In a study, of more than 2,300 African-American and Caucasian women with and without breast cancer, the researchers found that among breast-cancer cases overall, 2.4% and 2.3% carried mutations in BRCA1 and BRCA2, respectively.
According to the researchers, BRCA1 mutations were significantly more common in white (2.9%) versus black (1.4%) cases and in Jewish (10.2%) versus non-Jewish (2%) cases. BRCA2 mutations were slightly more common in black (2.6%) versus white (2.1%) cases.
The researchers also examined predictors of carrying a mutation in either gene. The strongest and most significant predictors of carrying a BRCA1 mutation were diagnosis before age 45 in the patient or in a relative, ovarian cancer in a relative and Jewish ancestry. Predictors of BRCA2 mutation status included early age at diagnosis in the patient herself or in her relatives.
“While the primary thrust of this research was to identify predictors of carrying the high-risk mutations and to clarify mutation prevalence in understudied groups, the relatively small proportion of cases found to carry a mutation serves as a continued reminder that the majority of women with breast cancer, even those with a positive family history, do not carry mutations in these genes,” according to lead investigator Dr Kathleen Malone, a member of the Hutchinson Center’s Public Health Sciences Division.