BRCA1 and BRCA2 mutations are responsible for the majority of breast and ovarian cancers in families with high-risk profiles. Some 36 percent to 85 percent of women with the mutation will develop breast cancer, and of those that do, there is risk also of developing ovarian cancer.
Researchers have accumulated a wealth of knowledge about BRCA1 and BRCA2 in high-risk families, but know relatively little about the prevalence of the mutations in the general population, especially among black women and older women.
The authors looked at the prevalence of BRCA1 and BRCA2 mutations in 1,628 women with breast cancer and 674 women without breast cancer. The women, aged 35 to 64, were participants in the National Institute of Child Health and Human Development's Women's Contraceptive and Reproductive Experiences (CARE) Study, and were from the Seattle, Los Angeles, Atlanta, Detroit and Philadelphia metropolitan areas.
Among those with breast cancer, 2.4 percent and 2.3 percent carried mutations in the BRCA1 and BRCA2 genes respectively. About 2 percent of women who were aged 60 to 64 at the time of diagnosis were mutations carriers.
Among those without breast cancer, BRCA1 mutations were found in 0.04 percent, and BRCA2 mutations in 0.4 percent.
Overall, BRCA1 mutations were more common in white women (2.9 percent) vs. black women (1.4 percent) and in Jewish (10.2 percent) vs. non-Jewish (2 percent) women.
Mutations in BRCA2 were slightly more common in black women (2.6 percent) than in white women (2.1 percent).
This is one of the first studies to look at the prevalence of BRCA1 and BRCA2 mutations in black women. "The lack of research has led to the impression that it's more of a problem for Caucasian women," said lead investigator Kathleen E. Malone, of the Fred Hutchinson Cancer Research Center, in Seattle. "Our study shows that the overall frequency of mutations is generally similar across these two races, and so, at the very least, clinicians and women who are African-American should be thinking about this to the same extent as Caucasian women."
The researchers also looked at factors which predicted whether a woman carried one of the mutations. The strongest predictors of carrying a BRCA1 mutation were being diagnosed with breast cancer before the age of 45 or having a relative diagnosed before the age of 45, or ovarian cancer in a relative as well as having Jewish ancestry.
Early age at diagnosis in the patient or in relatives was a predictor of BRCA2 mutation status.
This information is critical for identifying which women might benefit from genetic testing.
"The study basically confirms that the No. 1 way to predict whether a person is going to have one of two genetic mutations is something really cheap: talk to the patient, ask them about their family history," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System, in Baton Rouge, La.
"Early age of onset of breast cancer and family history of ovarian cancer are two of the strongest predictors," he added.
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