Conversion rate from mastectomy to breast conservation after neoadjuvant dual target therapy for HER2-positive breast cancer in the Asian population

Abstract

Dual HER2 blockade with transtuzumab and pertuzumab is known to be associated with improved oncologic outcome, however, its evidence on the impact of surgical decision remains limited. This study aims to evaluate the efficacy of dual HER2 blockade, when compared to single blockade, in improving breast conservation rate in an Asian cohort. Retrospective study was performed on a prospectively-maintained database in our tertiary academic-based hospital, including patients with non-metastatic, HER2-positive breast cancer receiving neoadjuvant systemic therapy (NST) between January 2014 and December 2018. 142 patients were analyzed: 75 received Herceptin (H)-based NST and 67 received H + Pertuzumab (P)-based NST. Before NST, 65 patients (45.8%) were eligible for breast conserving therapy (BCT); and this increased to 103 (72.5%) after NST. Thirty-seven out of 75 patients (49.3%) who were deemed not BCT candidate converted to BCT-eligible after NST. More than half of the patients who were BCT-eligible opted for mastectomy. PH-based comparing to H-based NST did not differ significantly in BCT rate (35.5% vs 32.0%, P = 0.72); but there was a trend of increase in conversion to BCT-eligible rate (43.9-52.8%), reducing tumor diameter (40.2-53.1% reduction) and volume (69.5-80.0% reduction). The conversion rate from mastectomy to BCT-eligible was more than 50% after dual target therapy, which was slightly higher than single target agent. However the actual BCT rate was not significantly increased, and more than half of the BCT-eligible patients opted for mastectomy.