Breast cancer risk in BRCA mutation carriers after diagnosis of epithelial ovarian cancer is lower than in carriers without ovarian cancer

OBJECTIVE: Evaluate the incidence and characteristics of breast cancers (BC) diagnosed following an epithelial ovarian cancer (EOC) diagnosis in women with pathogenic BRCA mutations. METHODS: Retrospective cohort study of all women in an integrated healthcare system with BRCA mutations diagnosed with EOC from 1/1/1997–12/31/2018. Primary outcome was rate of subsequent BC diagnosis. Secondary outcomes included risk factors associated with development of BC, median time to detection following EOC, and method of detection. RESULTS: There were 284 women with BRCA-associated EOC identified. Fifty-two women had risk-reducing mastectomy and were excluded. Of the 232 eligible women with a median follow-up of 5.6 years, 33 (14%) women were diagnosed with BC following EOC: 27 (11%) new cases and 6 (3%) recurrences. Twelve (36%) cases of BC were detected on screening mammogram, 4 (12%) on screening MRI, and 9 (27%) on work-up after presenting with a palpable lump. Twenty-nine (87%) were early stage (0-II) disease. Median interval from EOC to BC diagnosis was 80 months (IQR 32, 134) for new and 63 months (IQR 21, 94) for recurrent BCs. There was one death from breast cancer while 12 women died of ovarian cancer. CONCLUSIONS: Most BC following BRCA-associated EOC is early stage and not associated with mortality. Given BC rate similar to general population and median diagnosis at 6.6 years following ovarian cancer, increased BC screening may not be warranted in the early years after EOC diagnosis.