Utilization and impact of a postmastectomy radiation boost for invasive breast cancer.

Abstract

Additional radiation following postmastectomy radiation (PMRT) has an undefined benefit. We investigate those likely to be selected for a chest wall boost (CWB) and its effect on breast cancer survival (BCS) and overall survival (OS). A total of 4747 women diagnosed from 2005 to 2009 were treated with PMRT identified from the California Cancer Registry (CCR); 2686 (57%) received a CWB. Univariate and multivariate analyses compared those receiving and not receiving a CWB for BCS and OS. With a median follow-up of 43.6 months, patients likely to receive a CWB were stage III (P ≤ .001), grade 3/4 (P = .03), positive nodes (P = .04), HER 2+ (P =.02). CWB was not related to BCS in the univariate (hazard ratio [HR], 1.00; 95% confidence interval [CI], 0.82-1.21), multivariate (HR, 1.04; 95% CI, 0.86 -1.26) analyses, and was not related OS for the univariate (HR, 0.92; 95% CI, 0.78-1.10), multivariate (HR, 0.95; 95% CI, 0.80-1.13) analyses. However, in multivariate analysis, patients not receiving chemotherapy who had a CWB had better BCS (HR, 1.77; 95% CI, 1.11-2.83). The majority of patients were treated with a CWB. We found no difference in BCS or OS with the addition of a CWB.