Consistent with prior studies (13, 14, 25), a sample was classified as HRD for training purposes (i.e., ground truth) if it had an HRD score of at least 42 for breast cancer (5) or 63 for ovarian cancer (19) or if it harbored pathogenic germline variants, somatic mutations, or promoter methylation in BRCA1 or BRCA2. Here, BRCA1 is linked to breast cancer.