Incidence of Peritoneal Cancer Following Oophorectomy among BRCA1 and BRCA2 Mutation Carriers

Background To estimate the incidence of primary peritoneal cancer following preventive bilateral oophorectomy in women with a BRCA1 or BRCA2 mutation. Methods A total of 6,310 women with a BRCA1 or BRCA2 mutation who underwent a preventive bilateral oophorectomy were followed for a mean of 7.8 years from oophorectomy. The 20-year cumulative incidence of peritoneal cancer post-oophorectomy was estimated using the Kaplan-Meier method. A left-truncated Cox proportional hazard analysis was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CI) associated with the age at oophorectomy, year of oophorectomy, and family history of ovarian cancer as well as hormonal and reproductive risk factors. Results Fifty-five women developed primary peritoneal cancer (n = 45 in BRCA1, 8 in BRCA2, and 2 in women with a mutation in both genes). Their mean age at oophorectomy was 48.9 years. The annual risk of peritoneal cancer was 0.14% for women with a BRCA1 mutation and was 0.06% for women with a BRCA2 mutation. The 20-year cumulative risk of peritoneal cancer from the date of oophorectomy was 2.7% for BRCA1 carriers and was 0.9% for BRCA2 mutation carriers. There were no peritoneal cancers in BRCA1 carriers who had the operation before age 35 or in BRCA2 carriers who had the operation before age 45. Conclusions For BRCA1 mutation carriers, the annual risk of peritoneal cancer for 20 years post-oophorectomy is 0.14% per year. The risk is lower for BRCA2 carriers (0.06% per year).