The Korean Hereditary Breast Cancer (KOHBRA) study: protocols and interim report.

Aims: The primary aims of the Korean Hereditary Breast Cancer (KOHBRA) study are to estimate the prevalence of BRCA1/2 mutations and ovarian cancer among a high-risk group of patients with hereditary breast cancer and their families.

Materials And Methods: The KOHBRA study is a prospective multicentre cohort identifying cases and their families. Between May 2007 and May 2010, the KOHBRA study enrolled up to 2000 subjects. All participants received genetic counselling and BRCA genetic testing; the clinical information and blood samples for blood banking were collected. An interim analysis of the prevalence of BRCA1/2 mutations and ovarian cancer in Korean subjects was determined from the initial 975 patients who presented to 33 centres.

Results: By April 2009, a total of 167 mutation carriers among 853 probands were identified. The prevalence of the BRCA mutation was as follows: 24.8% (106/428) for breast cancer patients with a family history of breast/ovarian cancers; 11.3% (24/212) for patients with early-onset (<35 years) breast cancer without a family history; 22.1% (15/68) for patients with bilateral breast cancer; male breast cancer in 8.3% (1/12); and 33.4% (1/3) for patients with breast and ovarian cancer.

Conclusions: The results of this study suggest that the prevalence of BRCA mutations in Korean subjects is similar to the prevalence reported among Western cohorts. However, weak family history and non-familial early-onset of breast cancer were significant factors associated with carrying the BRCA mutation in Korean breast cancer patients. Completion of the KOHBRA study is needed to confirm these findings.