Racial differences in the incidence of BRCA1 and BRCA2 mutations in a cohort of early onset breast cancer patients: African American compared to white women

Purpose: To evaluate the frequency and distribution of BRCA1 and BRCA2 mutations in a cohort of young women with breast cancer and to compare the distribution of mutations as a function of race. Methods: After IRB approved informed consent, 170 white women and 30 African American women with known breast cancer diagnosed at a young age ( 45 years or less) underwent complete sequencing of the BRCA1 and BRCA2 genes. Each cohort represented approximately 40% of women of the same ethnic background aged 45 years or younger in a breast cancer database. Results: Of the 200 patients tested, 131 (65%) had wild type mutations, 34 (17%) had deleterious mutations, and 35 (18%) had variants of uncertain significance. There were no significant differences between the white and African American cohorts regarding the percentage of deleterious mutations ( 17% v 17%). However, most African American patients had mutations in BRCA2 (4/5, 80%), while most mutations in the white cohort were in BRCA1 (20/29, 69%). In addition, 46% of the African American women had variants of uncertain significance, compared to only 12% of the white cohort. Conclusions: Young African American women with breast cancer have a similar frequency of deleterious mutations as white women, but have a significantly higher frequency of variants of uncertain significance. Review of these variants revealed that the majority were unlikely to be associated with disease risk or were likely to be polymorphisms. The implications for genetic testing and counselling in young women with breast cancer are discussed.