BRCA mutations among Asian-Americans may be more common than predicted

In this New Digest:

• Summary of a study published online September 8, 2008 in the Journal of Clinical Oncology, showing that computer models commonly used to decide who might benefit most from genetic testing under predicted the number of Asian-American women with BRCA1 or BRCA2 mutations.
• Quote for attribution from Ramona Swaby, MD, American Society of Clinical Oncology breast cancer expert
• Links to additional information from ASCO's Cancer.Net

Study suggests more Asian American women may need to be tested for BRCA mutations

Researchers from the U.S. and Canada found that two computer models widely used to determine who should undergo genetic testing for BRCA mutations under predicted mutation frequency in Asian-American women by 50 percent. Mutations in the BRCA1 and BRCA2 genes significantly increase the risk of breast and ovarian cancers, and women who learn they have these mutations are encouraged to seek more frequent cancer screening or may undertake other measures to reduce their cancer risk, such as preventive mastectomy or removal of the ovaries.

The incidence of breast cancer among Asians is generally lower than among Caucasians. However, breast cancer rates are increasing in China, Korea and other Asian countries and among Asian immigrants to the United States, which has led to increasing demand for BRCA1/2 mutation testing in this population.

"Our findings indicate that Asian-American women with BRCA mutations may not be referred for genetic testing as often as they should be," said lead author Allison Kurian, MD, MSc, assistant professor of medicine and of health research and policy at Stanford University School of Medicine. "While women of Asian descent have, in the past, been at lower risk for breast and ovarian cancers compared with other races, these findings will be important for physicians to keep in mind when assessing whether their Asian-American patients are candidates for BRCA mutation testing."

The models, called BRCAPRO and Myriad II, are commonly used to determine which patients inquiring about genetic consultation would benefit most from genetic testing for BRCA mutations. These models were initially created using data on BRCA mutations in Caucasians, and some studies have shown these models accurately predicted gene mutation risk in other minority groups, including African-Americans and Hispanics.

For this study, researchers compared the results of the BRCAPRO and Myriad II computer prediction models with the findings of genetic testing in 200 Asian-Americans and 200 matched non-Jewish Caucasians. (Jewish women were excluded from the analysis because of their higher prevalence of BRCA mutations.) The models accurately predicted the number of Caucasian BRCA1/2 mutation carriers (25 observed versus 24 predicted by BRCAPRO and 25 by Myriad II). However, the models significantly under predicted Asian mutation carriers (49 observed versus 25 predicted by BRCAPRO and 26 by Myriad II). For BRCAPRO, the difference was especially pronounced for Asian BRCA2 mutation carriers (26 observed versus only 4 predicted); the Myriad II prediction model does not have the ability to differentiate between BRCA1 and BRCA2 mutation risk.

ASCO Perspective
Ramona Swaby, MD, Associate Physician, Fox Chase Cancer Center

"Mutations in the BRCA1 and BRCA2 genes increase a woman's risk of breast and ovarian cancers five-fold. These new findings indicate that more women of Asian descent may be at increased risk of hereditary breast and ovarian cancers than we previously believed, even though they have fewer breast cancer risk factors than Caucasian women, such as dietary fat, obesity, and use of hormone replacement therapy."

"Prediction models for BRCA mutations may need to be revised in light of this new and very important information."

Source: American Society of Clinical Oncology