While most authorities recommend that each surgeon initially perform 20-30 SLN procedures with a backup ALND, fewer validated cases may be necessary. Cox et al found that, to identify the SLN, surgeons required an average of 23 cases to achieve 90% success and 53 cases to achieve 95% success, although the SLN was falsely negative in only 2% of their node-positive patients. We have found that success in localizing the SLN continued to improve over our first 500 cases, and that one-half of our false negative results occurred within the first six cases of each surgeon. A success of 90-95% in finding the SLN and no more than 5-10% false negative results would seem reasonable targets for validation trials. Institutions beginning to perform this procedure should do so under a formalized Institutional Review Board protocol, in which selection and technique are carefully specified, patients are fully informed, a backup axillary dissection is carried out to validate the early experience, and careful audits of individual and institutional results (short and long term) are maintained. The benefit of SLN biopsy seems clear, but the technique is a new one, the long term consequences are not fully defined, and the medicolegal risks are unknown. We have performed more than 3000 SLN biopsy procedures since 1996, and the following represents a distillation of our experience, recently reviewed in detail, and that of other workers. The techniques pertinent to each specialty continue to evolve, and many of these aspects remain the subject of debate. Despite this encouraging debut, SLN biopsy is a new operation, has a definite learning curve, and is highly multidisciplinary, requiring the cooperation of nuclear medicine physicians, surgeons, and pathologists. ![]() An increasing number of centers, having completed validation studies of SLN biopsy, offer patients the option of no further axillary surgery if the SLN is negative. SLNs were identified in 90% of cases, correctly identified 93% of axillary node-positive individuals, and were the only site of nodal metastasis in 47% of these. Among an estimated 184,200 new cases of breast cancer in the United States last year, about 60% (110,000) had disease limited to the breast and might have avoided a conventional axillary lymph node dissection (ALND) through SLN biopsy.īy the end of 1999, 41 peer-reviewed pilot studies using radioisotope or blue dye methods, or a combination of both (Table 1), report the results of SLN biopsy validated by a 'backup' ALND in breast cancer patients. SLN biopsy's immediate potential is greatest among patients with breast cancer, by far the most significant group numerically, and will be the focus of this overview. The procedure has promise but remains investigational in patients with head and neck, urologic, gynecologic, and colorectal cancers. First suggested by Cabanas in the context of penile cancer and conceived in its modern form in a 1992 report by Morton et al, SLN biopsy is rapidly emerging as a new standard of care in melanoma and breast cancer. The hypothesis that one or a few lymph nodes receive the first drainage from a tumor site, and that a regional node dissection and its morbidity might be avoided if the SLNs prove negative, is logical and intuitive. Some of the best ideas in clinical medicine are simple ones, and SLN biopsy is one of these. Retrospective data suggest that micrometastases identified in this way are prognostically significant, and prospective clinical trials now accruing promise a definitive answer to this issue. SLN biopsy for the first time makes enhanced pathologic analysis of lymph nodes logistically feasible, at once allowing greater staging accuracy and less morbidity than standard methods. ![]() SLN biopsy will play a growing role in patients having prophylactic mastectomy, and in those with 'high-risk' duct carcinoma in situ, microinvasive cancers, T3 disease, and neoadjuvant chemotherapy. Most breast cancer patients are suitable for SLN biopsy, and the large majority reported to date has had clinical stage T1-2N0 invasive breast cancers. A combination of isotope and dye to map the SLN is probably superior to either method used alone, yet a wide variety of technical variations in the procedure have produced a striking similarity of results. ![]() At least 90% success in finding the SLN with no more than 5-10% false negative results is a reasonable goal for surgeons and institutions learning the technique. Sentinel lymph node (SLN) biopsy requires validation by a backup axillary dissection in a defined series of cases before becoming standard practice, to establish individual and institutional success rates and the frequency of false negative results.
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