Shedding Light on Sentinel Node Biopsy in Breast Cancer
Shedding Light on Sentinel Node Biopsy in Breast Cancer
These studies explore 2 aspects of one of the most rapidly advancing areas in breast cancer management. Only within the past 5 years has sentinel node biopsy for breast cancer emerged as a viable alternative to a full axillary lymph node dissection. As a new technology, its potential to decrease the morbidity associated with a lymph node dissection appears promising, especially in patients with a pathologically neg- ative axilla. However, many questions regarding its precise indications, as well as the treatment recommendations for patients with negative, microscopically positive, or grossly positive sentinel lymph nodes, remain unanswered.
Weaver et al's study is an important one from a group with extensive experience in sentinel node biopsy for breast cancer. A multicenter review of histologic findings in sentinel and nonsentinel nodes was performed in patients who underwent a completion axillary dissection. Disease in 309 of 431 cases was initially characterized as axillary node-negative. All "true-negative" and "false-negative" sentinel node cases were subjected to central review, which reclassified 303 patients as having node-negative disease. In the 385 patients meeting evaluation criteria, the false-negative rate was 3.6%; among 104 patients with a positive sentinel node, 61 patients (59%) had no additional axillary lymph nodes which were positive. Micrometastases, when present, were 12 times more likely to be identified in sentinel nodes than in nonsentinel nodes.
The high degree of correlation in histologic findings between the sites evaluated and central review was encouraging. Moreover, these results further validate the sentinel lymph node concept for breast cancer. It should be noted that the authors of this study used isotope localization only to identify the sentinel lymph node and still reported an excellent success rate of 92%. Other groups that used a combination of blue dye staining and isotope localization have noted a sentinel node identification rate of 92% to 100% compared with 71% to 94% for blue dye staining alone.
The study by Noguchi et al addresses one of the most frequently debated questions in the field of sentinel node biopsy for breast cancer -- the role of internal mammary node biopsy. In this study, 41 consecutive patients underwent sentinel node biopsy for breast cancer, with 19 also undergoing concurrent internal mammary node biopsy. The indications for internal mammary node biopsy are not clearly outlined in the study, but 16 patients had either central or medial lesions. Postoperatively, only 5 of these had positive lymphoscintigraphic findings in the internal mammary region; none demonstrated histologic evidence of metastases.
The internal mammary node was taken between the first and second intercostal spaces in all cases, regardless of tumor location. This may have caused the results of the biopsy to be falsely negative in those patients with lower quadrant lesions. In addition, one critical piece of data was not reported. Although 2 of 19 patients were found to have metastases to the internal mammary node, we do not know if these patients also had concurrent axillary sentinel node metastases. The authors do report a false-negative rate of 5% (2 of 37); it is unlikely, although possible, that these were cases in which the internal mammary node was positive. In those 2 cases in which metastases were found in the internal mammary lymph node, lymphoscintigraphy failed to identify the metastases in both cases and blue dye staining noted metastases in only 1 case.
The data must be considered within the context of previously reported studies, which have demonstrated up to a 20% incidence of positive internal mammary lymph nodes in patients with axillary node-negative breast cancer as well as a decreased mortality rate in those patients with positive internal mammary lymph nodes. Further consideration of this issue is critical because more centers are adopting the use of intradermal injections for sentinel node localization, which are less likely to result in visualization of internal mammary lymph nodes when compared with intraparenchymal injections.
Clearly, a great deal of promising research has been conducted in the field of sentinel node biopsy for breast cancer. However, much remains to be elucidated, and large, prospective clinical trials, such as the one currently under way by the American College of Surgeons, will help establish the role of sentinel node biopsy in treating breast cancer.
These studies explore 2 aspects of one of the most rapidly advancing areas in breast cancer management. Only within the past 5 years has sentinel node biopsy for breast cancer emerged as a viable alternative to a full axillary lymph node dissection. As a new technology, its potential to decrease the morbidity associated with a lymph node dissection appears promising, especially in patients with a pathologically neg- ative axilla. However, many questions regarding its precise indications, as well as the treatment recommendations for patients with negative, microscopically positive, or grossly positive sentinel lymph nodes, remain unanswered.
Weaver et al's study is an important one from a group with extensive experience in sentinel node biopsy for breast cancer. A multicenter review of histologic findings in sentinel and nonsentinel nodes was performed in patients who underwent a completion axillary dissection. Disease in 309 of 431 cases was initially characterized as axillary node-negative. All "true-negative" and "false-negative" sentinel node cases were subjected to central review, which reclassified 303 patients as having node-negative disease. In the 385 patients meeting evaluation criteria, the false-negative rate was 3.6%; among 104 patients with a positive sentinel node, 61 patients (59%) had no additional axillary lymph nodes which were positive. Micrometastases, when present, were 12 times more likely to be identified in sentinel nodes than in nonsentinel nodes.
The high degree of correlation in histologic findings between the sites evaluated and central review was encouraging. Moreover, these results further validate the sentinel lymph node concept for breast cancer. It should be noted that the authors of this study used isotope localization only to identify the sentinel lymph node and still reported an excellent success rate of 92%. Other groups that used a combination of blue dye staining and isotope localization have noted a sentinel node identification rate of 92% to 100% compared with 71% to 94% for blue dye staining alone.
The study by Noguchi et al addresses one of the most frequently debated questions in the field of sentinel node biopsy for breast cancer -- the role of internal mammary node biopsy. In this study, 41 consecutive patients underwent sentinel node biopsy for breast cancer, with 19 also undergoing concurrent internal mammary node biopsy. The indications for internal mammary node biopsy are not clearly outlined in the study, but 16 patients had either central or medial lesions. Postoperatively, only 5 of these had positive lymphoscintigraphic findings in the internal mammary region; none demonstrated histologic evidence of metastases.
The internal mammary node was taken between the first and second intercostal spaces in all cases, regardless of tumor location. This may have caused the results of the biopsy to be falsely negative in those patients with lower quadrant lesions. In addition, one critical piece of data was not reported. Although 2 of 19 patients were found to have metastases to the internal mammary node, we do not know if these patients also had concurrent axillary sentinel node metastases. The authors do report a false-negative rate of 5% (2 of 37); it is unlikely, although possible, that these were cases in which the internal mammary node was positive. In those 2 cases in which metastases were found in the internal mammary lymph node, lymphoscintigraphy failed to identify the metastases in both cases and blue dye staining noted metastases in only 1 case.
The data must be considered within the context of previously reported studies, which have demonstrated up to a 20% incidence of positive internal mammary lymph nodes in patients with axillary node-negative breast cancer as well as a decreased mortality rate in those patients with positive internal mammary lymph nodes. Further consideration of this issue is critical because more centers are adopting the use of intradermal injections for sentinel node localization, which are less likely to result in visualization of internal mammary lymph nodes when compared with intraparenchymal injections.
Clearly, a great deal of promising research has been conducted in the field of sentinel node biopsy for breast cancer. However, much remains to be elucidated, and large, prospective clinical trials, such as the one currently under way by the American College of Surgeons, will help establish the role of sentinel node biopsy in treating breast cancer.
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