Current status of sentinel lymph node surgery for breast cancer.

In 1997, Veronesi et al. (1) reported in the Lancet on their sentinel lymph node experience in a series of 163 patients with breast cancer. The day before surgery, a small volume of colloidal human albumin labeled with technetium 99m was injected subdermally over the tumor in these patients. Gamma camera imaging was performed, and a hand-held gamma probe was used to guide the surgical resection of the sentinel nodes (SNs). The use of blue dye was not reported. In 98% of the cases, at least one SN could be identified surgically. The false-negative rate (i.e., number of cases with negative SNs but positive non-SNs × 100/total number of cases with positive nodes) was 5%. The overall accuracy was 98%. Frozen section analysis had a higher false-negative rate of 36%. Now, this group from Milan reports in this issue of the Journal on 376 cases (i.e., the 163 cases reported in the Lancet plus 213 new cases) (2). The methods were similar to those used for the initial 163 cases. At least one SN was identified in a high percentage of cases (99%). The false-negative rate was slightly higher at 6.7% (12 of 180). These data from Milan highlight three important issues being reported around the world: 1) SNs can be successfully removed in a very high percentage of cases; 2) the accuracy of the SNs for predicting whether axillary metastases have occurred is also very high; but 3) when cancer cells have spread to lymph nodes, the rate at which the SN misses this event is not zero. This important report (2) confirms that the development of the technical aspects of SN surgery has cleared the first hurdle on the way toward clinical utility, but it also confirms that further investigation is warranted. The observation was made early in this century that, in human patients, lymphatic drainage of the abdominal cavity went to “glands sentinel” (3). It has been more than 20 years since the current principles of SN surgery (lymphadenectomy based on the status of the SN) were stated clearly (4). Despite the long opportunity for development, a number of technical issues needed to be resolved in order to apply SN surgery to patients with breast cancer. Blue dye alone, hand-held gamma probeguided resection of radiolabeled SNs, or dye and tracer together achieve a success rate of axillary SN detection exceeding 90%. Thus, a number of options are available for surgical resection of axillary SNs. Successful detection of extra-axillary nodes is a different issue. It is abundantly clear that different individuals can have lymphatic drainage of the breast that follows multiple and varied pathways (5). Even a single individual can have variable lymphatic drainage depending on positioning and local pressure. The notion that lymphatic drainage from a primary breast tumor automatically travels to a single SN in the axilla is overly simplistic. The obvious benefit of SN surgery is that it offers the potential of a much less morbid procedure. The not so obvious potential is that it offers greater accuracy than conventional “blind” axillary lymph node resection. Will decreased morbidity and increased accuracy come with hidden costs? The technical aspects of SN surgery in patients with breast cancer have clearly made the first pass successfully. What are the important issues that now need to be addressed?