Bilateral Prophylactic Mastectomy Reduces Breast Cancer Risk in <i>BRCA1</i> and <i>BRCA2</i> Mutation Carriers: The PROSE Study Group

TLDR

Data on the efficacy of bilateral prophylactic mastectomy for breast cancer risk reduction in women with BRCA1 and BRCA2 mutations are limited, despite its clinical use. The study aimed to estimate the degree of breast cancer risk reduction following bilateral prophylactic mastectomy in BRCA1/2 mutation carriers. A prospective cohort of 483 BRCA1/2 mutation carriers, including 105 who underwent bilateral prophylactic mastectomy and 378 matched controls without the surgery, was followed for a mean of 6.4 years, with analyses adjusted for ovarian hormone exposure. Bilateral prophylactic mastectomy reduced breast cancer risk by about 90% overall, with a 95% reduction in women who also had oophorectomy and a 90% reduction in those with intact ovaries.

Abstract

Data on the efficacy of bilateral prophylactic mastectomy for breast cancer risk reduction in women with BRCA1 and BRCA2 (BRCA1/2) mutations are limited, despite the clinical use of this risk-management strategy. Thus, we estimated the degree of breast cancer risk reduction after surgery in women who carry these mutations.Four hundred eighty-three women with disease-associated germline BRCA1/2 mutations were studied for the occurrence of breast cancer. Cases were mutation carriers who underwent bilateral prophylactic mastectomy and who were followed prospectively from the time of their center ascertainment and their surgery, with analyses performed for both follow-up periods. Controls were BRCA1/2 mutation carriers with no history of bilateral prophylactic mastectomy matched to cases on gene, center, and year of birth. Both cases and controls were excluded for previous or concurrent diagnosis of breast cancer. Analyses were adjusted for duration of endogenous ovarian hormone exposure, including age at bilateral prophylactic oophorectomy if applicable.Breast cancer was diagnosed in two (1.9%) of 105 women who had bilateral prophylactic mastectomy and in 184 (48.7%) of 378 matched controls who did not have the procedure, with a mean follow-up of 6.4 years. Bilateral prophylactic mastectomy reduced the risk of breast cancer by approximately 95% in women with prior or concurrent bilateral prophylactic oophorectomy and by approximately 90% in women with intact ovaries.Bilateral prophylactic mastectomy reduces the risk of breast cancer in women with BRCA1/2 mutations by approximately 90%.