Effect of hormone receptor status and local treatment on overall survival for early-stage breast cancer.

60 Background: Mastectomy and breast conserving therapy (BCT) have been established as interventions with equivalent survival for early stage breast cancer. However, trials comparing these approaches pre-date the understanding of breast cancer heterogeneity. We hypothesized that if heterogeneity is considered, the surgical approach may impact survival. Methods: Using the National Cancer Database (NCDB) from 2004 to 2005, we evaluated the overall survival (OS) of women with Stage I breast cancer who underwent mastectomy, BCT (surgery with radiation), or breast conserving surgery (BCS, surgery without radiation). Since only ER and PR data were available, we categorized tumors as ER and/or PR positive (HR+) or ER and PR negative (HR-). We performed propensity score-matched analysis using the covariates associated with the choice of surgical therapy. We used the Cox proportional hazards model for analyses of OS in pre-matched and matched cohorts. Double robust estimation under the Cox model was used in the an...