation (not discussed in detail here) after a minimum of 3 years on therapy.^19,26

Conclusion

Given the successful treatments available for patients with CML, it is crucial to identify patients with this disease, ensure they receive a complete, appropriate diagnostic workup including a bone marrow biopsy and aspiration with cytogenetic testing, and select the best therapy for each individual patient. Once on treatment, the importance of frequent monitoring cannot be overstated.

WASHINGTON – Unquestionably, immunotherapy is revolutionizing the care of patients with various solid tumors and hematologic malignancies.

Neil Osterweil/MDedge News

But it’s equally true that there’s no such thing as either a free lunch or a cancer therapy free of side effects, whether it’s increased risk for heart failure associated with anthracycline-based chemotherapy, or inflammatory conditions, arrhythmias, and thromboembolic events associated with immune checkpoint inhibitors, said R. Frank Cornell, MD, of Vanderbilt University Medical Center in Nashville, Tenn.

“Early awareness and intervention is critical for improved outcomes, and a multidisciplinary approach between oncology, cardiology, the clinic nurse, and other health care providers is critical in managing these patients with these complicated therapies,” he said at the American College of Cardiology’s Advancing the Cardiovascular Care of the Oncology Patient meeting.
 

Checkpoint inhibitors and the heart

Toxicities associated with immune checkpoint inhibitors such as the programmed death 1/ligand 1 (PD-1/PD-L1) inhibitors nivolumab (Opdivo) and pembrolizumab (Keytruda) and the cytotoxic T-lymphocyte antigen 4 antibody ipilimumab (Yervoy) tend to mimic autoimmune conditions, Dr. Cornell said.

Cardiovascular events associated with these agents, while uncommon, include myocarditis, pericarditis, arrhythmias, impaired ventricular function with heart failure, vasculitis, and venous thromboembolism, he said, citing an American Society of Clinical Oncology (ASCO) clinical practice guideline (J Clin Oncol 2018;36[17]:1714-68).

Dr. Cornell described the case of a 63-year-old woman with disseminated metastatic melanoma who presented to the emergency department 10 days after starting on combination therapy with ipilimumab and nivolumab. She had developed shortness of breath, pleuritic chest pain, and a mild cough for 1 or 2 days.

Her cardiac laboratory markers had been normal at baseline, but were markedly elevated on presentation, and electrocardiograms showed complete heart block and subsequent ventricular tachycardia.

The patient was started on high-dose prednisone, but she died in hospital, and an autopsy showed that the cause of death was infiltration into the myocardium of CD3-positive and CD8-positive T lymphocytes.

“So how do we manage this? This is a good opportunity, I think, for further cardiology and oncology collaboration to develop more robust guidelines for what we can do to best prevent this,” Dr. Cornell said.

Patients started on the ipilimumab/nivolumab combination should be tested weekly for cardiac troponin, creatine kinase (CK) and CK-muscle/brain (CK-MB) weekly for the first 3-4 weeks of therapy. Therapy should be stopped if troponin levels continue to rise, and the patient should be started on high-dose steroids, he said.

The role of other anti-inflammatory agents such as infliximab (Remicade and biosimilars) is unclear and needs further study, he added.

Dr. Cornell cited a 2018 letter to The Lancet by Javid J. Moslehi, MD, and colleagues from Vanderbilt describing an increase in reports of fatal myocarditis among patients treated with checkpoint inhibitors.

“We highlight the high mortality rate with severe immune checkpoint inhibitor–related myocarditis, which is more frequent with combination PD-1 and CTLA-4 blockade, but can also occur with monotherapy. Myocarditis was observed across immune checkpoint inhibitor regimens, although it remains too early to determine whether the incidence differs between use of anti-PD1 and anti-PD-L1 drugs. Furthermore, this condition occurs early on during therapy and across cancer types,” they wrote.

Most of the patients had no preexisting cardiovascular disease, and most were not taking medications for hypertension, cardiovascular disease, or diabetes.
 

CAR-T cells and cardiac disease

The primary cardiac complications associated with CAR-T cell therapy are related to the cytokine release syndrome (CRS), a condition marked by progressive elevation in inflammatory cytokines that in turn leads to marked elevations in C-reactive protein (CRP), interferon gamma, tumor necrosis factor al, and release of pro-inflammatory cytokines including interleukin (IL) 6, IL-10, IL-12, and IL-1 beta.

In rare instances, CRS can lead to disseminated intravascular coagulation (DIC), capillary leak syndrome, and a hemophagocytic lymphohistiocytosis-like (HLH) syndrome, Dr. Cornell said.

Package inserts for the two Food and Drug Administration–approved CAR-T cell products, axicabtagene ciloleucel (Yescarta) and tisagenlecleucel (Kymriah) show that each was associated in clinical trials with a high incidence of CRS.

Among patients treated with axicabtagene ciloleucel, 94% developed CRS, which was grade 3 or greater in severity in 13%. The median time to onset was 2 days, and the median duration was 7 days. Cardiovascular adverse events included grade 3 or greater tachycardia in 2%, arrhythmias in 7%, edema in 1%, dyspnea in 3%, pleural effusion in 2%, hypotension in 15%, hypertension in 6%, and thrombosis in 1%.

Among patients treated with tisagenlecleucel, 79% treated for B-cell acute lymphoblastic leukemia (B-ALL) and 74% treated for diffuse large B cell lymphoma (DLBCL) developed CRS, which was grade 3 or greater in 49% and 23% of patients, respectively. The median time to onset was 3 days, and the median duration of CRS was 8 days.

Cardiovascular adverse events of grade 3 or greater among these patients included tachycardia in 4%, fluid overload in 7%, edema in 1%, dyspnea in 12%, pulmonary edema in 4%, hypotension in 22%, and hypertension in 6%.

Risk factors for CRS include high pre-infusion tumor burden, active infections, and concurrent inflammatory processes, Dr. Cornell said.

Prevention of cardiovascular complications of CAR-T cell therapy requires management of CRS. Patients with grade 2 or greater CRS should receive the anti-IL-6 agent tocilizumab (Actemra) 8 mg/kg intravenously over 1 hour to a maximum dose of 800 mg. Tocilizumab infusions can be repeated every 8 hours as needed if the patient is not responsive to intravenous fluids or increasing supplement oxygen, but should be limited to a maximum of three doses over 24 hours, and a maximum total of four doses.

Patients with grade 3 CRS should also receive intravenous methylprednisolone 1 mg/kg twice daily or the equivalent amount of dexamethasone, with corticosteroids continued until the severity of CRS is grade 1 or less, then tapered over 3 days,

Patients with grade 4 CRS should also receive IV methylprednisolone 1,000 mg per day for 3 days, and if symptoms improve, continue management as per grade 3, Dr. Cornell said.

Dr. Cornell reported having nothing to disclose.

WASHINGTON – Unquestionably, immunotherapy is revolutionizing the care of patients with various solid tumors and hematologic malignancies.

Neil Osterweil/MDedge News

But it’s equally true that there’s no such thing as either a free lunch or a cancer therapy free of side effects, whether it’s increased risk for heart failure associated with anthracycline-based chemotherapy, or inflammatory conditions, arrhythmias, and thromboembolic events associated with immune checkpoint inhibitors, said R. Frank Cornell, MD, of Vanderbilt University Medical Center in Nashville, Tenn.

“Early awareness and intervention is critical for improved outcomes, and a multidisciplinary approach between oncology, cardiology, the clinic nurse, and other health care providers is critical in managing these patients with these complicated therapies,” he said at the American College of Cardiology’s Advancing the Cardiovascular Care of the Oncology Patient meeting.
 

Checkpoint inhibitors and the heart

Toxicities associated with immune checkpoint inhibitors such as the programmed death 1/ligand 1 (PD-1/PD-L1) inhibitors nivolumab (Opdivo) and pembrolizumab (Keytruda) and the cytotoxic T-lymphocyte antigen 4 antibody ipilimumab (Yervoy) tend to mimic autoimmune conditions, Dr. Cornell said.

Cardiovascular events associated with these agents, while uncommon, include myocarditis, pericarditis, arrhythmias, impaired ventricular function with heart failure, vasculitis, and venous thromboembolism, he said, citing an American Society of Clinical Oncology (ASCO) clinical practice guideline (J Clin Oncol 2018;36[17]:1714-68).

Dr. Cornell described the case of a 63-year-old woman with disseminated metastatic melanoma who presented to the emergency department 10 days after starting on combination therapy with ipilimumab and nivolumab. She had developed shortness of breath, pleuritic chest pain, and a mild cough for 1 or 2 days.

Her cardiac laboratory markers had been normal at baseline, but were markedly elevated on presentation, and electrocardiograms showed complete heart block and subsequent ventricular tachycardia.

The patient was started on high-dose prednisone, but she died in hospital, and an autopsy showed that the cause of death was infiltration into the myocardium of CD3-positive and CD8-positive T lymphocytes.

“So how do we manage this? This is a good opportunity, I think, for further cardiology and oncology collaboration to develop more robust guidelines for what we can do to best prevent this,” Dr. Cornell said.

Patients started on the ipilimumab/nivolumab combination should be tested weekly for cardiac troponin, creatine kinase (CK) and CK-muscle/brain (CK-MB) weekly for the first 3-4 weeks of therapy. Therapy should be stopped if troponin levels continue to rise, and the patient should be started on high-dose steroids, he said.

The role of other anti-inflammatory agents such as infliximab (Remicade and biosimilars) is unclear and needs further study, he added.

Dr. Cornell cited a 2018 letter to The Lancet by Javid J. Moslehi, MD, and colleagues from Vanderbilt describing an increase in reports of fatal myocarditis among patients treated with checkpoint inhibitors.

“We highlight the high mortality rate with severe immune checkpoint inhibitor–related myocarditis, which is more frequent with combination PD-1 and CTLA-4 blockade, but can also occur with monotherapy. Myocarditis was observed across immune checkpoint inhibitor regimens, although it remains too early to determine whether the incidence differs between use of anti-PD1 and anti-PD-L1 drugs. Furthermore, this condition occurs early on during therapy and across cancer types,” they wrote.

Most of the patients had no preexisting cardiovascular disease, and most were not taking medications for hypertension, cardiovascular disease, or diabetes.
 

CAR-T cells and cardiac disease

The primary cardiac complications associated with CAR-T cell therapy are related to the cytokine release syndrome (CRS), a condition marked by progressive elevation in inflammatory cytokines that in turn leads to marked elevations in C-reactive protein (CRP), interferon gamma, tumor necrosis factor al, and release of pro-inflammatory cytokines including interleukin (IL) 6, IL-10, IL-12, and IL-1 beta.

In rare instances, CRS can lead to disseminated intravascular coagulation (DIC), capillary leak syndrome, and a hemophagocytic lymphohistiocytosis-like (HLH) syndrome, Dr. Cornell said.

Package inserts for the two Food and Drug Administration–approved CAR-T cell products, axicabtagene ciloleucel (Yescarta) and tisagenlecleucel (Kymriah) show that each was associated in clinical trials with a high incidence of CRS.

Among patients treated with axicabtagene ciloleucel, 94% developed CRS, which was grade 3 or greater in severity in 13%. The median time to onset was 2 days, and the median duration was 7 days. Cardiovascular adverse events included grade 3 or greater tachycardia in 2%, arrhythmias in 7%, edema in 1%, dyspnea in 3%, pleural effusion in 2%, hypotension in 15%, hypertension in 6%, and thrombosis in 1%.

Among patients treated with tisagenlecleucel, 79% treated for B-cell acute lymphoblastic leukemia (B-ALL) and 74% treated for diffuse large B cell lymphoma (DLBCL) developed CRS, which was grade 3 or greater in 49% and 23% of patients, respectively. The median time to onset was 3 days, and the median duration of CRS was 8 days.

Cardiovascular adverse events of grade 3 or greater among these patients included tachycardia in 4%, fluid overload in 7%, edema in 1%, dyspnea in 12%, pulmonary edema in 4%, hypotension in 22%, and hypertension in 6%.

Risk factors for CRS include high pre-infusion tumor burden, active infections, and concurrent inflammatory processes, Dr. Cornell said.

Prevention of cardiovascular complications of CAR-T cell therapy requires management of CRS. Patients with grade 2 or greater CRS should receive the anti-IL-6 agent tocilizumab (Actemra) 8 mg/kg intravenously over 1 hour to a maximum dose of 800 mg. Tocilizumab infusions can be repeated every 8 hours as needed if the patient is not responsive to intravenous fluids or increasing supplement oxygen, but should be limited to a maximum of three doses over 24 hours, and a maximum total of four doses.

Patients with grade 3 CRS should also receive intravenous methylprednisolone 1 mg/kg twice daily or the equivalent amount of dexamethasone, with corticosteroids continued until the severity of CRS is grade 1 or less, then tapered over 3 days,

Patients with grade 4 CRS should also receive IV methylprednisolone 1,000 mg per day for 3 days, and if symptoms improve, continue management as per grade 3, Dr. Cornell said.

Dr. Cornell reported having nothing to disclose.

WASHINGTON – Unquestionably, immunotherapy is revolutionizing the care of patients with various solid tumors and hematologic malignancies.

Neil Osterweil/MDedge News

But it’s equally true that there’s no such thing as either a free lunch or a cancer therapy free of side effects, whether it’s increased risk for heart failure associated with anthracycline-based chemotherapy, or inflammatory conditions, arrhythmias, and thromboembolic events associated with immune checkpoint inhibitors, said R. Frank Cornell, MD, of Vanderbilt University Medical Center in Nashville, Tenn.

“Early awareness and intervention is critical for improved outcomes, and a multidisciplinary approach between oncology, cardiology, the clinic nurse, and other health care providers is critical in managing these patients with these complicated therapies,” he said at the American College of Cardiology’s Advancing the Cardiovascular Care of the Oncology Patient meeting.
 

Checkpoint inhibitors and the heart

Toxicities associated with immune checkpoint inhibitors such as the programmed death 1/ligand 1 (PD-1/PD-L1) inhibitors nivolumab (Opdivo) and pembrolizumab (Keytruda) and the cytotoxic T-lymphocyte antigen 4 antibody ipilimumab (Yervoy) tend to mimic autoimmune conditions, Dr. Cornell said.

Cardiovascular events associated with these agents, while uncommon, include myocarditis, pericarditis, arrhythmias, impaired ventricular function with heart failure, vasculitis, and venous thromboembolism, he said, citing an American Society of Clinical Oncology (ASCO) clinical practice guideline (J Clin Oncol 2018;36[17]:1714-68).

Dr. Cornell described the case of a 63-year-old woman with disseminated metastatic melanoma who presented to the emergency department 10 days after starting on combination therapy with ipilimumab and nivolumab. She had developed shortness of breath, pleuritic chest pain, and a mild cough for 1 or 2 days.

Her cardiac laboratory markers had been normal at baseline, but were markedly elevated on presentation, and electrocardiograms showed complete heart block and subsequent ventricular tachycardia.

The patient was started on high-dose prednisone, but she died in hospital, and an autopsy showed that the cause of death was infiltration into the myocardium of CD3-positive and CD8-positive T lymphocytes.

“So how do we manage this? This is a good opportunity, I think, for further cardiology and oncology collaboration to develop more robust guidelines for what we can do to best prevent this,” Dr. Cornell said.

Patients started on the ipilimumab/nivolumab combination should be tested weekly for cardiac troponin, creatine kinase (CK) and CK-muscle/brain (CK-MB) weekly for the first 3-4 weeks of therapy. Therapy should be stopped if troponin levels continue to rise, and the patient should be started on high-dose steroids, he said.

The role of other anti-inflammatory agents such as infliximab (Remicade and biosimilars) is unclear and needs further study, he added.

Dr. Cornell cited a 2018 letter to The Lancet by Javid J. Moslehi, MD, and colleagues from Vanderbilt describing an increase in reports of fatal myocarditis among patients treated with checkpoint inhibitors.

“We highlight the high mortality rate with severe immune checkpoint inhibitor–related myocarditis, which is more frequent with combination PD-1 and CTLA-4 blockade, but can also occur with monotherapy. Myocarditis was observed across immune checkpoint inhibitor regimens, although it remains too early to determine whether the incidence differs between use of anti-PD1 and anti-PD-L1 drugs. Furthermore, this condition occurs early on during therapy and across cancer types,” they wrote.

Most of the patients had no preexisting cardiovascular disease, and most were not taking medications for hypertension, cardiovascular disease, or diabetes.
 

CAR-T cells and cardiac disease

The primary cardiac complications associated with CAR-T cell therapy are related to the cytokine release syndrome (CRS), a condition marked by progressive elevation in inflammatory cytokines that in turn leads to marked elevations in C-reactive protein (CRP), interferon gamma, tumor necrosis factor al, and release of pro-inflammatory cytokines including interleukin (IL) 6, IL-10, IL-12, and IL-1 beta.

In rare instances, CRS can lead to disseminated intravascular coagulation (DIC), capillary leak syndrome, and a hemophagocytic lymphohistiocytosis-like (HLH) syndrome, Dr. Cornell said.

Package inserts for the two Food and Drug Administration–approved CAR-T cell products, axicabtagene ciloleucel (Yescarta) and tisagenlecleucel (Kymriah) show that each was associated in clinical trials with a high incidence of CRS.

Among patients treated with axicabtagene ciloleucel, 94% developed CRS, which was grade 3 or greater in severity in 13%. The median time to onset was 2 days, and the median duration was 7 days. Cardiovascular adverse events included grade 3 or greater tachycardia in 2%, arrhythmias in 7%, edema in 1%, dyspnea in 3%, pleural effusion in 2%, hypotension in 15%, hypertension in 6%, and thrombosis in 1%.

Among patients treated with tisagenlecleucel, 79% treated for B-cell acute lymphoblastic leukemia (B-ALL) and 74% treated for diffuse large B cell lymphoma (DLBCL) developed CRS, which was grade 3 or greater in 49% and 23% of patients, respectively. The median time to onset was 3 days, and the median duration of CRS was 8 days.

Cardiovascular adverse events of grade 3 or greater among these patients included tachycardia in 4%, fluid overload in 7%, edema in 1%, dyspnea in 12%, pulmonary edema in 4%, hypotension in 22%, and hypertension in 6%.

Risk factors for CRS include high pre-infusion tumor burden, active infections, and concurrent inflammatory processes, Dr. Cornell said.

Prevention of cardiovascular complications of CAR-T cell therapy requires management of CRS. Patients with grade 2 or greater CRS should receive the anti-IL-6 agent tocilizumab (Actemra) 8 mg/kg intravenously over 1 hour to a maximum dose of 800 mg. Tocilizumab infusions can be repeated every 8 hours as needed if the patient is not responsive to intravenous fluids or increasing supplement oxygen, but should be limited to a maximum of three doses over 24 hours, and a maximum total of four doses.

Patients with grade 3 CRS should also receive intravenous methylprednisolone 1 mg/kg twice daily or the equivalent amount of dexamethasone, with corticosteroids continued until the severity of CRS is grade 1 or less, then tapered over 3 days,

Patients with grade 4 CRS should also receive IV methylprednisolone 1,000 mg per day for 3 days, and if symptoms improve, continue management as per grade 3, Dr. Cornell said.

Dr. Cornell reported having nothing to disclose.

The Food and Drug Administration has approved ibrutinib (Imbruvica) for use in combination with obinutuzumab to treat adults with previously untreated chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

This is the tenth FDA approval for ibrutinib, a Bruton tyrosine kinase inhibitor jointly developed and commercialized by Pharmacyclics, an AbbVie company, and Janssen Biotech.

The approval is supported by the phase 3 iLLUMINATE trial (NCT02264574).

Results from this study were recently presented at the annual meeting of the American Society of Hematology (Blood. 2018;132:691) and published in the Lancet Oncology (2019 Jan;20[1]:43-56).

The iLLUMINATE trial enrolled newly diagnosed CLL patients who were randomized to receive ibrutinib plus obinutuzumab (n = 113) or chlorambucil plus obinutuzumab (n = 116).

The median follow-up was 31.3 months. The overall response rate was 88% in the ibrutinib arm and 73% in the chlorambucil arm. The complete response rate, including complete response with incomplete marrow recovery, was 19% and 8%, respectively.

The median progression-free survival was not reached in the ibrutinib arm and was 19.0 months in the chlorambucil arm (hazard ratio, 0.23; 95% confidence interval, 0.15-0.37; P less than .0001). The estimated 30-month progression-free survival was 79% and 31%, respectively.

The most common grade 3/4 adverse events in both arms were neutropenia (36% in the ibrutinib arm and 46% in the chlorambucil arm) and thrombocytopenia (19% and 10%, respectively).

There were 10 deaths caused by adverse events in the ibrutinib arm and 3 in the chlorambucil arm. One death was considered possibly related to ibrutinib (sudden death), and another was considered possibly related to chlorambucil (neuroendocrine carcinoma of the skin).

[email protected]

The Food and Drug Administration has approved ibrutinib (Imbruvica) for use in combination with obinutuzumab to treat adults with previously untreated chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

This is the tenth FDA approval for ibrutinib, a Bruton tyrosine kinase inhibitor jointly developed and commercialized by Pharmacyclics, an AbbVie company, and Janssen Biotech.

The approval is supported by the phase 3 iLLUMINATE trial (NCT02264574).

Results from this study were recently presented at the annual meeting of the American Society of Hematology (Blood. 2018;132:691) and published in the Lancet Oncology (2019 Jan;20[1]:43-56).

The iLLUMINATE trial enrolled newly diagnosed CLL patients who were randomized to receive ibrutinib plus obinutuzumab (n = 113) or chlorambucil plus obinutuzumab (n = 116).

The median follow-up was 31.3 months. The overall response rate was 88% in the ibrutinib arm and 73% in the chlorambucil arm. The complete response rate, including complete response with incomplete marrow recovery, was 19% and 8%, respectively.

The median progression-free survival was not reached in the ibrutinib arm and was 19.0 months in the chlorambucil arm (hazard ratio, 0.23; 95% confidence interval, 0.15-0.37; P less than .0001). The estimated 30-month progression-free survival was 79% and 31%, respectively.

The most common grade 3/4 adverse events in both arms were neutropenia (36% in the ibrutinib arm and 46% in the chlorambucil arm) and thrombocytopenia (19% and 10%, respectively).

There were 10 deaths caused by adverse events in the ibrutinib arm and 3 in the chlorambucil arm. One death was considered possibly related to ibrutinib (sudden death), and another was considered possibly related to chlorambucil (neuroendocrine carcinoma of the skin).

[email protected]

The Food and Drug Administration has approved ibrutinib (Imbruvica) for use in combination with obinutuzumab to treat adults with previously untreated chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

This is the tenth FDA approval for ibrutinib, a Bruton tyrosine kinase inhibitor jointly developed and commercialized by Pharmacyclics, an AbbVie company, and Janssen Biotech.

The approval is supported by the phase 3 iLLUMINATE trial (NCT02264574).

Results from this study were recently presented at the annual meeting of the American Society of Hematology (Blood. 2018;132:691) and published in the Lancet Oncology (2019 Jan;20[1]:43-56).

The iLLUMINATE trial enrolled newly diagnosed CLL patients who were randomized to receive ibrutinib plus obinutuzumab (n = 113) or chlorambucil plus obinutuzumab (n = 116).

The median follow-up was 31.3 months. The overall response rate was 88% in the ibrutinib arm and 73% in the chlorambucil arm. The complete response rate, including complete response with incomplete marrow recovery, was 19% and 8%, respectively.

The median progression-free survival was not reached in the ibrutinib arm and was 19.0 months in the chlorambucil arm (hazard ratio, 0.23; 95% confidence interval, 0.15-0.37; P less than .0001). The estimated 30-month progression-free survival was 79% and 31%, respectively.

The most common grade 3/4 adverse events in both arms were neutropenia (36% in the ibrutinib arm and 46% in the chlorambucil arm) and thrombocytopenia (19% and 10%, respectively).

There were 10 deaths caused by adverse events in the ibrutinib arm and 3 in the chlorambucil arm. One death was considered possibly related to ibrutinib (sudden death), and another was considered possibly related to chlorambucil (neuroendocrine carcinoma of the skin).

[email protected]

The European Commission (EC) has expanded the approved indication for blinatumomab (Blincyto).

The drug is now approved in Europe to treat adults with Philadelphia chromosome–negative (Ph–), CD19-positive B-cell precursor acute lymphoblastic leukemia (BCP-ALL) in first or second complete remission with minimal residual disease (MRD) of at least 0.1%.

Blinatumomab is already approved in Europe to treat adults with Ph–, CD19-positive relapsed/refractory BCP-ALL and children aged 1 year or older who have relapsed/refractory Ph–, CD19-positive BCP-ALL and have received at least two prior therapies or relapsed after allogeneic hematopoietic stem cell transplant.

The drug was approved in the United States in March 2018 for the treatment of adults and children with BCP-ALL in first or second complete remission with MRD of at least 0.1%.

The EC’s decision to approve blinatumomab in MRD-positive patients was supported by the phase 2 BLAST trial (Blood. 2018;131[14]:1522-31).

The EC’s approval is also based on a positive opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP).

That opinion, issued in November 2018, was a reversal of the opinion the committee issued in July 2018. At that time, the CHMP said the available data did not support approval for blinatumomab to treat MRD-positive BCP-ALL.

The CHMP acknowledged that blinatumomab produced MRD negativity in many patients in the BLAST trial but said there was no strong evidence that this led to improved survival. As a result, the CHMP said the benefits of blinatumomab do not outweigh its risks in MRD-positive BCP-ALL patients.

However, Amgen requested a reexamination of the CHMP’s opinion. During the reexamination, the CHMP reviewed all the data and consulted a group of experts.

The experts echoed the CHMP’s prior sentiment that there was no strong evidence of improved survival in MRD-positive patients treated with blinatumomab. However, they also said the data indicate a good response to blinatumomab, with around 78% of patients becoming negative for MRD after treatment.

Noting that MRD-positive patients have a high risk of relapse and few treatment options, the CHMP concluded that the benefits of blinatumomab outweigh its risks in this patient population.

The CHMP recommended expanding the approved indication for blinatumomab but also requested that Amgen provide data from ongoing studies of the drug in MRD-positive patients.

[email protected]

The European Commission (EC) has expanded the approved indication for blinatumomab (Blincyto).

The drug is now approved in Europe to treat adults with Philadelphia chromosome–negative (Ph–), CD19-positive B-cell precursor acute lymphoblastic leukemia (BCP-ALL) in first or second complete remission with minimal residual disease (MRD) of at least 0.1%.

Blinatumomab is already approved in Europe to treat adults with Ph–, CD19-positive relapsed/refractory BCP-ALL and children aged 1 year or older who have relapsed/refractory Ph–, CD19-positive BCP-ALL and have received at least two prior therapies or relapsed after allogeneic hematopoietic stem cell transplant.

The drug was approved in the United States in March 2018 for the treatment of adults and children with BCP-ALL in first or second complete remission with MRD of at least 0.1%.

The EC’s decision to approve blinatumomab in MRD-positive patients was supported by the phase 2 BLAST trial (Blood. 2018;131[14]:1522-31).

The EC’s approval is also based on a positive opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP).

That opinion, issued in November 2018, was a reversal of the opinion the committee issued in July 2018. At that time, the CHMP said the available data did not support approval for blinatumomab to treat MRD-positive BCP-ALL.

The CHMP acknowledged that blinatumomab produced MRD negativity in many patients in the BLAST trial but said there was no strong evidence that this led to improved survival. As a result, the CHMP said the benefits of blinatumomab do not outweigh its risks in MRD-positive BCP-ALL patients.

However, Amgen requested a reexamination of the CHMP’s opinion. During the reexamination, the CHMP reviewed all the data and consulted a group of experts.

The experts echoed the CHMP’s prior sentiment that there was no strong evidence of improved survival in MRD-positive patients treated with blinatumomab. However, they also said the data indicate a good response to blinatumomab, with around 78% of patients becoming negative for MRD after treatment.

Noting that MRD-positive patients have a high risk of relapse and few treatment options, the CHMP concluded that the benefits of blinatumomab outweigh its risks in this patient population.

The CHMP recommended expanding the approved indication for blinatumomab but also requested that Amgen provide data from ongoing studies of the drug in MRD-positive patients.

[email protected]

The European Commission (EC) has expanded the approved indication for blinatumomab (Blincyto).

The drug is now approved in Europe to treat adults with Philadelphia chromosome–negative (Ph–), CD19-positive B-cell precursor acute lymphoblastic leukemia (BCP-ALL) in first or second complete remission with minimal residual disease (MRD) of at least 0.1%.

Blinatumomab is already approved in Europe to treat adults with Ph–, CD19-positive relapsed/refractory BCP-ALL and children aged 1 year or older who have relapsed/refractory Ph–, CD19-positive BCP-ALL and have received at least two prior therapies or relapsed after allogeneic hematopoietic stem cell transplant.

The drug was approved in the United States in March 2018 for the treatment of adults and children with BCP-ALL in first or second complete remission with MRD of at least 0.1%.

The EC’s decision to approve blinatumomab in MRD-positive patients was supported by the phase 2 BLAST trial (Blood. 2018;131[14]:1522-31).

The EC’s approval is also based on a positive opinion from the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP).

That opinion, issued in November 2018, was a reversal of the opinion the committee issued in July 2018. At that time, the CHMP said the available data did not support approval for blinatumomab to treat MRD-positive BCP-ALL.

The CHMP acknowledged that blinatumomab produced MRD negativity in many patients in the BLAST trial but said there was no strong evidence that this led to improved survival. As a result, the CHMP said the benefits of blinatumomab do not outweigh its risks in MRD-positive BCP-ALL patients.

However, Amgen requested a reexamination of the CHMP’s opinion. During the reexamination, the CHMP reviewed all the data and consulted a group of experts.

The experts echoed the CHMP’s prior sentiment that there was no strong evidence of improved survival in MRD-positive patients treated with blinatumomab. However, they also said the data indicate a good response to blinatumomab, with around 78% of patients becoming negative for MRD after treatment.

Noting that MRD-positive patients have a high risk of relapse and few treatment options, the CHMP concluded that the benefits of blinatumomab outweigh its risks in this patient population.

The CHMP recommended expanding the approved indication for blinatumomab but also requested that Amgen provide data from ongoing studies of the drug in MRD-positive patients.

[email protected]

SAN DIEGO – Ibrutinib treatment continued before, during, and after infusion of the CD19-specific chimeric antigen receptor (CAR) T-cell therapy JCAR014 in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) appears to improve patient responses and decrease the risk of severe cytokine release syndrome.

The findings come from a comparison of sequential cohorts from a phase 1/2 study.

At 4 weeks after infusion, the approach was highly efficacious; overall response rates by 2008 International Workshop on CLL (IWCLL) criteria were 83% in 24 patients who received the uninterrupted ibrutinib regimen along with the JCAR014 therapy – a combination of CD4 and CD8 T cells – and 65% in 19 patients from a prior cohort who did not receive continuous ibrutinib, Jordan Gauthier, MD, reported at the annual meeting of the American Society of Hematology.

Concurrent ibrutinib was generally well tolerated, with 13 of 19 patients in the ibrutinib cohort receiving treatment as planned without discontinuation. The rates of grade 1 or higher cytokine release syndrome (CRS) were statistically similar in the ibrutinib and no-ibrutinib cohorts (74% and 92%, respectively). However, the rates of severe CRS (grade 3 or higher) were, strikingly, 0% and 25%, respectively, said Dr. Gauthier, a senior fellow in the Turtle Lab at Fred Hutchinson Cancer Center, Seattle.

Neurotoxicity occurred in 32% and 42% of patients in the groups; severe neurotoxicity occurred in 26% and 29%, respectively.

In the ibrutinib cohort, one patient with grade 2 CRS developed fatal presumed cardiac arrhythmia; in the no-ibrutinib cohort, one patient died from a CAR T cell–related toxicity.

Notably, a trend toward better expansion of CD8 CAR T cells and a significantly greater expansion of CD4 CAR T cells was observed in the ibrutinib cohort, he said.

The study was designed to assess JCAR014, and based on the initial cohort findings published in 2017, established a regimen of cyclophosphamide and fludarabine (Cy/Flu) lymphodepletion followed by JCAR014 infusion at 2 x 10⁶ CAR T cells/kg. The study was not a randomized, head-to-head comparison but the groups were similar with respect to both patient and disease characteristics, Dr. Gauthier noted.

The outcomes in the first cohort were then compared retrospectively with those from the subsequent cohort of patients who received Cy/Flu with 2 x 10⁶ CAR T cells/kg with concurrent ibrutinib administered at 420 mg per day from at least 2 weeks prior to leukapheresis until at least 3 months after JCAR014 infusion.

The rationale for uninterrupted ibrutinib in relapsed/refractory CLL patients receiving JCAR014 included potential prevention of tumor flare, mobilization of CLL cells into the blood from the lymph nodes, improvement of CAR T-cell function, and a decrease in CAR T-cell related toxicity, he said.

The concurrent administration of ibrutinib and JCAR014 was feasible for most patients. “[It] induced high response rates and deep responses early on at 4 weeks, and it was associated with higher in vivo expansion of CD4 CAR T cells and with lower rates of severe toxicity,” Dr. Gauthier said. “The next step is to hopefully validate these findings in a prospective phase 1/2 study.”

Dr. Gauthier reported having no financial disclosures.

[email protected]

SOURCE: Gauthier J et al. ASH 18, Abstract 299.

SAN DIEGO – Ibrutinib treatment continued before, during, and after infusion of the CD19-specific chimeric antigen receptor (CAR) T-cell therapy JCAR014 in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) appears to improve patient responses and decrease the risk of severe cytokine release syndrome.

The findings come from a comparison of sequential cohorts from a phase 1/2 study.

At 4 weeks after infusion, the approach was highly efficacious; overall response rates by 2008 International Workshop on CLL (IWCLL) criteria were 83% in 24 patients who received the uninterrupted ibrutinib regimen along with the JCAR014 therapy – a combination of CD4 and CD8 T cells – and 65% in 19 patients from a prior cohort who did not receive continuous ibrutinib, Jordan Gauthier, MD, reported at the annual meeting of the American Society of Hematology.

Concurrent ibrutinib was generally well tolerated, with 13 of 19 patients in the ibrutinib cohort receiving treatment as planned without discontinuation. The rates of grade 1 or higher cytokine release syndrome (CRS) were statistically similar in the ibrutinib and no-ibrutinib cohorts (74% and 92%, respectively). However, the rates of severe CRS (grade 3 or higher) were, strikingly, 0% and 25%, respectively, said Dr. Gauthier, a senior fellow in the Turtle Lab at Fred Hutchinson Cancer Center, Seattle.

Neurotoxicity occurred in 32% and 42% of patients in the groups; severe neurotoxicity occurred in 26% and 29%, respectively.

In the ibrutinib cohort, one patient with grade 2 CRS developed fatal presumed cardiac arrhythmia; in the no-ibrutinib cohort, one patient died from a CAR T cell–related toxicity.

Notably, a trend toward better expansion of CD8 CAR T cells and a significantly greater expansion of CD4 CAR T cells was observed in the ibrutinib cohort, he said.

The study was designed to assess JCAR014, and based on the initial cohort findings published in 2017, established a regimen of cyclophosphamide and fludarabine (Cy/Flu) lymphodepletion followed by JCAR014 infusion at 2 x 10⁶ CAR T cells/kg. The study was not a randomized, head-to-head comparison but the groups were similar with respect to both patient and disease characteristics, Dr. Gauthier noted.

The outcomes in the first cohort were then compared retrospectively with those from the subsequent cohort of patients who received Cy/Flu with 2 x 10⁶ CAR T cells/kg with concurrent ibrutinib administered at 420 mg per day from at least 2 weeks prior to leukapheresis until at least 3 months after JCAR014 infusion.

The rationale for uninterrupted ibrutinib in relapsed/refractory CLL patients receiving JCAR014 included potential prevention of tumor flare, mobilization of CLL cells into the blood from the lymph nodes, improvement of CAR T-cell function, and a decrease in CAR T-cell related toxicity, he said.

The concurrent administration of ibrutinib and JCAR014 was feasible for most patients. “[It] induced high response rates and deep responses early on at 4 weeks, and it was associated with higher in vivo expansion of CD4 CAR T cells and with lower rates of severe toxicity,” Dr. Gauthier said. “The next step is to hopefully validate these findings in a prospective phase 1/2 study.”

Dr. Gauthier reported having no financial disclosures.

[email protected]

SOURCE: Gauthier J et al. ASH 18, Abstract 299.

SAN DIEGO – Ibrutinib treatment continued before, during, and after infusion of the CD19-specific chimeric antigen receptor (CAR) T-cell therapy JCAR014 in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) appears to improve patient responses and decrease the risk of severe cytokine release syndrome.

The findings come from a comparison of sequential cohorts from a phase 1/2 study.

At 4 weeks after infusion, the approach was highly efficacious; overall response rates by 2008 International Workshop on CLL (IWCLL) criteria were 83% in 24 patients who received the uninterrupted ibrutinib regimen along with the JCAR014 therapy – a combination of CD4 and CD8 T cells – and 65% in 19 patients from a prior cohort who did not receive continuous ibrutinib, Jordan Gauthier, MD, reported at the annual meeting of the American Society of Hematology.

Concurrent ibrutinib was generally well tolerated, with 13 of 19 patients in the ibrutinib cohort receiving treatment as planned without discontinuation. The rates of grade 1 or higher cytokine release syndrome (CRS) were statistically similar in the ibrutinib and no-ibrutinib cohorts (74% and 92%, respectively). However, the rates of severe CRS (grade 3 or higher) were, strikingly, 0% and 25%, respectively, said Dr. Gauthier, a senior fellow in the Turtle Lab at Fred Hutchinson Cancer Center, Seattle.

Neurotoxicity occurred in 32% and 42% of patients in the groups; severe neurotoxicity occurred in 26% and 29%, respectively.

In the ibrutinib cohort, one patient with grade 2 CRS developed fatal presumed cardiac arrhythmia; in the no-ibrutinib cohort, one patient died from a CAR T cell–related toxicity.

Notably, a trend toward better expansion of CD8 CAR T cells and a significantly greater expansion of CD4 CAR T cells was observed in the ibrutinib cohort, he said.

The study was designed to assess JCAR014, and based on the initial cohort findings published in 2017, established a regimen of cyclophosphamide and fludarabine (Cy/Flu) lymphodepletion followed by JCAR014 infusion at 2 x 10⁶ CAR T cells/kg. The study was not a randomized, head-to-head comparison but the groups were similar with respect to both patient and disease characteristics, Dr. Gauthier noted.

The outcomes in the first cohort were then compared retrospectively with those from the subsequent cohort of patients who received Cy/Flu with 2 x 10⁶ CAR T cells/kg with concurrent ibrutinib administered at 420 mg per day from at least 2 weeks prior to leukapheresis until at least 3 months after JCAR014 infusion.

The rationale for uninterrupted ibrutinib in relapsed/refractory CLL patients receiving JCAR014 included potential prevention of tumor flare, mobilization of CLL cells into the blood from the lymph nodes, improvement of CAR T-cell function, and a decrease in CAR T-cell related toxicity, he said.

The concurrent administration of ibrutinib and JCAR014 was feasible for most patients. “[It] induced high response rates and deep responses early on at 4 weeks, and it was associated with higher in vivo expansion of CD4 CAR T cells and with lower rates of severe toxicity,” Dr. Gauthier said. “The next step is to hopefully validate these findings in a prospective phase 1/2 study.”

Dr. Gauthier reported having no financial disclosures.

[email protected]

SOURCE: Gauthier J et al. ASH 18, Abstract 299.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

Aplastic anemia is a rare hematologic disorder marked by pancytopenia and a hypocellular marrow. Aplastic anemia results from either inherited or acquired causes, and the treatment approach varies significantly between the 2 causes. This article reviews the treatment of inherited and acquired forms of aplastic anemia. The approach to evaluation and diagnosis of aplastic anemia is reviewed in a separate article.

Inherited Aplastic Anemia

First-line treatment options for patients with inherited marrow failure syndromes (IMFS) are androgen therapy and hematopoietic stem cell transplant (HSCT). When evaluating patients for HSCT, it is critical to identify the presence of an IMFS, as the risk and mortality associated with the conditioning regimen, stem cell source, graft-versus-host disease (GVHD), and secondary malignancies differ between patients with IMFS and those with acquired marrow failure syndromes or hematologic malignancies.

Potential sibling donors need to be screened for donor candidacy as well as for the inherited defect.¹ Among patients with Fanconi anemia or a telomere biology disorder, the stem cell source must be considered, with bone marrow demonstrating lower rates of acute GVHD than a peripheral blood stem cell source.^2-4 In IMFS patients, the donor cell type may affect the choice of conditioning regimen.^5,6 Reduced-intensity conditioning in lieu of myeloablative conditioning without total body irradiation has proved feasible in patients with Fanconi anemia, and is associated with a reduced risk of secondary malignancies.^5,6 Incorporation of fludarabine in the conditioning regimen of patients without a matched sibling donor is associated with superior engraftment and survival^2,5,7 compared to cyclophosphamide conditioning, which was historically used in matched related donors.^6,8 The addition of fludarabine appears to be especially beneficial in older patients, in whom its use is associated with lower rates of graft failure, likely due to increased immunosuppression at the time of engraftment.^7,9 Fludarabine has also been incorporated into conditioning regimens for patients with a telomere biology disorder, but outcomes data is limited.⁵

For patients presenting with acute myeloid leukemia (AML) or a high-risk myelodysplastic syndrome (MDS) who are subsequently diagnosed with an IMFS, treatment can be more complex, as these patients are at high risk for toxicity from standard chemotherapy. Limited data suggests that induction therapy and transplantation are feasible in this group of patients, and this approach is associated with increased overall survival (OS) despite lower OS rates than those of IMFS patients who present prior to the development of MDS or AML.^10,11 Further work is needed to determine the optimal induction regimen that balances the risks of treatment-related mortality and complications associated with conditioning regimens, risk of relapse, and risk of secondary malignancies, especially in the cohort of patients diagnosed at an older age.

Acquired Aplastic Anemia

Supportive Care

While the workup and treatment plan is being established, attention should be directed at supportive care for prevention of complications. The most common complications leading to death in patients with significant pancytopenia and neutropenia are opportunistic infections and hemorrhagic complications.¹²

Transfusion support is critical to avoid symptomatic anemia and hemorrhagic complications related to thrombocytopenia, which typically occur with platelet counts lower than 10,000 cells/µL. However, transfusion carries the risk of alloimmunization (which may persist for years following transfusion) and transfusion-related graft versus host disease (trGVHD), and thus use of transfusion should be minimized when possible.^13,14 Transfusion support is often required to prevent complications associated with thrombocytopenia and anemia; all blood products given to patients with aplastic anemia should be irradiated and leukoreduced to reduce the risk of both alloimmunization and trGVHD. Guidelines from the British Society for Haematology recommend routine screening for Rh and Kell antibodies to reduce the risk of alloimmunization.¹⁵ Infectious complications remain a common cause of morbidity and mortality in patients with aplastic anemia who have prolonged neutropenia (defined as an absolute neutrophil count [ANC] < 500 cells/µL).^16-19 Therefore, patients should receive broad-spectrum antibiotics with antipseudomonal coverage. In a study by Tichelli and colleagues evaluating the role of granulocyte-colony stimulating factor (G-CSF) in patients with SAA receiving immunosuppressive therapy, 55% of all patient deaths were secondary to infection.²⁰ There was no OS benefit seen in patients who received G-CSF, though a significantly lower rate of infection was observed in the G-CSF arm compared to those not receiving G-CSF (56% versus 81%, P = 0.006).This difference was largely driven by a decrease in infectious episodes in patients with very severe aplastic anemia (VSAA) treated with G-CSF as compared to those who did not receive this therapy (22% versus 48%, P = 0.014).²⁰

Angio-invasive pulmonary aspergillosis and Zygomycetes (eg, Rhizopus, Mucor species) remain major causes of mortality related to opportunistic mycotic infections in patients with aplastic anemia.¹⁸ The infectious risk is directly related to the duration and severity of neutropenia, with one study demonstrating a significant increase in risk in AML patients with neutropenia lasting longer than 3 weeks.²¹ Invasive fungal infections carry a high mortality in patients with severe neutropenia, though due to earlier recognition and empiric antifungal therapy with extended-spectrum azoles, overall mortality secondary to invasive fungal infections is declining.^19,22

While neutropenia related to cytotoxic chemotherapy is commonly associated with gram-negative bacteria due to disruption of mucosal barriers, patients with aplastic anemia have an increased incidence of gram-positive bacteremia with staphylococcal species compared to other neutropenic populations.^18,19 This appears to be changing with time. Valdez and colleagues demonstrated a decrease in prevalence of coagulase-negative staphylococcal infections, increased prevalence of gram-positive bacilli bacteremia, and no change in prevalence of gram-negative bacteremia in patients with aplastic anemia treated between 1989 and 2008.²² Gram-negative bacteremia caused by Stenotrophomonas maltophila, Escherichia coli, Klebsiella pneumoniae, Citrobacter, and Proteus has also been reported.¹⁹ Despite a lack of clinical trials investigating the role of antifungal and antibacterial prophylaxis for patients with aplastic anemia, most centers initiate antifungal prophylaxis in patients with severe aplastic anema (SAA) or VSAA with an anti-mold agent such as voriconazole or posaconazole (which has the additional benefit compared to voriconazole of covering Mucor species).^17,23 This is especially true for patients who have received ATG or undergone HSCT. For antimicrobial prophylaxis, a fluoroquinolone antibiotic with a spectrum of activity against Pseudomonas should be considered for patients with an ANC < 500 cells/µL.¹⁷ Acyclovir or valacyclovir prophylaxis is recommended for varicella-zoster virus and herpes simplex virus. Cytomegalovirus reactivation is minimal in patients with aplastic anemia, unless multiple courses of ATG are used.

Iron overload is another complication the provider must be aware of in the setting of increased transfusions in aplastic anemia patients. Lee and colleagues demonstrated that iron chelation therapy using deferasirox is effective at reducing serum ferritin levels in patients with aplastic anemia (median ferritin level: 3254 ng/mL prior to therapy, 1854 ng/mL following), and is associated with no serious adverse events (most common adverse events included nausea, diarrhea, vomiting, and rash).²⁴ Approximately 25% of patients in this trial demonstrated an increase in creatinine, with patients taking concomitant cyclosporine more affected than those on chelation therapy alone.²⁴ For patients following HSCT or with improved hematopoiesis following immunosuppressive therapy, phlebotomy can be used to treat iron overload in lieu of chelation therapy.¹⁵

Approach to Therapy

The main treatment options for SAA and VSAA include allogeneic bone marrow transplant and immunosuppression. The deciding factors as to which treatment is best initially depends on the availability of HLA-matched related donors and age (Figure 1 and Figure 2). Survival is decreased in patients with SAA or VSAA who delay initiation of therapy, and therefore prompt referral for HLA typing and evaluation for bone marrow transplant is a very important first step in managing aplastic anemia.

Matched Sibling Donor Transplant

Current standards of care recommend HLA-matched sibling donor transplant for patients with SAA or VSAA who are younger than 50 years of age, with the caveat that integration of fludarabine and reduced cyclophosphamide dosing along with ATG shows the best overall outcomes. Locasciulli and colleagues examined outcomes in patients given either immunosuppressive therapy or sibling HSCT between 1991-1996 and 1997-2002, respectively, and found that sibling HSCT was associated with a superior 10-year OS compared to immunosuppressive therapy (73% versus 68%).²⁵ Interestingly in this study, there was no OS improvement seen with immunosuppressive therapy alone (69% versus 73%) between the 2 time periods, despite increased OS in both sibling HSCT (74% and 80%) and matched unrelated donor HSCT (38% and 65%).²⁵ Though total body irradiation has been used in the past, it is typically not included in current conditioning regimens for matched related donor transplants.²⁶

Current conditioning regimens typically use a combination of cyclophosphamide and ATG^27,28 with or without fludarabine. Fludarabine-based conditioning regimens have shown promise in patients undergoing sibling HSCT. Maury and colleagues evaluated the role of fludarabine in addition to low-dose cyclophosphamide and ATG compared to cyclophosphamide alone or in combination with ATG in patients over age 30 undergoing sibling HSCT.⁹ There was a nonsignificant improvement in 5-year OS in the fludarabine arm compared to controls (77% ± 8% versus 60% ± 3%, P = 0.14) in the pooled analysis, but when adjusted for age the fludarabine arm had a significantly lower relative risk (RR) of death (RR, 0.44; P = 0.04) compared to the control arm. Shin et al reported outcomes with fludarabine/cyclophosphamide/ATG, with excellent overall outcomes and no difference in patients older or younger than 40 years.²⁹ In addition, Kim et al evaluated their experience with patients older than 40 years of age receiving matched related donors, finding comparable outcomes in those aged 41 to 50 years compared to younger patients. Outcomes did decline in those over the age of 50 years.³⁰ Long-term data for matched related donor transplant for aplastic anemia shows excellent long-term outcomes, with minimal chronic GVHD and good performance status.³¹ Hence, these factors support the role of matched related donor transplant as the initial treatment in SAA and VSAA.

Regarding the role of transplant for patients who lack a matched related donor, a growing body of literature demonstrating identical outcomes between matched related and matched unrelated donor (MUD) transplants for pediatric patients^32,33 supports recent recommendations for upfront unrelated donor transplantation for aplastic anemia.^34,35

Immunosuppressive Therapy

For patients without an HLA-matched sibling donor or those who are older than 50 years of age, immunosuppressive therapy is the first-line therapy. ATG and cyclosporine A are the treatments of choice.³⁶ The potential effectiveness of immunosuppressive therapy in treating aplastic anemia was initially observed in patients in whom autologous transplant failed but who still experienced hematopoietic reconstitution despite the failed graft; this observation led to the hypothesis that the conditioning regimen may have an effect on hematopoiesis.^16,36,37

Anti-thymocyte globulin. Immunosuppressive therapy with ATG has been used for the treatment of aplastic anemia since the 1980s.³⁸ Historically, rabbit ATG had been used, but a 2011 study of horse ATG demonstrated superior hematological response at 6 months compared to rabbit ATG (68% versus 37%).¹⁶ Superior survival was also seen with horse ATG compared to rabbit ATG (3-year OS: 96% versus 76%). Due to these results, horse ATG is preferred over rabbit ATG. ATG should be used in combination with cyclosporine A to optimize outcomes.

Cyclosporine A. Early studies also demonstrated the efficacy of cyclosporine A in the treatment of aplastic anemia, with response rates equivalent to that of ATG monotherapy.³⁹ Recent publications still note the efficacy of cyclosporine A in the treatment of aplastic anemia. Its role as an affordable option for single-agent therapy in developing countries is intriguing.³⁹

The combination of the ATG and cyclosporine A was proven superior to either agent alone in a study by Frickhofen et al.³⁷ In this study patients were randomly assigned to a control arm that received ATG plus methylprednisolone or to an arm that received ATG plus cyclosporine A and methylprednisolone. At 6 months, 70% of patients in the cyclosporine A arm had a complete remission (CR) or partial remission compared to 46% in the control arm.⁴⁰ Further work confirmed the long-term efficacy of this regimen, reporting a 7-year OS of 55%.⁴¹ Among a pediatric population, immunosuppressive therapy was associated with an 83% 10-year OS.⁴²

It is recommended that patients remain on cyclosporine therapy for a minimum of 6 months, after which a gradual taper may be considered, although there is variation among practitioners, with some continuing immunosuppressive therapy for a minimum of 12 months due to a proportion of patients being cyclosporine dependent.^42,43 A study found that within a population of patients who responded to immunosuppressive therapy, 18% became cyclosporine dependent.⁴² The median duration of cyclosporine A treatment at full dose was 12 months, with tapering completed over a median of 19 months after patients had been in a stable CR for a minimum of 3 months. Relapse occurred more often when patients were tapered quickly (decrease ≥ 0.8 mg/kg/month) compared to slowly (0.4-0.7 mg/kg/month) or very slowly (< 0.3 mg/kg/month).

Immunosuppressive therapy plus eltrombopag. Townsley and colleagues recently investigated incorporating the use of the thrombopoietin receptor agonist eltrombopag with immunosuppressive therapy as first-line therapy in aplastic anemia.⁴⁴ When given at a dose of 150 mg daily in patients aged 12 years and older or 75 mg daily in patients younger than 12 years, in conjunction with cyclosporine A and ATG, patients demonstrated markedly improved hematological response compared to historical treatment with standard immunosuppressive therapy alone.⁴⁴ In the patient cohort administered eltrombopag starting on day 1 and continuing for 6 months, the complete response rate was 58%. Eltrombopag led to improvement in all cell lines among all treatment subgroups, and OS (censored for patients who proceeded to transplant) was 99% at 2 years.⁴⁵ Overall, toxicities associated with this therapy were low, with liver enzyme elevations most commonly observed.⁴⁴ Recently, a phase 2 trial of immunosuppressive therapy with or without eltrombopag was reported. Of the 38 patients enrolled, overall response, complete response, and time to response were not statistically different.⁴⁶ With this recent finding, the role of eltrombopag in addition to immunosuppressive therapy is not clearly defined, and further studies are warranted.

OS for patients who do not respond to immunosuppressive therapy is approximately 57% at 5 years, largely due to improved supportive measures among this patient population.^4,22 Therefore, it is important to recognize those patients who have a low chance of response so that second-line therapy can be pursued to improve outcomes.

Matched Unrelated Donor Transplant

For patients with refractory disease following immunosuppressive therapy who lack a matched sibling donor, MUD HSCT is considered standard therapy given the marked improvement in overall outcomes with modulating conditioning regimens and high-resolution HLA typing. A European Society for Blood and Marrow Transplantation analysis comparing matched sibling HSCT to MUD HSCT noted significantly higher rates of acute grade II-IV and grade III-V GVHD (grade II-IV 13% versus 25%, grade III-IV 5% versus 10%) among patients undergoing MUD transplant.⁴⁷ Chronic GVHD rates were 14% in the sibling group, as compared to 26% in the MUD group. Additional benefits seen in this analysis included improved survival when transplanted under age 20 years (84% versus 72%), when transplanted within 6 months of diagnosis (85% versus 72%), the use of ATG in the conditioning regimen (81% versus 73%), and when the donor and recipient were cytomegalovirus-negative compared to other combinations (82% versus 76%).⁴⁷ Interestingly, this study demonstrated that OS was not significantly increased when using a sibling HSCT compared to a MUD HSCT, likely as a result of improved understanding of conditioning regimens, GVHD prophylaxis, and supportive care.

Additional studies of MUD HSCT have shown outcomes similar to those seen in sibling HSCT.^4,43 A French study found a significant increase in survival in patients undergoing MUD HSCT compared to historical cohorts (2000-2005: OS 52%; 2006-2012: OS 74%).³³ The majority of patients underwent conditioning with cyclophosphamide or a combination of busulfan and cyclophosphamide, with or without fludarabine; 81% of patients included underwent in vivo T-cell depletion, and a bone marrow donor source was utilized. OS was significantly lower in patients over age 30 years undergoing MUD HSCT (57%) compared to those under age 30 years (70%). Improved OS was also seen when patients underwent transplant within 1 year of diagnosis and when a 10/10 matched donor (compared to a 9/10 mismatched donor) was utilized.⁴ A 2015 study investigated the role of MUD HSCT as frontline therapy instead of immunosuppressive therapy in patients without a matched sibling donor.³³ The 2-year OS was 96% in the MUD HSCT cohort compared to 91%, 94%, and 74% in historical cohorts of sibling HSCT, frontline immunosuppressive therapy, and second-line MUD HSCT following failed immunosuppressive therapy, respectively. Additionally, event-free survival in the MUD HSCT cohort (defined by the authors as death, lack of response, relapse, occurrence of clonal evolution/clinical paroxysmal nocturnal hemoglobinuria, malignancies developing over follow‐up, and transplant for patients receiving immunosuppressive therapy frontline) was similar compared to sibling HSCT and superior to frontline immunosuppressive therapy and second-line MUD HSCT. Furthermore, Samarasinghe et al highlighted the importance of in vivo T-cell depletion with either ATG or alemtuzumab (anti-CD52 monoclonal antibody) in the prevention of acute and chronic GVHD in both sibling HSCT and MUD HSCT.⁴⁸

With continued improvement of less toxic and more immunomodulating conditioning regimens, utilization of bone marrow as a donor cell source, in vivo T-cell depletion, and use of GVHD and antimicrobial prophylaxis, more clinical evidence supports elevating MUD HSCT in the treatment plan for patients without a matched sibling donor.⁴⁹ However, there is still a large population of patients without matched sibling or unrelated donor options. In an effort to expand the transplant pool and thus avoid clonal hematopoiesis, clinically significant paroxysmal nocturnal hemoglobinuria, and relapsed aplastic anemia, more work continues to recognize the expanding role of alternative donor transplants (cord blood and haploidentical) as another viable treatment strategy for aplastic anemia after immunosuppressive therapy failure.⁵⁰

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. Treatment should be instituted as soon as the dignosis of aplastic anemia is established. Treatment outcomes are excellent with modern supportive care and the current approach to allogeneic transplantation, and therefore referral to a bone marrow transplant program to evaluate for early transplantation is the new standard of care.

Breast cancer survivors should continue to be monitored for hematologic malignancies, especially acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), results of a population-based study from France suggest.

Among nearly 440,000 women with an incident breast cancer diagnosis, the incidence of AML was nearly three times higher and the incidence of MDS was five times higher than that of women in the general population. Women with breast cancer also were at higher risk for multiple myeloma (MM) and acute lymphoblastic leukemia/lymphocytic lymphoma (ALL/LL) compared with the background population, reported Marie Joelle Jabagi, PharmD, MPH, of the University of Paris Sud, France, and her colleagues.

“These findings serve to better inform practicing oncologists, and breast cancer survivors should be advised of the increased risk of developing certain hematologic malignant neoplasms after their first cancer diagnosis,” they wrote in JAMA Network Open.

Breast cancers are the malignant solid tumors most frequently associated with risk for myeloid neoplasms, but there is little information on the risk for secondary lymphoid malignancies among breast cancer patients, the investigators stated.

“In addition, real-life data on secondary hematologic malignant neoplasm incidence are scarce, especially in the recent period marked by major advances in breast cancer treatments,” they wrote.

To get better estimates of the incidence of myeloid and lymphoid neoplasms in this population, they conducted a retrospective review of information from the French National Health Data System on all French women from the ages of 20 to 85 years who had an incident breast cancer diagnosis from July 1, 2006, through Dec. 31, 2015.

In all, 439,704 women with a median age of 59 years were identified. They were followed until a diagnosis of a hematologic malignancy, death, or loss to follow-up, or until Dec. 31, 2016.

Data on the breast cancer patients were compared with those for all French women in the general population who were registered in the general national health insurance program from January 2007 through the end of 2016.

During a median follow-up of 5 years, there were 3,046 cases of hematologic neoplasms among the breast cancer patients, including 509 cases of AML, for a crude incidence rate (CIR) of 24.5 per 100,000 person-years (py); 832 cases of MDS for a CIR of 40.1/100,000 py; and 267 cases of myeloproliferative neoplasms (MPN), for a CIR of 12.8/100,000 py.

In addition, there were 420 cases of MM for a CIR of 20.3/100,000 py; 912 cases of Hodgkin or non-Hodgkin lymphoma (HL/NHL) for a CIR of 44.4/100,000 py, and 106 cases of ALL/LL for a CIR of 5.1/100,000 py.

Breast cancer survivors had significantly higher incidences, compared with the general population, of AML (standardized incidence ratio [SIR] 2.8, 95% confidence interval [CI], 2.5-3.2), MDS (SIR 5.0, CI, 4.4-5.7), MM (SIR 1.5, CI, 1.3-17), and ALL/LL (SIR 2.0, CI, 1.3-3.0). There was a trend toward significance for both MPN and HL/NHL, but the lower limit of the confidence intervals for these conditions either crossed or touched 1.

In a review of the literature, the authors found that “[s]everal studies linked AML and MDS to chemotherapeutic agents, radiation treatment, and supportive treatment with granulocyte colony-stimulating factor. These results are consistent with other available data showing a 2½-fold to 3½-fold increased risk of AML.”

They noted that their estimate of a five-fold increase in risk for MDS was higher than the 3.7-fold risk reported in a previous registry cohort analysis, suggesting that risk for MDS among breast cancer patients may be underestimated.

“The recent discovery of the gene signatures that guide treatment decisions in early-stage breast cancer might reduce the number of patients exposed to cytotoxic chemotherapy and its complications, including hematologic malignant neoplasm. Therefore, continuing to monitor hematologic malignant neoplasm trends is necessary, especially given that approaches to cancer treatment are rapidly evolving. Further research is also required to assess the modality of treatment for and the genetic predisposition to these secondary malignant neoplasms,” the authors concluded.

SOURCE: Jabagi MJ et al. JAMA Network Open. 2019 Jan 18. doi: 10.1001/jamanetworkopen.2018.7147.

Breast cancer survivors should continue to be monitored for hematologic malignancies, especially acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), results of a population-based study from France suggest.

Among nearly 440,000 women with an incident breast cancer diagnosis, the incidence of AML was nearly three times higher and the incidence of MDS was five times higher than that of women in the general population. Women with breast cancer also were at higher risk for multiple myeloma (MM) and acute lymphoblastic leukemia/lymphocytic lymphoma (ALL/LL) compared with the background population, reported Marie Joelle Jabagi, PharmD, MPH, of the University of Paris Sud, France, and her colleagues.

“These findings serve to better inform practicing oncologists, and breast cancer survivors should be advised of the increased risk of developing certain hematologic malignant neoplasms after their first cancer diagnosis,” they wrote in JAMA Network Open.

Breast cancers are the malignant solid tumors most frequently associated with risk for myeloid neoplasms, but there is little information on the risk for secondary lymphoid malignancies among breast cancer patients, the investigators stated.

“In addition, real-life data on secondary hematologic malignant neoplasm incidence are scarce, especially in the recent period marked by major advances in breast cancer treatments,” they wrote.

To get better estimates of the incidence of myeloid and lymphoid neoplasms in this population, they conducted a retrospective review of information from the French National Health Data System on all French women from the ages of 20 to 85 years who had an incident breast cancer diagnosis from July 1, 2006, through Dec. 31, 2015.

In all, 439,704 women with a median age of 59 years were identified. They were followed until a diagnosis of a hematologic malignancy, death, or loss to follow-up, or until Dec. 31, 2016.

Data on the breast cancer patients were compared with those for all French women in the general population who were registered in the general national health insurance program from January 2007 through the end of 2016.

During a median follow-up of 5 years, there were 3,046 cases of hematologic neoplasms among the breast cancer patients, including 509 cases of AML, for a crude incidence rate (CIR) of 24.5 per 100,000 person-years (py); 832 cases of MDS for a CIR of 40.1/100,000 py; and 267 cases of myeloproliferative neoplasms (MPN), for a CIR of 12.8/100,000 py.

In addition, there were 420 cases of MM for a CIR of 20.3/100,000 py; 912 cases of Hodgkin or non-Hodgkin lymphoma (HL/NHL) for a CIR of 44.4/100,000 py, and 106 cases of ALL/LL for a CIR of 5.1/100,000 py.

Breast cancer survivors had significantly higher incidences, compared with the general population, of AML (standardized incidence ratio [SIR] 2.8, 95% confidence interval [CI], 2.5-3.2), MDS (SIR 5.0, CI, 4.4-5.7), MM (SIR 1.5, CI, 1.3-17), and ALL/LL (SIR 2.0, CI, 1.3-3.0). There was a trend toward significance for both MPN and HL/NHL, but the lower limit of the confidence intervals for these conditions either crossed or touched 1.

In a review of the literature, the authors found that “[s]everal studies linked AML and MDS to chemotherapeutic agents, radiation treatment, and supportive treatment with granulocyte colony-stimulating factor. These results are consistent with other available data showing a 2½-fold to 3½-fold increased risk of AML.”

They noted that their estimate of a five-fold increase in risk for MDS was higher than the 3.7-fold risk reported in a previous registry cohort analysis, suggesting that risk for MDS among breast cancer patients may be underestimated.

“The recent discovery of the gene signatures that guide treatment decisions in early-stage breast cancer might reduce the number of patients exposed to cytotoxic chemotherapy and its complications, including hematologic malignant neoplasm. Therefore, continuing to monitor hematologic malignant neoplasm trends is necessary, especially given that approaches to cancer treatment are rapidly evolving. Further research is also required to assess the modality of treatment for and the genetic predisposition to these secondary malignant neoplasms,” the authors concluded.

SOURCE: Jabagi MJ et al. JAMA Network Open. 2019 Jan 18. doi: 10.1001/jamanetworkopen.2018.7147.

Breast cancer survivors should continue to be monitored for hematologic malignancies, especially acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), results of a population-based study from France suggest.

Among nearly 440,000 women with an incident breast cancer diagnosis, the incidence of AML was nearly three times higher and the incidence of MDS was five times higher than that of women in the general population. Women with breast cancer also were at higher risk for multiple myeloma (MM) and acute lymphoblastic leukemia/lymphocytic lymphoma (ALL/LL) compared with the background population, reported Marie Joelle Jabagi, PharmD, MPH, of the University of Paris Sud, France, and her colleagues.

“These findings serve to better inform practicing oncologists, and breast cancer survivors should be advised of the increased risk of developing certain hematologic malignant neoplasms after their first cancer diagnosis,” they wrote in JAMA Network Open.

Breast cancers are the malignant solid tumors most frequently associated with risk for myeloid neoplasms, but there is little information on the risk for secondary lymphoid malignancies among breast cancer patients, the investigators stated.

“In addition, real-life data on secondary hematologic malignant neoplasm incidence are scarce, especially in the recent period marked by major advances in breast cancer treatments,” they wrote.

To get better estimates of the incidence of myeloid and lymphoid neoplasms in this population, they conducted a retrospective review of information from the French National Health Data System on all French women from the ages of 20 to 85 years who had an incident breast cancer diagnosis from July 1, 2006, through Dec. 31, 2015.

In all, 439,704 women with a median age of 59 years were identified. They were followed until a diagnosis of a hematologic malignancy, death, or loss to follow-up, or until Dec. 31, 2016.

Data on the breast cancer patients were compared with those for all French women in the general population who were registered in the general national health insurance program from January 2007 through the end of 2016.

During a median follow-up of 5 years, there were 3,046 cases of hematologic neoplasms among the breast cancer patients, including 509 cases of AML, for a crude incidence rate (CIR) of 24.5 per 100,000 person-years (py); 832 cases of MDS for a CIR of 40.1/100,000 py; and 267 cases of myeloproliferative neoplasms (MPN), for a CIR of 12.8/100,000 py.

In addition, there were 420 cases of MM for a CIR of 20.3/100,000 py; 912 cases of Hodgkin or non-Hodgkin lymphoma (HL/NHL) for a CIR of 44.4/100,000 py, and 106 cases of ALL/LL for a CIR of 5.1/100,000 py.

Breast cancer survivors had significantly higher incidences, compared with the general population, of AML (standardized incidence ratio [SIR] 2.8, 95% confidence interval [CI], 2.5-3.2), MDS (SIR 5.0, CI, 4.4-5.7), MM (SIR 1.5, CI, 1.3-17), and ALL/LL (SIR 2.0, CI, 1.3-3.0). There was a trend toward significance for both MPN and HL/NHL, but the lower limit of the confidence intervals for these conditions either crossed or touched 1.

In a review of the literature, the authors found that “[s]everal studies linked AML and MDS to chemotherapeutic agents, radiation treatment, and supportive treatment with granulocyte colony-stimulating factor. These results are consistent with other available data showing a 2½-fold to 3½-fold increased risk of AML.”

They noted that their estimate of a five-fold increase in risk for MDS was higher than the 3.7-fold risk reported in a previous registry cohort analysis, suggesting that risk for MDS among breast cancer patients may be underestimated.

“The recent discovery of the gene signatures that guide treatment decisions in early-stage breast cancer might reduce the number of patients exposed to cytotoxic chemotherapy and its complications, including hematologic malignant neoplasm. Therefore, continuing to monitor hematologic malignant neoplasm trends is necessary, especially given that approaches to cancer treatment are rapidly evolving. Further research is also required to assess the modality of treatment for and the genetic predisposition to these secondary malignant neoplasms,” the authors concluded.

SOURCE: Jabagi MJ et al. JAMA Network Open. 2019 Jan 18. doi: 10.1001/jamanetworkopen.2018.7147.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Aplastic anemia is a clinical and pathological entity of bone marrow failure that causes progressive loss of hematopoietic progenitor stem cells (HPSC), resulting in pancytopenia.¹ Patients may present along a spectrum, ranging from being asymptomatic with incidental findings on peripheral blood testing to having life-threatening neutropenic infections or bleeding. Aplastic anemia results from either inherited or acquired causes, and the pathophysiology and treatment approach vary significantly between these 2 causes. Therefore, recognition of inherited marrow failure diseases, such as Fanconi anemia and telomere biology disorders, is critical to establishing the management plan. This article reviews the epidemiology, pathophysiology, clinical presentation, and diagnosis of aplastic anemia. Treatment of aplastic anemia is reviewed in a separate article.

Epidemiology

Aplastic anemia is a rare disorder, with an incidence of approximately 1.5 to 7 cases per million individuals per year.^2,3 A recent Scandinavian study reported that the incidence of aplastic anemia among the Swedish population is 2.3 cases per million individuals per year, with a median age at diagnosis of 60 years and a slight female predominance (52% versus 48%, respectively).² This data is congruent with prior observations made in Barcelona, where the incidence was 2.34 cases per million individuals per year, albeit with a slightly higher incidence in males compared to females (2.54 versus 2.16, respectively).⁴ The incidence of aplastic anemia varies globally, with a disproportionate increase in incidence seen among Asian populations, with rates as high as 8.8 per million individuals per year.^3-5 This variation in incidence in Asia versus other countries has not been well explained. There appears to be a bimodal distribution, with incidence peaks seen in young adults and in older adults.^2,3,6

Pathophysiology

Acquired Aplastic Anemia

The leading hypothesis as to the cause of most cases of acquired aplastic anemia is that a dysregulated immune system destroys hematopoietic progenitor cells. Inciting etiologies implicated in the development of acquired aplastic anemia include pregnancy, infection, medications, and exposure to certain chemicals, such as benzene.^1,7 The historical understanding of acquired aplastic anemia implicates cytotoxic T-lymphocyte–mediated destruction of CD34+ hematopoietic stem cells.^1,8,9 This hypothesis served as the basis for treatment of acquired aplastic anemia with immunosuppressive therapy, predominantly anti-thymocyte globulin (ATG) combined with cyclosporine A.^1,8 More recent work has focused on cytokine interactions, particularly the suppressive role of interferon (IFN)-γ on hematopoietic stem cells independent of T-lymphocyte–mediated hematopoietic destruction, which has been demonstrated in a murine model.⁸ The interaction of IFN-γ with the hematopoietic stem cells pool is dynamic. IFN-γ levels are elevated during an acute inflammatory response such as a viral infection, providing further basis for the immune-mediated nature of the acquired disease.¹⁰ Specifically, in vitro studies suggest the effects of IFN-γ on HPSC may be secondary to interruption of thrombopoietin and its respective signaling pathways, which play a key role in hematopoietic stem cell renewal.¹¹ Eltrombopag, a thrombopoietin receptor antagonist, has shown promise in the treatment of refractory aplastic anemia, with studies indicating that its effectiveness is independent of IFN-γ levels.^11,12

Inherited Aplastic Anemia

The inherited marrow failure syndromes (IMFSs) are a group of disorders characterized by cellular maintenance and repair defects, leading to cytopenias, increased cancer risk, structural defects, and risk of end organ damage, such as liver cirrhosis and pulmonary fibrosis.^13-15 The most common diseases include Fanconi anemia, dyskeratosis congenita/telomere biology disorders, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome, but with the advent of whole exome sequencing new syndromes continue to be discovered. While classically these disorders present in children, adult presentations of these syndromes are now commonplace. Broadly, the pathophysiology of inherited aplastic anemia relates to the defective hematopoietic progenitor cells and an accelerated decline of the hematopoietic stem cell compartment.

The most common IMFS, Fanconi anemia and telomere biology disorders, are associated with numerous mutations in DNA damage repair pathways and telomere maintenance pathways. TERT, DKC, and TERC mutations are most commonly associated with dyskeratosis congenita, but may also be found infrequently in patients with aplastic anemia presenting at an older age in the absence of the classic phenotypical features.^1,16,17 The recognition of an underlying genetic disorder or telomere biology disorder leading to constitutional aplastic anemia is significant, as these conditions are associated not only with marrow failure, but also endocrinopathies, organ fibrosis, and solid organ malignancies.^13-15 In particular, mutations in the TERT and TERC genes have been associated with dyskeratosis congenita as well as pulmonary fibrosis and cirrhosis.^18,19 The implications of early diagnosis of an IMFS lie in the approach to treatment and prognosis.

Clonal Disorders and Secondary Malignancies

Myelodysplastic syndrome (MDS) and secondary acute myeloid leukemia (AML) are 2 clonal disorders that may arise from a background of aplastic anemia.^9,20,21 Hypoplastic MDS can be difficult to differentiate from aplastic anemia at diagnosis based on morphology alone, although recent work has demonstrated that molecular testing for somatic mutations in ASXL1, DNMT3A, and BCOR can aid in differentiating a subset of aplastic anemia patients who are more likely to progress to MDS.²¹ Clonal populations of cells harboring 6p uniparental disomy are seen in more than 10% of patients with aplastic anemia on cytogenetic analysis, which can help differentiate the diseases.⁹ Yoshizato and colleagues found lower rates of ASXL1 and DNMT3A mutations in patients with aplastic anemia as compared with patients with MDS or AML. In this study, patients with aplastic anemia had higher rates of mutations in PIGA (reflecting the increased paroxysmal nocturnal hemoglobinuria [PNH] clonality seen in aplastic anemia) and BCOR.⁹ Mutations were also found in genes commonly mutated in MDS and AML, including TET2, RUNX1, TP53, and JAK2, albeit at lower frequencies.⁹ These mutations as a whole have not predicted response to therapy or prognosis. However, when performing survival analysis in patients with specific mutations, those commonly encountered in MDS/AML (ASXL1, DNMT3A, TP53, RUNX1, CSMD1) are associated with faster progression to overt MDS/AML and decreased overall survival (OS),^20,21 suggesting these mutations may represent early clonality that can lead to clonal evolution and the development of secondary malignancies. Conversely, mutations in BCOR and BCORL appear to identify patients who may have a favorable outcome in response to immunosuppressive therapy and, similar to patients with PIGA mutations, improved OS.⁹

Paroxysmal Nocturnal Hemoglobinuria

In addition to having an increased risk of myelodysplasia and malignancy due to the development of a dominant pre-malignant clone, patients with aplastic anemia often harbor progenitor cell clones associated with PNH.^1,17 PNH clones have been identified in more than 50% of patients with aplastic anemia.^22,23 PNH represents a clonal disorder of hematopoiesis in which cells harbor X-linked somatic mutations in the PIGA gene; this gene encodes a protein responsible for the synthesis of glycosylphosphatidylinositol (GPI) anchors on the cell surface.^22,24 The lack of these cell surface proteins, specifically CD55 (also known as decay accelerating factor) and CD59 (also known as membrane inhibitor of reactive lysis), predisposes red cells to increased complement-mediated lysis.²⁵ The exact mechanism for the development of these clones in patients with aplastic anemia is not fully understood. Current theories hypothesize that these clones are protected from the immune-mediated destruction of normal hematopoietic stem cells due to the absence of the cell surface proteins.^1,20 The role of these clones over time in patients with aplastic anemia is less clear, though recent work demonstrated that despite differences in clonality over the disease course, aplastic anemia patients with small PNH clones are less likely to develop overt hemolysis and larger PNH clones compared to patients harboring larger (≥ 50%) PNH clones at diagnosis.^23,26,27 Additionally, PNH clones in patients with aplastic anemia infrequently become clinically significant.²⁷ It should be noted that these conditions exist along a continuum; that is, patients with aplastic anemia may develop PNH clones, while conversely patients with PNH may develop aplastic anemia.²⁰ Patients with PNH clones should be followed via peripheral blood flow cytometry in addition to complete blood count to track clonal stability and identify clinically significant PNH among aplastic anemia patients.²⁸

Patients with aplastic anemia typically are diagnosed either due to asymptomatic cytopenias found on peripheral blood sampling, symptomatic anemia, bleeding secondary to thrombocytopenia, or wound healing and infectious complications related to neutropenia.²⁹ A thorough history to understand the timing of symptoms, recent infectious symptoms/exposure, habits, and chemical or toxin exposures (including medications, travel, and supplements) helps guide diagnostic testing. Family history is also critical, with attention given to premature graying, pulmonary, renal, and liver disease, and blood disorders.

Patients with an IMFS, (eg, Fanconi anemia or dyskeratosis congenita) may have associated phenotypical findings such as urogenital abnormalities or short stature; in addition, those with dyskeratosis congenita may present with the classic triad of oral leukoplakia, lacy skin pigmentation, and dystrophic nails.⁷ However, in patients with IMFS, classic phenotypical findings may be lacking in up to 30% to 40% of patients.⁷ As described previously, while congenital malformations are common in Fanconi anemia and dyskeratosis congenita, a third of patients may have no or only subtle phenotypical abnormalities, including alterations in skin or hair pigmentation, skeletal and growth abnormalities, and endocrine disorders.³⁰ The International Fanconi Anemia Registry identified central nervous system, genitourinary, skin and musculoskeletal, ophthalmic, and gastrointestinal system malformations among children with Fanconi anemia.^31,32 Patients with dyskeratosis congenita may present with pulmonary fibrosis, hepatic cirrhosis, or premature graying, as highlighted in a recent study by DiNardo and colleagues.³³ Therefore, physicians must have a heightened index of suspicion in patients with subtle phenotypical findings and associated cytopenias.

Diagnosis

Differential Diagnosis

The diagnosis of aplastic anemia should be suspected in any patient presenting with pancytopenia. Aplastic anemia is a diagnosis of exclusion.³⁴ Other conditions associated with peripheral blood pancytopenia should be considered including infections (HIV, hepatitis, parvovirus B19, cytomegalovirus, Epstein-Barr virus, varicella-zoster virus), nutritional deficiencies (vitamin B12, folate, copper, zinc), autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, hemophagocytic lymphohistiocytosis), hypersplenism, marrow-occupying diseases (eg, leukemia, lymphoma, MDS), solid malignancies, and fibrosis (Table).⁷

Diagnostic Evaluation

The workup for aplastic anemia should include a thorough history and physical exam to search simultaneously for alternative diagnoses and clues pointing to potential etiologic agents.⁷ Diagnostic tests to be performed include a complete blood count with differential, reticulocyte count, immature platelet fraction, flow cytometry (to rule out lymphoproliferative disorders and atypical myeloid cells and to evaluate for PNH), and bone marrow biopsy with subsequent cytogenetic, immunohistochemical, and molecular testing.³⁵ The typical findings in aplastic anemia include peripheral blood pancytopenia without dysplastic features and bone marrow biopsy demonstrating a hypocellular marrow.⁷ A relative lymphocytosis in the peripheral blood is common.⁷ In patients with a significant PNH clone, a macrocytosis along with elevated lactate dehydrogenase and elevated reticulocyte and granulocyte counts may be present.³⁶

The diagnosis (based on the Camitta criteria³⁷ and modified Camitta criteria³⁸ for severe aplastic anemia) requires 2 of the following findings on peripheral blood samples:

• Absolute neutrophil count (ANC) < 500 cells/µL
• Platelet count < 20,000 cells/µL
• Reticulocyte count < 1% corrected or < 20,000 cells/µL.³⁵

In addition to peripheral blood findings, bone marrow biopsy is essential for the diagnosis, and should demonstrate a markedly hypocellular marrow (cellularity < 25%), occasionally with an increase in T lymphocytes.^7,39 Because marrow cellularity varies with age and can be challenging to assess, additional biopsies may be needed to confirm the diagnosis.²⁹ A 1- to 2-cm core biopsy is necessary to confirm hypocellularity, as small areas of residual hematopoiesis may be present and obscure the diagnosis.³⁵

Excluding Hypocellular MDS and IMFS

A diagnostic challenge is the exclusion of hypocellular MDS, especially in the older adult presenting with aplastic anemia, as patients with aplastic anemia may have some degree of erythroid dysplasia on bone marrow morphology.³⁶ The presence of a PNH clone on flow cytometry can aid in diagnosing aplastic anemia and excluding MDS,³⁴ although PNH clones can be present in refractory anemia MDS. Patients with aplastic anemia have a lower ratio of CD34+ cells compared to those with hypoplastic MDS, with one study demonstrating a mean CD34+ percentage of < 0.5% in aplastic anemia versus 3.7% in hypoplastic MDS.⁴⁰ Cytogenetic and molecular testing can also aid in making this distinction by identifying mutations commonly implicated in MDS.⁷ The presence of monosomy 7 (-7) in aplastic anemia patients is associated with a poor overall prognosis.^34,41

Peripheral blood screening using chromosome breakage analysis (done using either mitomycin C or diepoxybutane as in vitro DNA-crosslinking agents) and telomere length testing (of peripheral blood leukocytes) is necessary to exclude the main IMFS, Fanconi anemia and telomere biology disorders, respectively. Ruling out these conditions is imperative, as the approach to treatment varies significantly between IMFS and aplastic anemia. Patients with shortened telomeres should undergo genetic screening for mutations in the telomere maintenance genes to evaluate the underlying defect leading to shortened telomeres. Patients with increased peripheral blood breakage should have genetic testing to detect mutations associated with Fanconi anemia.

Classification

Once the diagnosis of aplastic anemia has been made, the patient should be classified according to the severity of their disease. Disease severity is determined based on peripheral blood ANC:³⁴ non-severe aplastic anemia (NSAA), ANC > 500 polymorphonuclear neutrophils (PMNs)/µL; severe aplastic anemia (SAA), 200–500 PMNs/µL; and very severe (VSAA), 0–200 PMNs/µL.^4,34 Disease classification is important, as VSAA is associated with a decreased OS compared to SAA.² Disease classification may affect treatment decisions, as patients with NSAA may be observed for a short period of time, while conversely patients with SAA have a worse prognosis with delays in therapy.^42-44

Summary

Aplastic anemia is a rare but potentially life-threatening disorder characterized by pancytopenia and a marked reduction in the hematopoietic stem cell compartment. It can be acquired or associated with an IMFS, and the treatment and prognosis vary dramatically between these 2 etiologies. Work-up and diagnosis involves investigating IMFSs and ruling out malignant or infectious etiologies for pancytopenia. After aplastic anemia has been diagnosed, the patient should be classified according to the severity of their disease based on peripheral blood ANC.

Two different obinutuzumab-based chemoimmunotherapy regimens resulted in excellent long-term disease control as front-line therapy for chronic lymphocytic leukemia (CLL), investigators said in a follow-up report on a phase 1b study.

©Ed Uthman/Flickr

Both obinutuzumab plus fludarabine/cyclophosphamide (G-FC) and obinutuzumab plus bendamustine (G-B) were well tolerated, with adverse events similar to what has been reported in rituximab-containing immunotherapy regimens, they said in the report of final results from the GALTON trial.

Most evaluable patients had B-cell recovery by 36 months in the study, which included a population of CLL patients largely without 17p deletions, said Jennifer R. Brown, MD, PhD, of Dana-Farber Cancer Institute, Boston, and her coinvestigators.

“These data support moving forward with these regimens in subsequent trials, which are currently ongoing,” they said in their report on the study, which appears in Blood.

The open-label, parallel-arm, multicenter phase 1b GALTON study included 41 patients with CLL, of whom 21 received G-FC and 20 received G-B for up to six cycles of 28 days each. The median age was 60 years, and about one-third of patients had Rai stage III or IV disease. Only one patient had del(17p), and nearly half of patients tested (17 of 38 patients) had unmutated immunoglobulin heavy-chain variable region gene (IGHV). Six patients had del(11q), including four in the G-FC arm and two in the G-B arm.

Both G-FC and G-B had manageable toxicities, with infusion-related reactions being the most common adverse event, occurring in 88% (20% grade 3 or 4), Dr. Brown and her colleagues reported, adding that grade 3 or 4 neutropenia was seen in 48% of the G-FC arm and 55% of the G-B arm.

The objective response rate (ORR) was 62% for G-FC and 90% for GB.

“The ORR in the G-FC arm likely does not reflect the true activity of the regimen, as it is based on an intent-to-treat analysis,” the investigators said.

With a median observation time of 40.4 months, 95% of patients were alive, and 90% had not experienced a progression-free survival event.

Nine patients in the G-FC arm underwent minimal residual disease (MRD) testing in peripheral blood; 100% had undetectable MRD, according to the report.

“With the caveat of small patient numbers and inevitable differences in patient populations across studies, these results suggest that G-FC may clear residual disease more effectively than rituximab plus FC,” the investigators wrote.

Previous studies of R-FC showed an undetectable MRD rate of 45% or less, they said.

The study was sponsored by Genentech. The investigators reported disclosures related to Genentech/Roche and other companies.

SOURCE: Brown JR et al. Blood. 2018 Dec 28. doi: 10.1182/blood-2018-06-857714.

Two different obinutuzumab-based chemoimmunotherapy regimens resulted in excellent long-term disease control as front-line therapy for chronic lymphocytic leukemia (CLL), investigators said in a follow-up report on a phase 1b study.

©Ed Uthman/Flickr

Both obinutuzumab plus fludarabine/cyclophosphamide (G-FC) and obinutuzumab plus bendamustine (G-B) were well tolerated, with adverse events similar to what has been reported in rituximab-containing immunotherapy regimens, they said in the report of final results from the GALTON trial.

Most evaluable patients had B-cell recovery by 36 months in the study, which included a population of CLL patients largely without 17p deletions, said Jennifer R. Brown, MD, PhD, of Dana-Farber Cancer Institute, Boston, and her coinvestigators.

“These data support moving forward with these regimens in subsequent trials, which are currently ongoing,” they said in their report on the study, which appears in Blood.

The open-label, parallel-arm, multicenter phase 1b GALTON study included 41 patients with CLL, of whom 21 received G-FC and 20 received G-B for up to six cycles of 28 days each. The median age was 60 years, and about one-third of patients had Rai stage III or IV disease. Only one patient had del(17p), and nearly half of patients tested (17 of 38 patients) had unmutated immunoglobulin heavy-chain variable region gene (IGHV). Six patients had del(11q), including four in the G-FC arm and two in the G-B arm.

Both G-FC and G-B had manageable toxicities, with infusion-related reactions being the most common adverse event, occurring in 88% (20% grade 3 or 4), Dr. Brown and her colleagues reported, adding that grade 3 or 4 neutropenia was seen in 48% of the G-FC arm and 55% of the G-B arm.

The objective response rate (ORR) was 62% for G-FC and 90% for GB.

“The ORR in the G-FC arm likely does not reflect the true activity of the regimen, as it is based on an intent-to-treat analysis,” the investigators said.

With a median observation time of 40.4 months, 95% of patients were alive, and 90% had not experienced a progression-free survival event.

Nine patients in the G-FC arm underwent minimal residual disease (MRD) testing in peripheral blood; 100% had undetectable MRD, according to the report.

“With the caveat of small patient numbers and inevitable differences in patient populations across studies, these results suggest that G-FC may clear residual disease more effectively than rituximab plus FC,” the investigators wrote.

Previous studies of R-FC showed an undetectable MRD rate of 45% or less, they said.

The study was sponsored by Genentech. The investigators reported disclosures related to Genentech/Roche and other companies.

SOURCE: Brown JR et al. Blood. 2018 Dec 28. doi: 10.1182/blood-2018-06-857714.

Two different obinutuzumab-based chemoimmunotherapy regimens resulted in excellent long-term disease control as front-line therapy for chronic lymphocytic leukemia (CLL), investigators said in a follow-up report on a phase 1b study.

©Ed Uthman/Flickr

Both obinutuzumab plus fludarabine/cyclophosphamide (G-FC) and obinutuzumab plus bendamustine (G-B) were well tolerated, with adverse events similar to what has been reported in rituximab-containing immunotherapy regimens, they said in the report of final results from the GALTON trial.

Most evaluable patients had B-cell recovery by 36 months in the study, which included a population of CLL patients largely without 17p deletions, said Jennifer R. Brown, MD, PhD, of Dana-Farber Cancer Institute, Boston, and her coinvestigators.

“These data support moving forward with these regimens in subsequent trials, which are currently ongoing,” they said in their report on the study, which appears in Blood.

The open-label, parallel-arm, multicenter phase 1b GALTON study included 41 patients with CLL, of whom 21 received G-FC and 20 received G-B for up to six cycles of 28 days each. The median age was 60 years, and about one-third of patients had Rai stage III or IV disease. Only one patient had del(17p), and nearly half of patients tested (17 of 38 patients) had unmutated immunoglobulin heavy-chain variable region gene (IGHV). Six patients had del(11q), including four in the G-FC arm and two in the G-B arm.

Both G-FC and G-B had manageable toxicities, with infusion-related reactions being the most common adverse event, occurring in 88% (20% grade 3 or 4), Dr. Brown and her colleagues reported, adding that grade 3 or 4 neutropenia was seen in 48% of the G-FC arm and 55% of the G-B arm.

The objective response rate (ORR) was 62% for G-FC and 90% for GB.

“The ORR in the G-FC arm likely does not reflect the true activity of the regimen, as it is based on an intent-to-treat analysis,” the investigators said.

With a median observation time of 40.4 months, 95% of patients were alive, and 90% had not experienced a progression-free survival event.

Nine patients in the G-FC arm underwent minimal residual disease (MRD) testing in peripheral blood; 100% had undetectable MRD, according to the report.

“With the caveat of small patient numbers and inevitable differences in patient populations across studies, these results suggest that G-FC may clear residual disease more effectively than rituximab plus FC,” the investigators wrote.

Previous studies of R-FC showed an undetectable MRD rate of 45% or less, they said.

The study was sponsored by Genentech. The investigators reported disclosures related to Genentech/Roche and other companies.

SOURCE: Brown JR et al. Blood. 2018 Dec 28. doi: 10.1182/blood-2018-06-857714.

The Food and Drug Administration has approved calaspargase pegol-mknl (Asparlas) as a component of a multiagent chemotherapy regimen to treat acute lymphoblastic leukemia (ALL) in pediatric and young adult patients aged 1 month to 21 years.

Calaspargase pegol-mknl is an asparagine-specific enzyme intended to provide a longer interval between doses, compared with other available pegaspargase products. The recommended dosage of calaspargase pegol-mknl is 2,500 units/m² given no more frequently than every 21 days.

The FDA said it approved calaspargase pegol-mknl because the drug maintained nadir serum asparaginase activity above the level of 0.1 U/mL when given at 2,500 U/m² every 3 weeks.

Calaspargase pegol-mknl was evaluated in Study DFCI 11-001, a trial of 237 children and adolescents with newly diagnosed ALL or lymphoblastic lymphoma. The patients’ median age was 5 years.

Study participants received calaspargase pegol-mknl at 2,500 U/m² (n = 118) or pegaspargase at 2,500 U/m² (n = 119) as part of a Dana-Farber Cancer Institute ALL Consortium backbone therapy. The median duration of exposure was 8 months for both calaspargase pegol-mknl and pegaspargase. Among the patients with B-cell lineage ALL, the complete remission rate was 98% in the calaspargase pegol-mknl arm and 99% in the pegaspargase arm. Estimated overall survival rates were comparable between the arms.

Common grade 3 or higher adverse events in the calaspargase pegol-mknl and pegaspargase arms included elevated transaminase (52% and 66%, respectively), bilirubin increase (20% and 25%), pancreatitis (18% and 24%), and abnormal clotting studies (14% and 21%). There was one fatal adverse event among patients on calaspargase pegol-mknl – multiorgan failure in the setting of chronic pancreatitis associated with a pancreatic pseudocyst.

The safety of calaspargase pegol-mknl was also evaluated in Study AALL07P4, a trial of patients with newly diagnosed, high-risk B-precursor ALL. The patients received calaspargase pegol-mknl at 2,500 U/m² (n = 43) or 2,100 U/m² (n = 68) or pegaspargase at 2,500 U/m² (n = 52) as a component of an augmented Berlin-Frankfurt-Münster regimen. The patients’ median age was 11 years. The median duration of exposure was 7 months for both calaspargase pegol-mknl and pegaspargase. There were 3 induction deaths among the 111 patients who received calaspargase pegol-mknl (2.8%) but no induction deaths among the 52 patients treated with pegaspargase.

Additional details on these studies and calaspargase pegol-mknl can be found in the drug’s prescribing information. Calaspargase pegol-mknl is a product of Servier.

[email protected]

The Food and Drug Administration has approved calaspargase pegol-mknl (Asparlas) as a component of a multiagent chemotherapy regimen to treat acute lymphoblastic leukemia (ALL) in pediatric and young adult patients aged 1 month to 21 years.

Calaspargase pegol-mknl is an asparagine-specific enzyme intended to provide a longer interval between doses, compared with other available pegaspargase products. The recommended dosage of calaspargase pegol-mknl is 2,500 units/m² given no more frequently than every 21 days.

The FDA said it approved calaspargase pegol-mknl because the drug maintained nadir serum asparaginase activity above the level of 0.1 U/mL when given at 2,500 U/m² every 3 weeks.

Calaspargase pegol-mknl was evaluated in Study DFCI 11-001, a trial of 237 children and adolescents with newly diagnosed ALL or lymphoblastic lymphoma. The patients’ median age was 5 years.

Study participants received calaspargase pegol-mknl at 2,500 U/m² (n = 118) or pegaspargase at 2,500 U/m² (n = 119) as part of a Dana-Farber Cancer Institute ALL Consortium backbone therapy. The median duration of exposure was 8 months for both calaspargase pegol-mknl and pegaspargase. Among the patients with B-cell lineage ALL, the complete remission rate was 98% in the calaspargase pegol-mknl arm and 99% in the pegaspargase arm. Estimated overall survival rates were comparable between the arms.

Common grade 3 or higher adverse events in the calaspargase pegol-mknl and pegaspargase arms included elevated transaminase (52% and 66%, respectively), bilirubin increase (20% and 25%), pancreatitis (18% and 24%), and abnormal clotting studies (14% and 21%). There was one fatal adverse event among patients on calaspargase pegol-mknl – multiorgan failure in the setting of chronic pancreatitis associated with a pancreatic pseudocyst.

The safety of calaspargase pegol-mknl was also evaluated in Study AALL07P4, a trial of patients with newly diagnosed, high-risk B-precursor ALL. The patients received calaspargase pegol-mknl at 2,500 U/m² (n = 43) or 2,100 U/m² (n = 68) or pegaspargase at 2,500 U/m² (n = 52) as a component of an augmented Berlin-Frankfurt-Münster regimen. The patients’ median age was 11 years. The median duration of exposure was 7 months for both calaspargase pegol-mknl and pegaspargase. There were 3 induction deaths among the 111 patients who received calaspargase pegol-mknl (2.8%) but no induction deaths among the 52 patients treated with pegaspargase.

Additional details on these studies and calaspargase pegol-mknl can be found in the drug’s prescribing information. Calaspargase pegol-mknl is a product of Servier.

[email protected]

The Food and Drug Administration has approved calaspargase pegol-mknl (Asparlas) as a component of a multiagent chemotherapy regimen to treat acute lymphoblastic leukemia (ALL) in pediatric and young adult patients aged 1 month to 21 years.

Calaspargase pegol-mknl is an asparagine-specific enzyme intended to provide a longer interval between doses, compared with other available pegaspargase products. The recommended dosage of calaspargase pegol-mknl is 2,500 units/m² given no more frequently than every 21 days.

The FDA said it approved calaspargase pegol-mknl because the drug maintained nadir serum asparaginase activity above the level of 0.1 U/mL when given at 2,500 U/m² every 3 weeks.

Calaspargase pegol-mknl was evaluated in Study DFCI 11-001, a trial of 237 children and adolescents with newly diagnosed ALL or lymphoblastic lymphoma. The patients’ median age was 5 years.

Study participants received calaspargase pegol-mknl at 2,500 U/m² (n = 118) or pegaspargase at 2,500 U/m² (n = 119) as part of a Dana-Farber Cancer Institute ALL Consortium backbone therapy. The median duration of exposure was 8 months for both calaspargase pegol-mknl and pegaspargase. Among the patients with B-cell lineage ALL, the complete remission rate was 98% in the calaspargase pegol-mknl arm and 99% in the pegaspargase arm. Estimated overall survival rates were comparable between the arms.

Common grade 3 or higher adverse events in the calaspargase pegol-mknl and pegaspargase arms included elevated transaminase (52% and 66%, respectively), bilirubin increase (20% and 25%), pancreatitis (18% and 24%), and abnormal clotting studies (14% and 21%). There was one fatal adverse event among patients on calaspargase pegol-mknl – multiorgan failure in the setting of chronic pancreatitis associated with a pancreatic pseudocyst.

The safety of calaspargase pegol-mknl was also evaluated in Study AALL07P4, a trial of patients with newly diagnosed, high-risk B-precursor ALL. The patients received calaspargase pegol-mknl at 2,500 U/m² (n = 43) or 2,100 U/m² (n = 68) or pegaspargase at 2,500 U/m² (n = 52) as a component of an augmented Berlin-Frankfurt-Münster regimen. The patients’ median age was 11 years. The median duration of exposure was 7 months for both calaspargase pegol-mknl and pegaspargase. There were 3 induction deaths among the 111 patients who received calaspargase pegol-mknl (2.8%) but no induction deaths among the 52 patients treated with pegaspargase.

Additional details on these studies and calaspargase pegol-mknl can be found in the drug’s prescribing information. Calaspargase pegol-mknl is a product of Servier.

[email protected]