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.