Homologous recombination deficiency in ovarian high-grade serous carcinoma by self-reported race

BackgroundApproximately half of ovarian high-grade serous carcinomas (HGSC) have homologous recombination deficiency (HRD). However, HRD is not well-characterized in Black individuals. ObjectiveTo characterize HGSC HRD by self-reported race and evaluate whether differences in HRD are associated with ovarian cancer mortality. Study populationCohort study using data collected from two population-based case-control studies of ovarian cancer. Cases were selected based on self-reported race (178 Black, 123 White) and pathologically-confirmed HGSC. ExposuresHRD features identified using matched tumor-normal whole-exome DNA sequencing and categorized as germline or somatic variants in homologous recombination pathway genes, or the SBS3 HRD-associated signature. OutcomesMedian difference and 95% confidence intervals (CI) for age at diagnosis and tumor mutation burden, and age and stage-adjusted hazard ratios (HR) and 95%CIs for survival, comparing individuals with an HRD feature to those without, separately by self-reported race. ResultsMore of the germline and somatic variants detected among Black individuals compared with White individuals were unannotated or variants of uncertain significance (VUS; germline 65% versus 45%; somatic 62% versus 50%, respectively). While the prevalences of many HRD features were similar between Black individuals and White individuals, Black individuals had a higher prevalence of the HRD signature identified using de novo mutational signature analysis (40% versus 29%) and germline BRCA2 variants (8% versus 2%) compared with White individuals. We observed that among Black individuals, BRCA2 variants were associated with better survival (somatic HR=0.23, 95%CI 0.07-0.76; germline HR=0.48, 95%CI 0.22-1.03), while germline BRCA1 variants were associated with worse survival (HR=2.11, 95%CI 1.14-3.88). When we restricted to VUS and unannotated variants, we observed similar associations with survival for BRCA2 among Black individuals (somatic HR=0.18, 95%CI 0.04-0.75; germline HR=0.40, 95%CI 0.15-1.09). Conclusions and RelevanceHRD testing informs precision-based medicine approaches that improve outcomes, but a higher proportion of VUS among Black individuals may complicate referral for such care. Our findings emphasize the importance of recruiting diverse individuals in genomics research and better characterizing VUS.