Breast Cancer

A New Technique in the Surgical Management of Breast Cancer: Sentinel Node Biopsy

Axillary lymph node dissection has long been a routine part of the staging and treatment of breast cancer. Axillary lymph node dissection is the surgical removal of the lymph nodes in the underarm, after a lumpectomy or mastectomy. The most important predictive factor in early stage disease is the status of the axillary lymph nodes -- that is, whether or not they contain cancer cells, or "micrometastases." It's important to note that aside from this prognostic information, there appears to be little therapeutic benefit gained by axillary node dissection, and its overall impact on survival remains in question.

What's more, the impact of node dissection in clinical decision-making has decreased as indications have broadened for systemic adjuvant therapy (therapy given when the tumor is believed to be local, confined to the breast, or to the breast and local lymph nodes). In other words, knowledge of nodal status may not necessarily change your treatment, since adjuvant therapy is being given today in a wider range of clinical situations.

A variety of microscopic and molecular features of breast cancer tumor cells have been evaluated for their ability to predict nodal status, but there is still no single individual predictor that can define a population of patients who can forego lymph node dissection. Combining predictors (prognostic factors) increases the likelihood of predicting correctly, but this must be done with caution.

While breast surgeons and medical oncologists have long "accepted" the complications of standard axillary node dissection (including chronic arm swelling, pain, and risk of infection), efforts to develop a more tolerable, yet accurate, nodal assessment remain a major focus in the surgical management of breast cancer.

Sentinel node mapping or sentinel lymphadenectomy (SLND) is a new technique in which the initial lymph node at risk for harboring metastatic disease (the "sentinel node") is identified during the operation. If this node is positive for cancer, it can be assumed that the nodes that branch off from this node will also be positive. The reverse also holds true.

Using a combination of blue-staining dye and the radioisotope technetium, the sentinel node can be localized in 93-97% of patients. Furthermore, several institutions have reported large numbers of patients whose sentinel node status has shown a predictive accuracy of 96-100%. These findings have led a number of groups to eliminate routine axillary node dissection in sentinel node-negative patients, thus avoiding the complications of more invasive surgery.

The more difficult question remains how to best manage the sentinel node-positive patient. While the standard of care remains full axillary node dissection, several institutions are evaluating the use of axillary node radiation. Furthermore, given the routine use of adjuvant chemotherapy in this setting, the overall significance of detecting further nodal micrometastases remains unclear.