Observation of the breast cancer patient with a tumor-positive sentinel node: implications of the ACOSOG Z0011 trial

Axillary lymph node status has been the most important prognostic factor for breast cancer throughout the past century. During the past decade, intraoperative lymphatic mapping with sentinel lymph node dissection (SLND) has been investigated as an alternative staging modality. This technique may be as accurate as ALND, and certainly is less invasive. Adjuvant treatment recommendations, which historically were made on the basis of lymph node status alone, now take into account primary tumor features, molecular markers, and patient characteristics. This evolution of current treatment patterns is driven in part by the diminishing size of tumors, the simultaneous decrease in the presence of axillary metastases, and a better understanding of tumor-specific risk factors. How do these trends affect the interpretation of a tumor-positive sentinel node (SN)? Can an axilla with a positive SN be observed? Should it be observed? This review examines the implications of a positive SN in the context of smaller tumor size, decreased nodal disease, and increased reliance on alternative prognostic factors for treatment decisions. The historical data comparing ALND to no ALND in clinically node-negative patients is reviewed and discussed in the context of observation for a positive SN. These are the issues underlying the ACOSOG Z0010 and Z0011 trials.