BRCA1 and cancer: Prostate cancer (PCa) exhibits marked familial aggregation and has one of the highest heritabilities of any common cancer.1-4 This is explained in part by rare pathogenic variants (PVs) in BRCA2, HOXB13, and possibly BRCA1, which are associated with moderate-to-high PCa risks,5-14 together with several hundred commoner variants conferring lower risks, identified through genome-wide association studies.15-18