In this cohort study of 575 patients using propensity score matching, among patients with breast cancer with BRCA1 or BRCA2 pathogenic variants, there was no significant difference in oncologic outcomes such as locoregional recurrence, distant recurrence, and overall survival between BCT group and mastectomy group during a median follow-up of 8.3 years. The gene discussed is BRCA1; the disease is breast cancer.