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A simple blood test can determine whether someone carries a BRCA1 or BRCA2 genetic mutation that predisposes them to breast cancer. Women with BRCA mutations have an 85% lifetime risk for breast cancer and a 60% risk for ovarian cancer. These mutations account for most hereditary breast and ovarian cancers, but experts suspect other as yet unidentified mutations increase risk as well. These undiscovered hereditary mutations may explain why many women who have a family history of breast cancer are surprised when genetic testing finds no evidence of a BRCA mutation.
Recent Canadian research finds that women who have a significant family history of breast cancer but have no known BRCA mutation have a 30â€“40% lifetime risk of developing breast cancer. That’s much less than someone with a BRCA mutation, but far greater than the general population. Researchers evaluated 1,492 women from 365 families over five years. The women had strong family history of breast cancer — two or more breast cancers among close relatives under the age of 50 or three cases of breast cancer among close relatives at any age — but no known genetic mutations. Their risk of developing breast cancer was found to be four times that of the general population. The risk was 15 times greater for participants under age 40 compared to women age 40 who had no such family history.
These study results may help to underscore the importance of increased screening, chemoprevention, and other preventative measures for women who have a family history of breast cancer but no known genetic mutation.
More details at http://www.nature.com/bjc/journal/v100/n2/abs/6604830a.html
June 5, 2009