Cancer-free women (aged ≥18 years) with BRCA1 PV or BRCA2 PV, with no prior mastectomy, who underwent RRBO between January 1, 2000, and December 31, 2024, and who had at least 1 year of follow-up after RRBO were included.<h4>Exposures</h4>HRT use after RRBO.<h4>Main outcomes and measures</h4>First diagnosis or incidence of invasive BC. The gene discussed is BRCA1; the disease is breast cancer.