Survival of Breast-Conserving Surgery Plus Radiotherapy versus Total Mastectomy in Early Breast Cancer

Background: Breast-conserving surgery (BCS) has been reported to have better survival rates when compared with total mastectomy (TM) in early breast cancer. We evaluated the long-term outcomes of Korean women with early breast cancer who underwent either BCS plus radiotherapy (RT) or TM. Methods: In this population-based study, we evaluated 45,770 patients from the Korean Breast Cancer Registry (KBCR) who were diagnosed with early breast cancer, and divided them into the BCS + RT and TM groups. To minimize bias caused by factors other than the surgical method, we used exact match pairing of prognostic factors. We compared the 10-year overall survival (OS) and breast cancer-specific survival (BCSS) before and after exact matching. As the KBCR is a multicenter, online-based registry program, we used the Asan Medical Center (AMC) database, a single-center database, to validate the results from the KBCR database. Results: In both the KBCR and AMC cohorts, the BCS + RT group showed better OS and BCSS than the TM group, before and after exact matching. For the KBCR cohort after exact matching, the hazard ratios for OS and BCSS were 1.541 (95% confidence interval [CI] 1.392–1.707, p < 0.001) and 1.405 (95% CI 1.183–1.668, p < 0.001), respectively, favoring the BCS + RT group. For the AMC cohort after exact matching, the hazard ratios for OS and BCSS were 1.854 (95% CI 1.476–2.328, p < 0.001) and 1.807 (95% CI 1.186–2.752, p = 0.006), respectively. Conclusions: Our results suggest that BCS + RT is at least equivalent to TM in terms of OS and may affect treatment decisions in early breast cancer patients.