Benefit of adjuvant chemotherapy with or without trastuzumab in pT1ab node-negative human epidermal growth factor receptor 2-positive breast carcinomas: results of a national multi-institutional study

Purpose Benefit of adjuvant trastuzumab-based chemotherapy for node-positive and/or >1 cm human epidermal growth factor receptor 2-positive (HER2+) breast carcinomas has been clearly demonstrated in randomized clinical trials. Yet, evidence that adjuvant chemotherapy with or without trastuzumab is effective in pT1abN0 HER2+ tumors is still limited. The primary objective of this study was to investigate the impact of adjuvant chemotherapy ± trastuzumab on outcome in this subpopulation.