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Varying prevalence among ethnic groups of gene mutation that increases risk of breast cancer

CHICAGO – Among several U.S. racial/ethnic groups examined, Hispanic women were found to have the highest prevalence of the cancer-associated gene mutation BRCA1 at 3.5 percent, with Asian Americans having the lowest prevalence (0.5 percent), according to a study in the December 26 issue of JAMA.

Mutations in the tumor suppressor gene BRCA1 confer high risks of breast and ovarian cancer. Average cumulative risk by age 70 years has been estimated at 65 percent for breast cancer and 39 percent for ovarian cancer, according to background information in the article.

Although mutations in BRCA1 are rare, they are more frequently present in individuals with multiple relatives having breast or ovarian cancer, early-onset breast cancer, or of Ashkenazi Jewish ancestry. Information on the prevalence of BRCA1 mutation carriers in racial/ethnic minority populations is limited.

Esther M. John, Ph.D., of the Northern California Cancer Center, Fremont, Calif., and colleagues examined the prevalence of BRCA1 mutations in Hispanic, African American and Asian American female breast cancer patients compared with non-Hispanic white patients with and without Ashkenazi Jewish ancestry.

The patients, younger than 65 years at diagnosis, were enrolled at the Northern California site of the Breast Cancer Family Registry (n = 3,181) during the period 1996-2005.

In patients without reported Ashkenazi Jewish ancestry, estimated mutation prevalence was highest in Hispanic patients (3.5 percent), followed by non-Hispanic white patients (2.2 percent), African American patients (1.3 percent), and Asian American patients (0.5 percent).

Those with Ashkenazi Jewish ancestry had a prevalence of 8.3 percent. Within each racial/ethnic group, prevalence estimates decreased with age at diagnosis and were higher in patients who reported a family history of breast or ovarian cancer than in those who did not.

The prevalence of BRCA1 mutations was particularly high in African American patients diagnosed before age 35 years (16.7 percent), compared with young Hispanics (8.9 percent), non-white Hispanics without Ashkenazi Jewish ancestry (7.2 percent), and Asian Americans (2.4 percent).

“The present study included multiple racial/ethnic groups, therefore allowing direct comparison of carrier prevalence estimates. Since certain mutations may be unique to specific populations, the full spectrum of mutations needs to be determined.

Such information may facilitate mutation screening in a clinical setting and is needed to guide resource allocation for genetic testing, genetic counseling, and planning of preventive interventions in all population subgroups,” the authors conclude.

Editorial: Genetic Testing in Diverse Populations - Are Researchers Doing Enough to Get Out the Correct Message?

In an accompanying editorial, Dezheng Huo, M.D., Ph.D., and Olufunmilayo I. Olopade, M.D., of the University of Chicago, comment on the findings regarding genetic testing for BRCA1.

“As documented by John et al, more than half of BRCA1 mutation carriers would be detected in female patients with breast cancer whose cancers are likely to be hereditary based on age at diagnosis and family history. The differences in BRCA1 mutation prevalence across populations should be used to more accurately calculate the pretest probability of having a mutation, rather than as evidence against genetic testing in minority populations. While there has been great debate about the role of race/ethnicity in health research, clinicians interested in providing patients with personalized assessment of cancer risk must understand the contributions of BRCA1 and BRCA2 mutations in diverse populations, because potential modifying factors particular to patients’ race/ethnicity, family history, ancestral country of origin, and environmental factors may work in concert to influence outcomes.”