Neoadjuvant chemotherapy with trastuzumab in HER2-positive breast cancer: pathologic complete response rate, predictive and prognostic factors

Abstract The purpose of this study was to retrospectively review the pathologic complete response (pCR) rate from patients (n=86) withstage II and III HER2-positive breast cancer treated with neoadjuvant chemotherapy at our institution from 2008 to 2013 and todetermine possible predictive and prognostic factors. Immunohistochemistry for hormone receptors and Ki-67 was carried out.Clinical and pathological features were analyzed as predictive factors of response to therapy. For survival analysis, we usedKaplan-Meier curves to estimate 5-year survival rates and the log-rank test to compare the curves. The addition of trastuzumabto neoadjuvant chemotherapy significantly improved pCR rate from 4.8 to 46.8%, regardless of the number of preoperativetrastuzumab cycles (P=0.0012). Stage II patients achieved a higher response rate compared to stage III (P=0.03). The disease-free and overall survivals were not significantly different between the group of patients that received trastuzumab in theneoadjuvant setting (56.3 and 70% at 5 years, respectively) and the group that initiated it post-operatively (75.8 and 88.7% at5 years, respectively). Axillary pCR post neoadjuvant chemotherapy with trastuzumab was associated with reduced risk ofrecurrence (HR=0.34; P=0.03) and death (HR=0.21; P=0.02). In conclusion, we confirmed that trastuzumab improves pCRrates and verified that this improvement occurs even with less than four cycles of the drug. Hormone receptors and Ki-67expressions were not predictive of response in this subset of patients. Axillary pCR clearly denotes prognosis after neoadjuvanttarget therapy and should be considered to be a marker of resistance, providing an opportunity to investigate new strategies forHER2-positive treatment.Key words: Neoadjuvant chemotherapy; Trastuzumab; Pathologic complete response; Predictive factors of response;Prognosis