Varying prevalence among ethnic groups of gene mutation that increases risk of breast cancer
CHICAGO â€“ 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).
â€œThe 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,â€ the authors conclude.