Postmastectomy radiation therapy in T3 node-negative breast cancer

Background In the absence of lymph node involvement, tumor size is arguably the most important prognostic factor for women with breast cancer. Radiation therapy use in the T3 node-negative population is controversial. We investigated the use of postmastectomy radiation therapy (PMRT) in women with T3 node-negative breast cancer. Methods A retrospective cohort study was conducted by identifying women with T3 node-negative breast cancer from the 1988-2009 Surveillance, Epidemiology and End Results database. Our primary outcome was breast cancer-specific survival. Survival curves were generated using the Kaplan-Meier method. Cox proportional hazard ratios (HRs) and propensity score analysis were used to evaluate the impact on survival. Results We identified 2874 patients with T3 node-negative breast cancer and 961 (33%) received PMRT and 1913 (67%) did not. Statistically significant differences were seen in adjuvant radiation therapy use based on patient age, marital status, tumor grade, tumor size, and receptor status (P < 0.05 for all). Overall survival was lower in the PMRT group in unadjusted analysis (crude HR, 0.718; 95% confidence interval [CI], 0.614-0.840); however, adjusted HRs demonstrated no difference in overall survival (adjusted HR, 0.898; 95% CI, 0.765-1.054). Unadjusted analysis of breast cancer-specific survival demonstrated no difference between those who received PMRT and those who did not (crude HR, 0.834; 95% CI, 0.682-1.021). Propensity score analysis demonstrated no difference in breast cancer-specific survival based on PMRT use (adjusted HR, 0.939; 95% CI, 0.762-1.157). Conclusions Analysis of the Surveillance, Epidemiology and End Results database suggests that receipt of PMRT is not clinically beneficial in T3 node-negative breast cancer.