‘Breast Cancer Genes’: How Much Do They Increase Cancer Risk?

'Breast Cancer Genes': How Much Do They Increase Cancer Risk?
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Women who carry genetic mutations in the “breast cancer genes,” called BRCA1 and BRCA2, have about a 70 percent chance of developing breast cancer in their lifetimes, according to a new study.

The findings are based on an analysis of nearly 10,000 women with mutations in either the BRCA1 or BRCA2 gene, mutations that are known to increase the risk of breast and ovarian cancer. The new study is more rigorously designed than some earlier research that looked at how much the risk for these cancers increases in women who have these genetic mutations.

But the new study also found that breast cancer risk in women with these mutations could vary — by as much as twofold — depending on whether the women had specific mutations within their genes. In addition, having close family members with the disease also indicated a greater increase in risk, the study found.

The findings suggest that health professionals who council women who have BRCA1 or BRCA2 mutations about their risk of breast cancer should take into account both a patient’s family history and the particular location on the gene of the individual’s mutation, the researchers said. [6 Foods That May Affect Breast Cancer Risk]

The findings “demonstrate the potential importance of family history and mutation location in risk assessment” of breast cancer, the researchers said.

Prior to the study, scientists knew that women with mutations in the BRCA1 and BRCA2 gene are at increased risk for breast and ovarian cancer. Previous studies have estimated that the lifetime risk of breast cancer ranges from 40 to 87 percent for women with BRCA1 gene mutations, and 27 to 84 percent for women with BRCA2 gene mutations, according to the researchers. In contrast, the average American woman has about a 12 percent chance of developing breast cancer by age 85, according to the Susan G. Komen foundation, a nonprofit organization that funds breast-cancer research.

Many earlier studies on this topic were “retrospective,” meaning they included information from women with these mutations who already had breast or ovarian cancer. Those studies used information about the women’s family history to help estimate the…