Current Status of Sentinel Node Surgery in Breast Cancer

The biologic rationale for sentinel lymph node biopsy, although it may ultimately stage the axilla more accurately, is essentially that a positive lymph node represents systemic disease. Removal of axillary lymph nodes is of little, if any, therapeutic value, and most patients with tumors greater than 1 cm are offered chemotherapy regardless of nodal status. Thus, the risks of lymphedema and neurologic deficit outweigh any prognostic information derived from an axillary node dissection when this same information can be accurately obtained in a less invasive, less morbid procedure. Methods of Sentinel Node Resection
Krag and Harlow state that periareolar or subareolar injections do not discover lymph node positivity at the same rate as peritumoral techniques. This makes no sense anatomically as it is thought that the breast drains centripetally toward the subareolar plexus and then out to the lymph nodes. Over 1,000 cases with subareolar, central, or periareolar injection and over 200 with confirmatory axillary node dissection have been reported in the literature-all of which validate that this injection method has one of the best false-negative rates (< 1%) for unifocal operable breast cancer. Several sentinel node trials in multicentric disease further confirm the validity of the subareolar injection technique. Table 1 provides estimates from the literature on average false-negative rates for several injection techniques. Only the subareolar injection method reaches the less than 5% false-negative rate suggested by the Philadelphia consensus conference as being necessary for a surgeon to safely perform sentinel lymph node biopsy alone.[1] Internal Mammary Nodes
The question of whether to evaluate internal mammary nodes will be debated for a long time. The problem for me is that I cannot locate internal mammary lymph nodes regardless of what technique I use. I perform peritumoral injection for National Surgical Adjuvant Breast and Bowel Project (NSABP) B-32 protocol patients, and subareolar injection-first reported by our institution- for American College of Surgeons Oncology Group or nonprotocol patients.[2] I find the same number of internal mammary node localizations- almost zero. It is my hypothesis that surgeons who are performing subareolar injection may inject more slowly in this more sensitive area and more quickly in the less painful, deep parenchymal tissues. A faster injection would mean more pressure and potential backflow instead of natural flow into the internal mammary chain. Training and Certification
One of the major contributions of Krag and Harlow and the Vermont multicenter trial was the creation of a cadre of individuals who were well trained not only in technique but also in proper data-keeping. Such measures are necessary to obtain a meaningful result and to codify the steps in training a given individual.[3] However, Krag and Harlow state that "surgeons in the United States who are not performing any type of sentinel node surgery for breast cancer. . . are in the minority." The National Cancer Data Base shows that advances in breast cancer technology are not rapidly implemented, particularly in rural states and rural areas of more urbanized states.[4] This is confirmed by the still large number of individuals taking training courses in sentinel node strategies and the fact that the American College of Surgeons has developed a sentinel node biopsy mentoring program. Pathologic Evaluation of Sentinel Nodes
Not much had changed in the pathologic evaluation of lymph nodes in the several decades prior to sentinel lymph node biopsy for breast cancer staging. The sentinel node strategy made it feasible to stage a patient intraoperatively using techniques such as frozen section and touch preparation analysis. (The latter is being further validated in the NSABP B-32 trial.)[5,6] That said, the future lies not only in fine-tuning the sentinel node technique but also in being able to preoperatively stage the nodal status of the breast cancer patient.