Breast cancer after ovarian cancer in BRCA1 and BRCA2 pathogenic variant heterozygotes: Lower rates for 5 years post chemotherapy

Purpose: The identi fi cation of germline BRCA1 / BRCA2 pathogenic variants (PV) infer high remaining lifetime breast/ovarian cancer risks, but there is paucity of studies assessing breast cancer risk after ovarian cancer diagnosis. Methods: We reviewed the history of breast cancer in 895 PV heterozygotes ( BRCA1 = 541). Cumulative annual breast cancer incidence was assessed at 2, 5, 10, and > 10 years after ovarian cancer diagnosis date. Results: Breast cancer annual rates were evaluated in 701 assessable women with no breast cancer at ovarian diagnosis ( BRCA1 = 425). Incidence was lower at 2 years (1.18%) and 2 to 5 years (1.13%) but rose thereafter for BRCA1 with incidence post 10 years in excess of 4% annually. Breast cancer pathology in BRCA1 PV heterozygotes showed less high-grade triplenegative breast cancer and more lower-grade hormone-receptor-positive cancer than women with no prior ovarian cancer. In the prospective cohort from ovarian cancer diagnosis, < 4% of all deaths were caused by breast cancer, although 50% of deaths in women with breast cancer after ovarian cancer diagnosis were due to breast cancer. Conclusion: Women can be reassured that incidence of breast cancer after ovarian cancer diagnosis is relatively low. It appears likely that this effect is due to platinum-based chemotherapy. Nonetheless women need to be aware that incidence increases thereafter, especially after 10 years. (c) 2024 The Authors. Published by Elsevier Inc. on behalf of American College of Medical Genetics and Genomics. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).