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.

Abstract

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 superior in pts with both ypT0 and ypTis/ypT1mic (no gross invasive residual BC) compared with those with gross residual disease (60.6 and 62.7 mo respectively vs. 51.6 mo, p=0.011 and 0.017). There was no difference in DFS between ypT0 and ypTis/ypT1mic pts (p=0.402). The rate of no gross invasive residual BC was significantly superior in pts with ER-PR- tumors compared with patients with ER+/PR+ tumors (69.9% vs. 56.7%, p=0.034). No gross invasive residual BC was associated with improved DFS in pts with HER2+ ER-/PR- (60.3 vs. 49.0 mo; p=0.005), as opposed to HER2+ ER+/PR+ tumors (61.0 vs. 51.6 mo; p=0.100). Multivariate analysis showed that tumor size (p=0.013) and no gross invasive residual BC (p=0.13) were associated with improved DFS in all subgroups. Conclusions: The absence of gross invasive residual BC was associated with improved DFS in pts with HER2+ BC treated with T-based neoadjuvant chemotherapy, particularly in those with HER2+ ER-/PR- BC. Our data suggest a comparable DFS in HER2+ BC patients with no gross invasive residual BC regardless of the presence or absence of both ypTis and ypT1mic disease after neoadjuvant treatment.