Margaret M Kozak, Clare E Jacobson, Rie von Eyben, Erqi L Pollom, Melinda Telli, Kathleen C Horst

Purpose: We sought to evaluate whether pathologic nodal response was predictive of outcomes in women aged ≤40 years with breast cancer treated with neoadjuvant chemotherapy (NAC). Methods: A total of 220 patients treated with NAC between 1991 and 2015 were retrospectively reviewed. Pathologic complete response (pCR) was defined as no evidence of residual invasive tumor in the breast and lymph nodes (LNs) (ypT0/Tis ypN0); partial response if there was no tumor in the LNs but residual tumor in the breast (ypT+ ypN0) or residual tumor in the LNs (ypT0/Tis ypN+); and limited response if there was residual tumor in both the breast and the LNs (ypT+ ypN+). Kaplan-Meier and Cox proportional hazards analyses were performed to identify factors predictive for overall survival (OS). Results: A total of 155 patients were included. Following NAC, 39 patients (25.2%) achieved pCR, 57 (36.8%) achieved a partial response (either ypT+ ypN0 or ypT0/Tis ypN+), and 59 (38.1%) had a limited response. A total of 22 patients (14.2%) experienced local failure, 20 (12.9%) experienced regional failure, and 59 (38.1%) experienced distant failure. Median OS for patients who achieved pCR was not reached, and was significantly worse for patients who had residual disease in the breast and/or LNs (P<.001). No difference in OS was seen among patients who had residual disease in the breast alone versus those who remained LN-positive (97 vs 83 months, respectively; P=.25). Subset analysis did not reveal differences in OS based on year of treatment or cN1 disease at the time of initial diagnosis. Conclusions: Women aged ≤40 years who achieved pCR had excellent outcomes; however, those who achieved a pathologic response in the LNs but had residual disease in the breast continued to have outcomes similar to those who remained LN-positive.