Sentinel lymph node biopsy and neoadjuvant chemotherapy in breast cancer patients.

Patient selection and timing of sentinel lymph node (SLN) in the context of primary chemotherapy continues to evolve; there is some evidence that primary chemotherapy may modify lymphatic drainage patterns and cause differential downstaging between SLNs and non-SLNs. SLN biopsy undertaken prior to chemotherapy will minimize the risk of a false-negative result, may allow more accurate initial staging and provides important information on prognostication which can guide decisions about adjuvant radiotherapy. However, quantification of regional metastatic load is incomplete and some advocate SLN biopsy after primary chemotherapy to take advantage of nodal downstaging and avoidance of axillary dissection in up to 40% of patients. Initial reports on false-negative rates for SLN biopsy after primary chemotherapy in patients who had proven axillary node metastases at presentation based on needle core biopsy were relatively high and a cause for clinical concern. However, more recent data suggest that SLN biopsy is as accurate when performed post- as pre-neochemotherapy and current practice incorporates both approaches.