The Effect of Adjuvant Trastuzumab on Locoregional Recurrence of Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Treated with Mastectomy

Background Human epidermal growth factor receptor 2 (HER2) overexpression was associated with locoregional recurrence (LRR) in the preadjuvant trastuzumab era. This study aimed to examine the effect of trastuzumab on LRR in mastectomy patients and whether it varied with postmastectomy radiation (PMRT). Methods From the authors’ institutional database, 501 women with stages I–III HER2-positive breast cancer who underwent mastectomy from 1998 to 2007 were identified. A landmark analysis was performed to compare two cohorts: 170 women who received trastuzumab and 281 who did not. Kaplan–Meier methods were used to estimate locoregional recurrence-free survival (LRRFS). A propensity score analysis was used to balance the treatment groups with respect to multiple covariates. Analogous methods were used to study the effect of PMRT. Results The women in the trastuzumab group were more likely to be node positive and to receive systemic therapy or PMRT ( p