Outcomes of Breast-Conserving Surgery Plus Radiation vs Mastectomy for All Subtypes of Early-Stage Breast Cancer: Analysis of More Than 200,000 Women

Recent large retrospective studies suggest that breast-conserving therapy (BCT) plus radiation yielded better outcomes than mastectomy (MST) for women with early-stage breast cancer (ESBC). Whether this is applicable to the different subtypes is unknown. We hypothesize that BCT yielded better outcomes than MST, regardless of subtypes of ESBC.Data on women diagnosed with first primary stage I to II breast cancer between 2010 and 2017 who underwent either BCT or MST were from the population-based 18 Surveillance, Epidemiology, and End Results cancer registries. The Kaplan-Meier method was used to estimate unadjusted 5-year overall survival and cause-specific survival. Univariable and multivariable Cox proportional regression models were used to determine the impact of surgical approaches on the hazard ratios adjusted for relevant demographic and clinical variables for molecular subtype (luminal A, luminal B, triple-negative, and HER2 enriched).Of the 214,128 patients with breast cancer, 41.6% received MST. For the different subtypes, BCT yielded better 5-year overall survival and cause-specific survival than MST. After adjusting for demographic and clinical factors, the risk of overall survival and cause-specific survival was still statistically significantly higher among MST recipients than BCT recipients for all subtypes.BCT yielded better survival rates than mastectomy for women with all subtypes of ESBC. The role of mastectomy for women with ESBC should be reassessed in future clinical trials.