BRCA1 and breast cancer: Similarly, in a 2019 study in Korea among first- and second-degree relatives of high risk breast cancer patients (n = 2555, including 377 BRCA1/2 PV carriers), the proportional incidence of a family history of GC was higher among BRCA1/2 PV carriers compared to patients without a BRCA1/2 PV (13.8% vs. 7.4%; OR 1.666, 95% CI 1.183–2.345) [50].