Weekly paclitaxel plus carboplatin with or without trastuzumab as neoadjuvant chemotherapy for HER2-positive breast cancer: loss of HER2 amplification and its impact on response and prognosis

Purpose Neoadjuvant chemotherapy (NCT) plus anti-HER2 agents are the standard of care for locally advanced HER2-positive breast cancer. The aim of this study was to evaluate the prevalence and prognostic impact of HER2 loss in patients with HER2-positive disease treated with neoadjuvant therapy with or without trastuzumab. Methods 549 consecutive HER2-positive patients were included in this study. 379 patients were treated with paclitaxel, carboplatin, and trastuzumab (PCH cohort) and 170 were treated with paclitaxel and carboplatin only (PC cohort). Conversion of biomarkers before and after NCT was evaluated via immunohistochemistry (IHC) test. Cox regression model was used to investigate prognostic markers to relapse-free survival (RFS). Results 50.9% patients were considered as pCR responder in PCH cohort, whereas only 25.9% of patients experienced pCR in PC cohort ( P