Abstract 2300: Deleterious germline mutations in the BRCA1 gene are associated with increased risk for cancers of the female reproductive system other than breast and ovarian as well as other cancers

Introduction: Mutations within the BRCA1 gene have been linked to up to an 80% lifetime risk of breast cancer as well as increased risk for ovarian, pancreatic and melanoma cancers. In this study we examined families with known germline mutations in BRCA1 after long-term follow-up to determine whether carriers experience higher rates of other cancers that have not yet been associated with germline mutations in the BRCA1 gene. Methods: We studied 127 Hereditary Breast and Ovarian Cancer (HBOC) syndrome families (N = 23,078 individuals who have been followed at Creighton University) in which a causal mutation in the BRCA1 gene was identified. We performed survival analysis and a mixed effects cox regression with age at follow-up or cancer event as our time variable and presence or absence of BRCA1-related or other cancers (separate analyses) as our indicator variable. Results: The survival curves showed a significant age effect with carriers having a younger age at cancer onset for BRCA1-related (as expected) as well as other cancers than that of non-carriers. The cox regression models were also highly significant (P = 1.77E-37 and P = 1.04E-07 for the BRCA1-related and other cancers, respectively). Of the cancers with enough samples to do stratified analyses, uterine, skin, lymphoma and colon cancers occurred at higher rates and at earlier ages in mutation carriers. Conclusions: These analyses support the hypothesis that the BRCA1 mutations carriers of HBOC syndrome have increased risk for early onset of several additional cancer types, especially cancers that arise in estrogen-influenced tissues. Citation Format: Candace Middlebrooks, Kenzhane Pantin, Mark Stacey, Carrie Snyder, Murray J. Casey, Trudy Shaw, Joan E. Bailey-Wilson, Henry T. Lynch. Deleterious germline mutations in the BRCA1 gene are associated with increased risk for cancers of the female reproductive system other than breast and ovarian as well as other cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2300.