BRCA1 and breast cancer: On the other hand, in a 2012 study of 238 high-risk breast cancer patients in Korea (including 49 BRCA1/2 PV carriers), the proportional incidence of a family history of GC did not vary between patients without BRCA1/2 PVs and BRCA1/2 PV carriers (24.7% vs. 20.5%; RR 0.947, 95% CI 0.822–1.091) [51].