Incidence of endometrial cancer in BRCA mutation carriers

Objective: Whether or not women who harbor a germline pathogenic variant (‘mutation’) in the BRCA1 or BRCA2 genes are at elevated risk of developing endometrial cancer is yet to be determined. Methods: We conducted a prospective analysis of 4959 BRCA mutation carriers with no prior history of cancer (except for breast or melanoma) and an intact uterus. Results: After a mean of 6.7 years of follow-up there were 38 incident cases of endometrial cancer diagnosed; 30 among BRCA1 carriers and eight among BRCA2 carriers. The mean age at diagnosis was 58.4 years (range 46.8–76.1). The majority were of the endometrioid subtype (n = 16), followed by mixed endometroid and serous (n = 4), serous (n = 3) or clear cell (n = 1) (missing = 13). The cumulative incidence from age 40 to age 70 was 3.4% for BRCA1 carriers and was 1.6% for BRCA2 mutation carriers. Prior tamoxifen use was associated with a significant two–fold increased risk (HR = 2.24; 95% CI 1.10–4.55). There was no significant association between exogenous hormone use, oophorectomy, smoking or BMI at age 40 and risk (P ≥ 0.32). Conclusions: Compared to the general population, we observed higher rates of endometrial cancer among young BRCA1 mutation carriers; however, lifetime risks were similar. Women with prior tamoxifen exposure were at a significantly increased risk. These findings were based. on a small number of incident cases and require confirmation with additional follow-up of our aging cohort.