The Korean Hereditary Breast Cancer (KOHBRA) study was established to evaluate 
the prevalence and spectrum of BRCA1/2 mutations in Korean breast cancer 
patients at risk for hereditary breast and ovarian cancer. A total of 2953 
subjects (2403 index patients and 550 family members of affected carriers) from 
36 centers participated in this study between May 2007 and December 2013. All 
participants received genetic counseling and BRCA genetic testing. In total, 378 
mutation carriers among 2403 index patients were identified. The prevalence of 
BRCA mutations in specific subgroups was as follows: 22.3 % (274/1228) for 
breast cancer patients with a family history of breast/ovarian cancers, 8.8 % 
(39/441) for patients with early-onset (<35 years) breast cancer without a 
family history, 16.3 % (34/209) for patients with bilateral breast cancer, 4.8 % 
(1/21) for male patients with breast cancer, and 37.5 % (3/8) for patients with 
both breast and ovarian cancer. From an analysis of the mutation spectrum, 63 
BRCA1 and 90 BRCA2 different mutations, including 44 novel mutations, were 
identified. The c.7480 (p.Arg2494Ter) mutation in BRCA2 (10.1 %) was the most 
commonly identified in this cohort. The KOHBRA study is the largest cohort to 
identify BRCA mutation carriers in Asia. The results suggest that the prevalence 
of BRCA mutations in familial breast cancer patients is similar to that among 
Western cohorts. However, some single risk factors without family histories 
(early-onset breast cancer, male breast cancer, or multiple organ cancers) may 
limit the utility of BRCA gene testing in the Korean population.