Histopathologic evidence of tumor regression in the axillary lymph nodes of patients treated with preoperative chemotherapy correlates with breast cancer outcome

Background: The benefits of primary tumor downstaging and assessment of chemoresponsiveness have resulted in expanded applications for induction chemotherapy. However, the pathologic evaluation and prognostic significance of response in preoperatively treated lymph nodes have not been defined. Methods: The axillary lymph nodes of 71 patients with locally advanced breast cancer treated with induction chemotherapy were evaluated for histological evidence of tumor regression as defined by the presence of nodal fibrosis, mucin pools, or aggregates of foamy histiocytes. Results: Complete pathologic response in the breast and axilla occurred in 10 patients (14%); 19 (26.8%) had evidence of tumor regression in 1 or more lymph nodes. Patients without nodal metastases and no evidence of tumor regression had the best outcome (median disease-free survival, 31.5 months; relapse rate, 27%). Patients with residual nodal metastases and no evidence of treatment effect had the worst outcome (median disease-free survival, 19.8 months; relapse rate, 55%). The median disease-free survival was 22.1 months, and the relapse rate was 32% for patients with histopathologic evidence of tumor regression in the axillary lymph nodes. Conclusions: Detection of treatment effect in axillary lymph nodes after induction chemotherapy identifies a subset of patients with an outcome intermediate between that of completely node-negative and node-positive patients. The axillary lymph nodes of patients receiving preoperative chemotherapy should be routinely analyzed for the presence of these features.