Pathologic response and disease-free survival (DFS) after neoadjuvant trastuzumab (T) for HER2+ breast cancer (BC): Results from the National Cancer Institute (NCI) of Mexico.

e11533 Background: The most accurate definition of pathologic complete response (pCR) in HER2+ BC patients (pts) receiving T-based neoadjuvant chemotherapy associated with improved DFS is controversial, particularly regarding the role of residual ductal carcinoma in situ (ypTis) and focal invasive residuals (ypT1mic). The effect of pCR on DFS in various subgroups of HER2+ BC is also uncertain. Methods: Pts with localized HER2+ BC that received T-based neoadjuvant chemotherapy at NCI between January 2007 and May 2012 were identified. We conducted an exploratory analysis of DFS in pts according to their tumor response. DFS curves were derived from Kaplan-Meier estimates and compared by log-rank test. Multivariate analysis was performed using Cox’s regression model. Results: 243 pts were included for analysis. Median follow-up was 39 months (mo). 49% of pts had no invasive and no in situ residuals at surgery (ypT0), 14.4% had ypTis/ypT1mic residuals and 36.6% had gross residual BC. DFS was significantly supe...