Breast Cancer, Blacks: New Gene Clues

Dec. 26, 2007 -- African-American women diagnosed with breast cancer in their mid-30s or younger appear to be more likely than most other women to have a genetic predisposition for the disease, new research suggests.

The study, published today in The Journal of the American Medical Association, is one of the first to examine the prevalence of mutations in the tumor suppressor gene BRCA1 by ethnic group in breast cancer patients with and without a family history of breast cancer.

According to one estimate, nearly two out of three women who have the BRCA1 mutations are likely to develop breast cancer by age 70.

While African-American women as a group had a lower prevalence of BRCA1 mutations than most white and Hispanic women in the study, African-American women diagnosed with breast cancer before age 35 were roughly twice as likely to carry the mutations.

If confirmed in larger studies, this finding could help explain why African-Americans tend to develop more aggressive and deadly breast cancers than other racial groups, says researcher Esther M. John, PhD, of the Northern California Cancer Center.

"For whatever reason, African-American women are less likely to be tested [for BRCA mutations] than white women," John tells WebMD. "One message to clinicians might be that they should probably be tested more often."

BRCA Mutations by Ethnic Group

The study included female breast cancer patients -- younger than age 65 at diagnosis -- enrolled in a California breast cancer registry between 1996 and 2005.

Researchers confirmed a high prevalence of BRCA1 mutations among women of Ashkenazi Jewish ancestry, with 8.3% of these patients carrying the mutations compared to 3.5% of Hispanic women, 2.2% of non-Hispanic white women, 1.3% of African-American women, and 0.5% of Asian-American women.

Not surprisingly, BRCA1 mutations were more common in women with a family history of breast or ovarian cancer and less common in breast cancer patients diagnosed later in life.

Roughly 17% of African-American patients diagnosed with breast cancer prior to age 35 carried a BRCA1 mutation, compared to 8.9% of Hispanic patients, 7.2% of non-white Hispanics without Ashkenazi Jewish ancestry, and 2.4% of Asian-American patients.

Larger studies are needed to confirm the findings, John says, because of the small number of young breast cancer patients enrolled in the study. Just 30 of the 341 African-American study participants were younger than 35, and five of them tested positive for BRCA1 mutations.

Refining BRCA Testing

John and colleagues conclude that a better understanding of the expression of BRCA mutations among different racial and ethnic groups will help doctors better identify women who should be screened.

In an accompanying editorial, Dezheng Huo, MD, PhD, and Olufunmilayo Olopade, MD, of the University of Chicago call the study by John and colleagues "a good starting point for narrowing the knowledge gap in characterizing the BRCA1 gene."

Olopade tells WebMD that minority and other medically underserved women undergo genetic testing for BRCA mutations at a much lower rate than white women.

She and Huo write that it is important "to design and evaluate interventions for improving genetic testing uptake in underserved populations, so that genetic testing can achieve full potential as a tool for effective cancer control and prevention."