When applied in a cohort of 560 breast cancer patients with 22 germline BRCA1/2 mutation carriers as the positive control, HRDetect detected additional 33 tumors with a germline BRCA1/2 mutation, 22 tumors with a somatic BRCA1/2 mutation, and 47 samples with high HRDetect scores (> 0.7) without harboring BRCA1/2 mutations, increasing the predicted BRCA1/2-deficiency rate to 22% (124/560) with the sensitivity of 98.7%. This evidence concerns the gene BRCA1 and breast cancer.