Long-term follow-up after preoperative trastuzumab and chemotherapy for HER2-overexpressing breast cancer

Background Neoadjuvant chemotherapy and trastuzumab is an established treatment for locally advanced HER2-positive breast cancer, providing favorable rates of clinical response and pCR. Minimal data describe long-term outcomes after neoadjuvant HER2-directed therapy. This study aimed to explore long-term efficacy and toxicity after neoadjuvant trastuzumab and chemotherapy for HER2-positive breast cancer. Patients and Methods Eligible patients participated in 1 of 2 single-arm phase II neoadjuvant trials, receiving either paclitaxel/trastuzumab (TH) or vinorelbine/trastuzumab (NH) for stage II-III HER2-positive disease. Postoperative chemotherapy, with or without trastuzumab, was offered. Charts were reviewed to identify recurrence, death, and treatment-related toxicities. Association of long-term outcomes with baseline characteristics and pathological response to primary therapy was explored. Results Eighty patients were identified; 33 (41.3%) received TH and 47 (58.8%) received NH. Fourteen (17.5%) had pCR at surgery. Most (96.3%) received anthracycline-based adjuvant chemotherapy; 78.7% of NH patients also received adjuvant trastuzumab. At a median follow-up of 8.8 years, 23 (28.8%) patients have experienced recurrence, with 16 breast cancer-related deaths. Four-year RFS in patients with pCR was 92.9% (95% confidence interval [CI], 79.4%-100%) versus 72.4% without pCR (95% CI, 63.9%-82.1%). All initial symptomatic cardiotoxicity resolved during extended follow-up. New symptomatic cardiotoxicity in long-term follow-up was rare, primarily occurring in patients requiring retreatment with a cardiotoxic agent. Conclusion Neoadjuvant chemotherapy and trastuzumab for HER2-positive breast cancer resulted in favorable long-term survival with minimal late toxicity. Trends in this data set suggest an association between pCR and improved long-term RFS. Retreatment with cardiotoxic agents might increase risk of late cardiotoxicity.