HRDetect in Tubo-ovarian Carcinoma: Stratification and Therapeutic Implications.

To evaluate HRDetect, a mutational-signature-based algorithm, for prognostic utility in tubo-ovarian carcinoma (OC), and to determine if whole-genome sequencing (WGS) with rearrangement signature (RS) analysis can refine genomic classification beyond the traditional homologous recombination deficient (HRD) versus proficient (HRP) framework. WGS was performed on matched tumor-normal pairs from 185 patients with advanced-stage OC from the University of Washington (UW) cohort. HRDetect scores were calculated using substitution signatures, rearrangement signatures, microhomology-mediated deletions, and global loss of heterozygosity. An independent validation cohort (ARIEL2, n = 77) of platinum-sensitive OC treated with rucaparib, was analyzed to correlate HRDetect with PARP inhibitor (PARPi) response. RS analysis and unsupervised hierarchical clustering were employed to delineate genomic subgroups. In the UW cohort, 51.4% of cases were classified as HRDetect-high and had significantly prolonged median overall survival versus others (6.2 vs 4.1 years; HR=0.6; 95% CI=0.41-0.87; p=0.007). 48.4% of HRDetect-high tumors harbored BRCA1/2 mutations or BRCA1 promoter methylation, while 22.1% lacked BRCA1/2 alterations. A substantial fraction (23.2%) fell into an HRDetect-intermediate category, highlighting greater genomic heterogeneity than currently appreciated. RS profiling uncovered eleven genomic clusters, with specific RS profiles (RS1, RS14, RS18) correlating with poor survival. In ARIEL2, HRDetect-high tumors showed better PARPi responses, with improved progression-free survival (11.1 vs 7.1 months; HR=0.44; 95% CI=0.26-0.74; p=0.03) and response rates (54% vs 22.5%). HRDetect predicts survival and sensitivity to PARPi in OC. Combined with RS-based clustering, it reveals unappreciated genomic heterogeneity, and supports a nuanced stratification framework to improve precision oncology in OC.