After publication of the American College of Surgeons Z0011 trial, we are seeing more patients with positive lymph nodes who have not undergone an axillary lymph node dissection. What are the optimal radiation treatment fields for patients with early breast cancer who undergo a lumpectomy and sentinel lymph node dissection and are found to have a positive sentinel lymph node?
Completion axillary lymph node dissection (ALND) has been the historical standard for patients with positive sentinel lymph nodes. The benefits of axillary dissection are twofold. First, 25%-50% of patients with sentinel lymph node-positive disease will have additional axillary lymph node involvement, and resection of these lymph nodes is an effective approach to eradicating disease. Second, ALND allows quantification of the number of involved lymph nodes, which provides prognostic information and forms the basis for determining pathological stage of disease. Unfortunately, however, ALND is not without serious sequelae. For example, nearly all patients who have undergone ALND experience paresthesias and temporary shoulder range-of-motion abnormalities. Of greater importance, ALND also places patients at an increased risk for the development of lymphedema.
To avoid these consequences, investigators from the American College of Surgeons designed a cooperative group phase 3 randomized trial (Z0011) to investigate the clinical value of axillary dissection for patients with positive sentinel lymph node(s). The results of this trial, which were recently published,[1] have already had an impact on clinical care patterns in the United States.[ 1,2] Accordingly, it is important for all breast cancer practitioners to be well informed about this trial, including both its positive findings and its limitations. The trial included patients with clinical T1/2 N0 breast cancers who were found to have 1 or 2 positive sentinel lymph nodes. Patients were then randomly assigned to either no further axillary treatment and standard whole breast radiation with tangent fields or a completion axillary dissection and whole breast radiation. The original trial design called for 1900 patients but, due to slow accrual, enrolled only 891 and closed prematurely. The patients enrolled in the study had many favorable characteristics: median age was 55 years, 69% had T1 disease, 80% had estrogen receptor-positive disease, 65% had only 1 positive sentinel lymph node, and 96% received systemic treatments.
The results of Z0011 indicated that 27% of the patients who underwent axillary dissection actually had additional axillary disease. Because this was a randomized, well-balanced study, it could be predicted that those who did not have an axillary dissection would nevertheless have a similar rate of additional axillary disease that was not treated surgically. Despite this, after a median follow-up period of 6.3 years, the regional recurrence rate was only 0.5% in the patients who did not have an ALND. This rate was not different from that seen in the axillary dissection cohort, and the survival rates and local-regional control rates were likewise very similar. There was, however, a lower rate of lymphedema in patients who did not undergo ALND.[3] Based on these data, it is now appropriate to consider avoiding completion axillary dissection in patients treated with breast-conserving surgery, whole breast radiation, and who have similar favorable characteristics as the patients enrolled in Z0011. The benefits of omitting an axillary dissection are significant both for patients (eg, lower morbidity risk, avoidance of an axillary drain, shorter postsurgical rehabilitation) and healthcare systems (eg, avoidance of intraoperative assessment of sentinel lymph nodes and second surgical procedures, decreased healthcare costs).
How radiation oncologists should treat patients with positive sentinel lymph nodes and no axillary dissection remains uncertain. To determine the optimal radiation approach, it is helpful to speculate about the reasons for the very low axillary recurrence rate -- 0.5% -- despite the predicted 27% rate of additional axillary involvement. It is possible that systemic treatments have some effect in preventing disease recurrence. However, the rate of pathological eradication of involved axillary lymph nodes with neoadjuvant chemotherapy is only about 20%-40%.[4] It is also possible that the tangent radiation fields used to treat the breast also treated the low axilla and exerted a therapeutic effect. Indeed, numerous studies have shown that a high percentage of the axillary level I/II is included within tangent breast radiation fields.[5-7] Furthermore, with relatively minor adjustments to these fields (ie, making the tangents 1-2 cm higher in length and 1 cm deeper in the cranial corners -- sometimes called a "high tangent" technique), these fields can include most of the same volume that is treated with a completion axillary dissection.[5-8] Finally, radiation is known to be highly effective in eradicating subclinical foci of disease within lymph nodes. The percentage of the axilla treated with radiation in the Z0011 trial cannot be determined because the radiation treatment fields used in the study were not described.
My preference in selecting radiation fields for patients similar to those included in the Z0011 trial is to use a high tangent technique. This is optimally done with CT treatment planning, in which the axillary level I/II can be contoured and included in the tangent breast fields used to treat the breast only, with relatively small modifications. This technique assures that the area at risk for residual lymph node disease is included in the fields and that adequate dose is provided to this region. While this technique has never been directly compared with standard breast tangents, it is likely that they would yield very similar risks for normal tissue consequences. It should also be noted that the results of Z0011 are applicable only for patients treated with breast conservation and whole breast radiation. Patients treated with mastectomy or breast conservation with partial breast radiation would not receive the potentially beneficial effects of axillary radiation and therefore may be at a higher risk for disease recurrence. Therefore, such patients are recommended to undergo completion axillary dissection.
Completion axillary lymph node dissection (ALND) has been the historical standard for patients with positive sentinel lymph nodes. The benefits of axillary dissection are twofold. First, 25%-50% of patients with sentinel lymph node-positive disease will have additional axillary lymph node involvement, and resection of these lymph nodes is an effective approach to eradicating disease. Second, ALND allows quantification of the number of involved lymph nodes, which provides prognostic information and forms the basis for determining pathological stage of disease. Unfortunately, however, ALND is not without serious sequelae. For example, nearly all patients who have undergone ALND experience paresthesias and temporary shoulder range-of-motion abnormalities. Of greater importance, ALND also places patients at an increased risk for the development of lymphedema.
To avoid these consequences, investigators from the American College of Surgeons designed a cooperative group phase 3 randomized trial (Z0011) to investigate the clinical value of axillary dissection for patients with positive sentinel lymph node(s). The results of this trial, which were recently published,[1] have already had an impact on clinical care patterns in the United States.[ 1,2] Accordingly, it is important for all breast cancer practitioners to be well informed about this trial, including both its positive findings and its limitations. The trial included patients with clinical T1/2 N0 breast cancers who were found to have 1 or 2 positive sentinel lymph nodes. Patients were then randomly assigned to either no further axillary treatment and standard whole breast radiation with tangent fields or a completion axillary dissection and whole breast radiation. The original trial design called for 1900 patients but, due to slow accrual, enrolled only 891 and closed prematurely. The patients enrolled in the study had many favorable characteristics: median age was 55 years, 69% had T1 disease, 80% had estrogen receptor-positive disease, 65% had only 1 positive sentinel lymph node, and 96% received systemic treatments.
The results of Z0011 indicated that 27% of the patients who underwent axillary dissection actually had additional axillary disease. Because this was a randomized, well-balanced study, it could be predicted that those who did not have an axillary dissection would nevertheless have a similar rate of additional axillary disease that was not treated surgically. Despite this, after a median follow-up period of 6.3 years, the regional recurrence rate was only 0.5% in the patients who did not have an ALND. This rate was not different from that seen in the axillary dissection cohort, and the survival rates and local-regional control rates were likewise very similar. There was, however, a lower rate of lymphedema in patients who did not undergo ALND.[3] Based on these data, it is now appropriate to consider avoiding completion axillary dissection in patients treated with breast-conserving surgery, whole breast radiation, and who have similar favorable characteristics as the patients enrolled in Z0011. The benefits of omitting an axillary dissection are significant both for patients (eg, lower morbidity risk, avoidance of an axillary drain, shorter postsurgical rehabilitation) and healthcare systems (eg, avoidance of intraoperative assessment of sentinel lymph nodes and second surgical procedures, decreased healthcare costs).
How radiation oncologists should treat patients with positive sentinel lymph nodes and no axillary dissection remains uncertain. To determine the optimal radiation approach, it is helpful to speculate about the reasons for the very low axillary recurrence rate -- 0.5% -- despite the predicted 27% rate of additional axillary involvement. It is possible that systemic treatments have some effect in preventing disease recurrence. However, the rate of pathological eradication of involved axillary lymph nodes with neoadjuvant chemotherapy is only about 20%-40%.[4] It is also possible that the tangent radiation fields used to treat the breast also treated the low axilla and exerted a therapeutic effect. Indeed, numerous studies have shown that a high percentage of the axillary level I/II is included within tangent breast radiation fields.[5-7] Furthermore, with relatively minor adjustments to these fields (ie, making the tangents 1-2 cm higher in length and 1 cm deeper in the cranial corners -- sometimes called a "high tangent" technique), these fields can include most of the same volume that is treated with a completion axillary dissection.[5-8] Finally, radiation is known to be highly effective in eradicating subclinical foci of disease within lymph nodes. The percentage of the axilla treated with radiation in the Z0011 trial cannot be determined because the radiation treatment fields used in the study were not described.
My preference in selecting radiation fields for patients similar to those included in the Z0011 trial is to use a high tangent technique. This is optimally done with CT treatment planning, in which the axillary level I/II can be contoured and included in the tangent breast fields used to treat the breast only, with relatively small modifications. This technique assures that the area at risk for residual lymph node disease is included in the fields and that adequate dose is provided to this region. While this technique has never been directly compared with standard breast tangents, it is likely that they would yield very similar risks for normal tissue consequences. It should also be noted that the results of Z0011 are applicable only for patients treated with breast conservation and whole breast radiation. Patients treated with mastectomy or breast conservation with partial breast radiation would not receive the potentially beneficial effects of axillary radiation and therefore may be at a higher risk for disease recurrence. Therefore, such patients are recommended to undergo completion axillary dissection.
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