Should carotid body tumors be embolized preoperatively?

 

Preop embolization is safe and effective

To embolize or not to embolize ... that is the question when it comes to the management of carotid body tumors. Carotid body tumors (CBTs) are rare benign neoplasms that are almost always nonfunctional and account for up to 80% of all head and neck paragangliomas. Radiographic characteristics include tumor location at the carotid bifurcation, splaying apart the internal and external carotid arteries. Surgical resection is the mainstay of definitive treatment and is preferably performed at diagnosis. CBTs are categorized based upon their involvement with surrounding structures: Shamblin I tumors are small, without encasement of the carotid arteries; Shamblin II tumors partially encase the vessels; and Shamblin III tumors completely encase the vessels. When it comes to operative complications, advanced Shamblin stage is associated with a higher rate of cranial nerve injury when the tumor is resected.¹

Pertinent to the technical aspects of surgical resection, CBTs are characteristically encased with an elaborate network of friable vessels which may contribute to significant intraoperative bleeding, especially with resection of larger tumors. The blood supply to CBTs typically originates from the branches of the external carotid artery. These branches may be sacrificed with minimal consequence using preoperative embolization. This common practice is felt by many to facilitate safe resection while minimizing intraoperative blood loss. Although the reduction of blood loss has not been observed universally, there is enough evidence of this in the literature to support the use of selective preoperative embolization. Several embolic agents have been described in this setting, including polyvinyl alcohol particles (150-1000 microns), polymerized glue (n-butyl cyanoacrylate), and more recently, ethylene-vinyl alcohol copolymer (Onyx, ev3, Irvine, Calif.). Risks of complications related to CBT embolization in experienced hands are quite low with no adverse events reported in a number of reports describing the technique.^2,3

Numerous published series have demonstrated the safety and efficacy of CBT embolization, which is typically performed 1-3 days prior to surgical resection. One large study showed a 50% reduction in the operative blood loss associated with resection after embolization.⁴ This study also noted a reduction in the need for internal carotid artery clamping and a higher likelihood of a simple excision when embolization was performed preoperatively. A retrospective review of over 2,000 patients undergoing surgical resection of CBTs in the Nationwide Inpatient Sample showed potential benefit of preoperative embolization with significant reduction in hematoma formation and need for transfusion when compared with outcomes in patients requiring carotid reconstruction as part of their tumor excision, presumably in more advanced tumors.⁵

Although embolization is argued to decrease blood loss, its impact on rates of neurologic complications is admittedly insignificant. One might question the added cost of the embolization procedure in the current atmosphere of focus on cost-containment, but this may be defrayed by lower rates of postoperative hematoma and operative times. Although blood loss has been shown to be decreased in a number of reports, translating this to decreased need for transfusion has unfortunately yet to be demonstrated. Until large-volume prospective randomized studies of the outcomes associated with preoperative embolization of CBTs are available, its use should be considered mainly when risks of blood loss are significant in advanced stage tumors and only if the associated complication risks associated with its use can be kept to acceptably low rates. As with other adjunctive procedures whose merit has not yet been convincingly sorted out in the available data, personal experience and preference often play a role in the decision making process we all face. For those who have experienced the added challenge of the meticulous dissection of the CBT in the face of a bloodied field, having such tools as embolization at our fingertips is a reassuring adjunct to be considered.

References

1. J Vasc Surg. 2013;57:64-8S.

2. J Vasc Interv Neurol. 2008;1(2):37-41.

3. Am J Neuroradiol. 2009;30:1594-97.

4. J Vasc Surg. 2012;56:979-89.

5. Vasc Endovasc Surg. 2009;43:457-61.

Too many downsides

As vascular surgeons, we are frequently confronting situations where the “best” approach to a problem is far from established. The evidence to make a clinical decision may simply not exist, and we need to choose a course of therapy based more on personal preference than science. Such is the case with preoperative embolization for the resection of carotid body tumors (CBT).

It has been over 35 years since the technique for preoperative embolization of CBT was described, the aim being reduction in blood loss, decreased operative time, and improved visualization for safer tumor resection. This is based on the fact that most of the arterial supply to these tumors arises from external carotid branches (particularly the ascending pharyngeal), and these that can be safely sacrificed. Although this technique is certainly now a standard part of treatment for many vascular surgeons, the evidence of benefit is certainly not overwhelming, and like all interventions, nothing comes without risks.

Proponents of preoperative embolization cite reduced operative blood loss as a principal reason for this strategy. There are studies supporting this concept, although it is not a universal finding in the CBT literature. In fact, a 2016 meta-analysis of 15 CBT treatment reports demonstrated no significant difference in blood loss in patients undergoing preoperative embolization. Importantly, even in studies demonstrating this reduction in blood loss, it is not usually accompanied by a reduction in transfusion need. Of course, the blood loss itself is not the only proposed benefit of embolization. Advocates also cite that the better control of these vessels going into the case provides a “blood free” operative field, and this in turn leads to a “safer” resection. Certainly, the ability to decrease the incidence of cranial nerve injury would be an important clinical endpoint to strive for. Again, the CBT literature is not clear as to whether preoperative embolization decreases the incidence of such nerve injuries. This is partially related to the wide range of reported cranial nerve injuries (ranging from 7%-40%), as well as the failure of many reports to comment on cranial nerve injury. So, as with blood loss itself, the impact of preoperative embolization on cranial nerve injury has not been defined.

So what are the downsides of preoperative embolization? The cost of the procedure itself is not insignificant, in some cases doubling the expense of the intervention. And there can also be organizational issues with coordinating the time in the endovascular suite versus the operating room. In my experience, we have taken patients directly from embolization for the CBT resection, and there are frequently delays and transport issues. Although advocates may claim decreased operative time as a benefit of embolization, this is attained at an overall increase in anesthetic time for the combined procedures. If a day or two separates the procedures, some patients do report the pain or fevers that can accompany any tumor embolization.

While the above may be nuisances, there are serious adverse effects from preoperative embolization as well. A review of 11 studies of preoperative embolization for CBT found a 2.5% rate of complications, including temporary aphasia, vocal cord paralysis, and arterial dissection. Stroke with permanent deficit has also been reported secondary to CBT embolization. Access site hematoma has also been reported as with any catheter-based intervention.

With regards to “selective” preoperative embolization, the literature again offers a mixed bag. Many advocates of embolization rely upon the Shamblin classification for selecting candidates, reserving embolization for Shamblin II and III tumors. However, the extent of carotid involvement is sometimes a surgical diagnosis. Although size of tumor generally correlates with Shamblin class, even smaller tumors can demonstrate arterial wall involvement. Abu-Ghanem provides a succinct review of the uncertainty regarding size, Shamblin class, and the impact these have on cranial nerve injury.² The bottom line is that there is no data-based algorithm for deciding whom to select for preoperative embolization.

In the absence of compelling data for the use of preoperative embolization, this technique is difficult to recommend. There are undoubtedly cases with giant CBTs where a surgeon will want to take advantage of any preoperative adjuvant therapy that is available. However, for the vast majority of CBTs, the important principles are to stay in the correct plane, identify and protect the nerves at risk, and control the tumor blood supply in a systematic fashion. In the absence of a forthcoming randomized prospective study to evaluate preoperative embolization for CBT resection, I will rely on the wisdom of my mentor, Dr. Wesley Moore. He never utilized preoperative embolization for these cases. At least not that he will admit to me.
 

References

1. Surgery. 1980;87:459-464.

2. Head Neck. 2016;38:E2386-E2394.

3. J Vasc Surg. 2015;61:1081-91.

4. Otolaryngol Head Neck Surg. 2015;153:942-950.

 

Preop embolization is safe and effective

To embolize or not to embolize ... that is the question when it comes to the management of carotid body tumors. Carotid body tumors (CBTs) are rare benign neoplasms that are almost always nonfunctional and account for up to 80% of all head and neck paragangliomas. Radiographic characteristics include tumor location at the carotid bifurcation, splaying apart the internal and external carotid arteries. Surgical resection is the mainstay of definitive treatment and is preferably performed at diagnosis. CBTs are categorized based upon their involvement with surrounding structures: Shamblin I tumors are small, without encasement of the carotid arteries; Shamblin II tumors partially encase the vessels; and Shamblin III tumors completely encase the vessels. When it comes to operative complications, advanced Shamblin stage is associated with a higher rate of cranial nerve injury when the tumor is resected.¹

Pertinent to the technical aspects of surgical resection, CBTs are characteristically encased with an elaborate network of friable vessels which may contribute to significant intraoperative bleeding, especially with resection of larger tumors. The blood supply to CBTs typically originates from the branches of the external carotid artery. These branches may be sacrificed with minimal consequence using preoperative embolization. This common practice is felt by many to facilitate safe resection while minimizing intraoperative blood loss. Although the reduction of blood loss has not been observed universally, there is enough evidence of this in the literature to support the use of selective preoperative embolization. Several embolic agents have been described in this setting, including polyvinyl alcohol particles (150-1000 microns), polymerized glue (n-butyl cyanoacrylate), and more recently, ethylene-vinyl alcohol copolymer (Onyx, ev3, Irvine, Calif.). Risks of complications related to CBT embolization in experienced hands are quite low with no adverse events reported in a number of reports describing the technique.^2,3

Numerous published series have demonstrated the safety and efficacy of CBT embolization, which is typically performed 1-3 days prior to surgical resection. One large study showed a 50% reduction in the operative blood loss associated with resection after embolization.⁴ This study also noted a reduction in the need for internal carotid artery clamping and a higher likelihood of a simple excision when embolization was performed preoperatively. A retrospective review of over 2,000 patients undergoing surgical resection of CBTs in the Nationwide Inpatient Sample showed potential benefit of preoperative embolization with significant reduction in hematoma formation and need for transfusion when compared with outcomes in patients requiring carotid reconstruction as part of their tumor excision, presumably in more advanced tumors.⁵

Although embolization is argued to decrease blood loss, its impact on rates of neurologic complications is admittedly insignificant. One might question the added cost of the embolization procedure in the current atmosphere of focus on cost-containment, but this may be defrayed by lower rates of postoperative hematoma and operative times. Although blood loss has been shown to be decreased in a number of reports, translating this to decreased need for transfusion has unfortunately yet to be demonstrated. Until large-volume prospective randomized studies of the outcomes associated with preoperative embolization of CBTs are available, its use should be considered mainly when risks of blood loss are significant in advanced stage tumors and only if the associated complication risks associated with its use can be kept to acceptably low rates. As with other adjunctive procedures whose merit has not yet been convincingly sorted out in the available data, personal experience and preference often play a role in the decision making process we all face. For those who have experienced the added challenge of the meticulous dissection of the CBT in the face of a bloodied field, having such tools as embolization at our fingertips is a reassuring adjunct to be considered.

References

1. J Vasc Surg. 2013;57:64-8S.

2. J Vasc Interv Neurol. 2008;1(2):37-41.

3. Am J Neuroradiol. 2009;30:1594-97.

4. J Vasc Surg. 2012;56:979-89.

5. Vasc Endovasc Surg. 2009;43:457-61.

Too many downsides

As vascular surgeons, we are frequently confronting situations where the “best” approach to a problem is far from established. The evidence to make a clinical decision may simply not exist, and we need to choose a course of therapy based more on personal preference than science. Such is the case with preoperative embolization for the resection of carotid body tumors (CBT).

It has been over 35 years since the technique for preoperative embolization of CBT was described, the aim being reduction in blood loss, decreased operative time, and improved visualization for safer tumor resection. This is based on the fact that most of the arterial supply to these tumors arises from external carotid branches (particularly the ascending pharyngeal), and these that can be safely sacrificed. Although this technique is certainly now a standard part of treatment for many vascular surgeons, the evidence of benefit is certainly not overwhelming, and like all interventions, nothing comes without risks.

Proponents of preoperative embolization cite reduced operative blood loss as a principal reason for this strategy. There are studies supporting this concept, although it is not a universal finding in the CBT literature. In fact, a 2016 meta-analysis of 15 CBT treatment reports demonstrated no significant difference in blood loss in patients undergoing preoperative embolization. Importantly, even in studies demonstrating this reduction in blood loss, it is not usually accompanied by a reduction in transfusion need. Of course, the blood loss itself is not the only proposed benefit of embolization. Advocates also cite that the better control of these vessels going into the case provides a “blood free” operative field, and this in turn leads to a “safer” resection. Certainly, the ability to decrease the incidence of cranial nerve injury would be an important clinical endpoint to strive for. Again, the CBT literature is not clear as to whether preoperative embolization decreases the incidence of such nerve injuries. This is partially related to the wide range of reported cranial nerve injuries (ranging from 7%-40%), as well as the failure of many reports to comment on cranial nerve injury. So, as with blood loss itself, the impact of preoperative embolization on cranial nerve injury has not been defined.

So what are the downsides of preoperative embolization? The cost of the procedure itself is not insignificant, in some cases doubling the expense of the intervention. And there can also be organizational issues with coordinating the time in the endovascular suite versus the operating room. In my experience, we have taken patients directly from embolization for the CBT resection, and there are frequently delays and transport issues. Although advocates may claim decreased operative time as a benefit of embolization, this is attained at an overall increase in anesthetic time for the combined procedures. If a day or two separates the procedures, some patients do report the pain or fevers that can accompany any tumor embolization.

While the above may be nuisances, there are serious adverse effects from preoperative embolization as well. A review of 11 studies of preoperative embolization for CBT found a 2.5% rate of complications, including temporary aphasia, vocal cord paralysis, and arterial dissection. Stroke with permanent deficit has also been reported secondary to CBT embolization. Access site hematoma has also been reported as with any catheter-based intervention.

With regards to “selective” preoperative embolization, the literature again offers a mixed bag. Many advocates of embolization rely upon the Shamblin classification for selecting candidates, reserving embolization for Shamblin II and III tumors. However, the extent of carotid involvement is sometimes a surgical diagnosis. Although size of tumor generally correlates with Shamblin class, even smaller tumors can demonstrate arterial wall involvement. Abu-Ghanem provides a succinct review of the uncertainty regarding size, Shamblin class, and the impact these have on cranial nerve injury.² The bottom line is that there is no data-based algorithm for deciding whom to select for preoperative embolization.

In the absence of compelling data for the use of preoperative embolization, this technique is difficult to recommend. There are undoubtedly cases with giant CBTs where a surgeon will want to take advantage of any preoperative adjuvant therapy that is available. However, for the vast majority of CBTs, the important principles are to stay in the correct plane, identify and protect the nerves at risk, and control the tumor blood supply in a systematic fashion. In the absence of a forthcoming randomized prospective study to evaluate preoperative embolization for CBT resection, I will rely on the wisdom of my mentor, Dr. Wesley Moore. He never utilized preoperative embolization for these cases. At least not that he will admit to me.
 

References

1. Surgery. 1980;87:459-464.

2. Head Neck. 2016;38:E2386-E2394.

3. J Vasc Surg. 2015;61:1081-91.

4. Otolaryngol Head Neck Surg. 2015;153:942-950.

 

Preop embolization is safe and effective

To embolize or not to embolize ... that is the question when it comes to the management of carotid body tumors. Carotid body tumors (CBTs) are rare benign neoplasms that are almost always nonfunctional and account for up to 80% of all head and neck paragangliomas. Radiographic characteristics include tumor location at the carotid bifurcation, splaying apart the internal and external carotid arteries. Surgical resection is the mainstay of definitive treatment and is preferably performed at diagnosis. CBTs are categorized based upon their involvement with surrounding structures: Shamblin I tumors are small, without encasement of the carotid arteries; Shamblin II tumors partially encase the vessels; and Shamblin III tumors completely encase the vessels. When it comes to operative complications, advanced Shamblin stage is associated with a higher rate of cranial nerve injury when the tumor is resected.¹

Pertinent to the technical aspects of surgical resection, CBTs are characteristically encased with an elaborate network of friable vessels which may contribute to significant intraoperative bleeding, especially with resection of larger tumors. The blood supply to CBTs typically originates from the branches of the external carotid artery. These branches may be sacrificed with minimal consequence using preoperative embolization. This common practice is felt by many to facilitate safe resection while minimizing intraoperative blood loss. Although the reduction of blood loss has not been observed universally, there is enough evidence of this in the literature to support the use of selective preoperative embolization. Several embolic agents have been described in this setting, including polyvinyl alcohol particles (150-1000 microns), polymerized glue (n-butyl cyanoacrylate), and more recently, ethylene-vinyl alcohol copolymer (Onyx, ev3, Irvine, Calif.). Risks of complications related to CBT embolization in experienced hands are quite low with no adverse events reported in a number of reports describing the technique.^2,3

Numerous published series have demonstrated the safety and efficacy of CBT embolization, which is typically performed 1-3 days prior to surgical resection. One large study showed a 50% reduction in the operative blood loss associated with resection after embolization.⁴ This study also noted a reduction in the need for internal carotid artery clamping and a higher likelihood of a simple excision when embolization was performed preoperatively. A retrospective review of over 2,000 patients undergoing surgical resection of CBTs in the Nationwide Inpatient Sample showed potential benefit of preoperative embolization with significant reduction in hematoma formation and need for transfusion when compared with outcomes in patients requiring carotid reconstruction as part of their tumor excision, presumably in more advanced tumors.⁵

Although embolization is argued to decrease blood loss, its impact on rates of neurologic complications is admittedly insignificant. One might question the added cost of the embolization procedure in the current atmosphere of focus on cost-containment, but this may be defrayed by lower rates of postoperative hematoma and operative times. Although blood loss has been shown to be decreased in a number of reports, translating this to decreased need for transfusion has unfortunately yet to be demonstrated. Until large-volume prospective randomized studies of the outcomes associated with preoperative embolization of CBTs are available, its use should be considered mainly when risks of blood loss are significant in advanced stage tumors and only if the associated complication risks associated with its use can be kept to acceptably low rates. As with other adjunctive procedures whose merit has not yet been convincingly sorted out in the available data, personal experience and preference often play a role in the decision making process we all face. For those who have experienced the added challenge of the meticulous dissection of the CBT in the face of a bloodied field, having such tools as embolization at our fingertips is a reassuring adjunct to be considered.

References

1. J Vasc Surg. 2013;57:64-8S.

2. J Vasc Interv Neurol. 2008;1(2):37-41.

3. Am J Neuroradiol. 2009;30:1594-97.

4. J Vasc Surg. 2012;56:979-89.

5. Vasc Endovasc Surg. 2009;43:457-61.

Too many downsides

As vascular surgeons, we are frequently confronting situations where the “best” approach to a problem is far from established. The evidence to make a clinical decision may simply not exist, and we need to choose a course of therapy based more on personal preference than science. Such is the case with preoperative embolization for the resection of carotid body tumors (CBT).

It has been over 35 years since the technique for preoperative embolization of CBT was described, the aim being reduction in blood loss, decreased operative time, and improved visualization for safer tumor resection. This is based on the fact that most of the arterial supply to these tumors arises from external carotid branches (particularly the ascending pharyngeal), and these that can be safely sacrificed. Although this technique is certainly now a standard part of treatment for many vascular surgeons, the evidence of benefit is certainly not overwhelming, and like all interventions, nothing comes without risks.

Proponents of preoperative embolization cite reduced operative blood loss as a principal reason for this strategy. There are studies supporting this concept, although it is not a universal finding in the CBT literature. In fact, a 2016 meta-analysis of 15 CBT treatment reports demonstrated no significant difference in blood loss in patients undergoing preoperative embolization. Importantly, even in studies demonstrating this reduction in blood loss, it is not usually accompanied by a reduction in transfusion need. Of course, the blood loss itself is not the only proposed benefit of embolization. Advocates also cite that the better control of these vessels going into the case provides a “blood free” operative field, and this in turn leads to a “safer” resection. Certainly, the ability to decrease the incidence of cranial nerve injury would be an important clinical endpoint to strive for. Again, the CBT literature is not clear as to whether preoperative embolization decreases the incidence of such nerve injuries. This is partially related to the wide range of reported cranial nerve injuries (ranging from 7%-40%), as well as the failure of many reports to comment on cranial nerve injury. So, as with blood loss itself, the impact of preoperative embolization on cranial nerve injury has not been defined.

So what are the downsides of preoperative embolization? The cost of the procedure itself is not insignificant, in some cases doubling the expense of the intervention. And there can also be organizational issues with coordinating the time in the endovascular suite versus the operating room. In my experience, we have taken patients directly from embolization for the CBT resection, and there are frequently delays and transport issues. Although advocates may claim decreased operative time as a benefit of embolization, this is attained at an overall increase in anesthetic time for the combined procedures. If a day or two separates the procedures, some patients do report the pain or fevers that can accompany any tumor embolization.

While the above may be nuisances, there are serious adverse effects from preoperative embolization as well. A review of 11 studies of preoperative embolization for CBT found a 2.5% rate of complications, including temporary aphasia, vocal cord paralysis, and arterial dissection. Stroke with permanent deficit has also been reported secondary to CBT embolization. Access site hematoma has also been reported as with any catheter-based intervention.

With regards to “selective” preoperative embolization, the literature again offers a mixed bag. Many advocates of embolization rely upon the Shamblin classification for selecting candidates, reserving embolization for Shamblin II and III tumors. However, the extent of carotid involvement is sometimes a surgical diagnosis. Although size of tumor generally correlates with Shamblin class, even smaller tumors can demonstrate arterial wall involvement. Abu-Ghanem provides a succinct review of the uncertainty regarding size, Shamblin class, and the impact these have on cranial nerve injury.² The bottom line is that there is no data-based algorithm for deciding whom to select for preoperative embolization.

In the absence of compelling data for the use of preoperative embolization, this technique is difficult to recommend. There are undoubtedly cases with giant CBTs where a surgeon will want to take advantage of any preoperative adjuvant therapy that is available. However, for the vast majority of CBTs, the important principles are to stay in the correct plane, identify and protect the nerves at risk, and control the tumor blood supply in a systematic fashion. In the absence of a forthcoming randomized prospective study to evaluate preoperative embolization for CBT resection, I will rely on the wisdom of my mentor, Dr. Wesley Moore. He never utilized preoperative embolization for these cases. At least not that he will admit to me.
 

References

1. Surgery. 1980;87:459-464.

2. Head Neck. 2016;38:E2386-E2394.

3. J Vasc Surg. 2015;61:1081-91.

4. Otolaryngol Head Neck Surg. 2015;153:942-950.