In 219 (82.0%) BRCA1/2 carriers without prior clinical BRCA1/2 testing compared with controls, the OR for personal history of any HBOC syndrome–associated cancer was 2.32 (95% CI, 1.63-3.29; P < .001), indicating significantly increased cancer risk associated with the BRCA1/2 carriers ascertained in this fashion. Here, BRCA1 is linked to cancer.