Timing of determining axillary lymph node status when neoadjuvant chemotherapy is used.

Neoadjuvant chemotherapy is the standard of care for patients with locally advanced breast cancer and is a reasonable alternative to adjuvant chemotherapy for those with large operable disease. Potential clinical advantages of neoadjuvant chemotherapy include the conversion of some patients requiring mastectomy to candidates for breast-conserving surgery, the potential for downstaging axillary nodes and thus reducing the extent of axillary surgery, and the ability to correlate clinical and pathologic response to neoadjuvant chemotherapy with improved long-term outcomes. An important and controversial locoregional therapy issue in patients who are candidates for neoadjuvant chemotherapy relates to the timing of sentinel lymph node biopsy - i.e., either before or after neoadjuvant chemotherapy. This review will focus on the performance characteristics of sentinel lymph node biopsy before vs. after neoadjuvant chemotherapy and on the pros and cons of each approach.