Family History Raises Breast Cancer Risk Despite Absence Of BRCA Mutations, Study Finds

Main Category: Breast Cancer
Also Included In: Genetics
Article Date: 20 Nov 2008 - 8:00 PST

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Women with a strong family history of breast cancer have a four times greater risk for the disease than women in the general population, even if they do not carry a mutation of the BRCA gene, according to a study presented Monday at the American Association for Cancer Research's annual International Frontiers in Cancer Prevention Research meeting in Washington, D.C., HealthDay/U.S. News and World Report reports (Doheny, HealthDay/U.S. News and World Report, 11/17). The BRCA1 and BRCA2 genese are linked with aggressive hereditary breast cancer and an increased risk of ovarian cancer, and tests are available to determine if women are carriers of the mutations, the AP/Minneapolis Star Tribune reports. However, the gene mutations only account for about 15% of all breast cancer cases. Even among families with a history of breast cancer, a BRCA gene is discovered only in roughly one out of five families, suggesting that other factors are at work, according to study author Steven Narod, a University of Toronto cancer specialist (Neergaard, AP/Star Tribune, 11/17).

For the study, Narod and colleagues tracked nearly 1,500 Canadian women who had tested negative for the BRCA1 and BRCA2 mutations but had a strong family history of breast cancer, which was defined as having two or more relatives diagnosed with breast cancer before age 50 or three relatives with breast cancer at any age. The researchers compared the rates of breast cancer among the group against rates found in regional cancer registries of the general population. Over the six-year study period, women with family histories of breast cancer were four times more likely than the general population to develop the disease. Women younger than age 40 in the family history group had a 15 times greater risk of developing the disease than women in the general population (HealthDay/U.S. News and World Report, 11/17). The study also found that women in the family history group did not show an increased risk of ovarian cancer (AP/Star Tribune, 11/17).

Kelly Metcalfe -- an associate professor of nursing at the University of Toronto and an author of the study -- said the findings suggest there are unknown genetic mutations that are linked to breast cancer. Metcalfe said the average woman has about a 10% lifetime risk of developing breast cancer. By comparison, a typical woman with a BRCA mutation has an 80% lifetime risk, and women with no mutation but a strong family history have about a 40% lifetime risk, she said (HealthDay/U.S. News and World Report, 11/17).

Beth Peshkin, a genetics counselor at Georgetown University, said the findings provide important information for women considering BRCA testing. She added that the results are "contrary to what I think the perception is. Unless a mutation is identified in the family, a negative test result doesn't provide reassurance." Narod said that although newer tests for other genes are expected to be coming to the market, "the family history is a much stronger predictor." He recommended that women with a strong family history take the anti-breast cancer drug tamoxifen and undergo MRI screenings in addition to regular mammograms (AP/Star Tribune, 11/17).

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