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Risk of breast and ovarian cancer in women with ancient mutations
in BRCA1 or BRCA2
  
By Bijal P. Trivedi

Jewish women with primary invasive breast cancers were tested for mutations in the BRCA1 or BRCA2 genes as aprt of a study to determine the risk of developing breast tumors. The 861 women and their female relatives were part of the collaborative New York Breast Cancer Study, which drew participants from 11 cancer centers in the New York City area.

The results of the study to date were reported as late-breaking research news by Mary-Claire King at the annual meeting of the American Association of Human Genetics in Philadelphia this week. King is a medical geneticist at the University of Washington School of Medicine in Seattle where the women's blood samples were sent for gene sequencing.

The researchers tested each person for three ancient mutations—BRCA1 185delAG, BRCA1 5382insC, and BRCA2 6174delT—and found that about ten percent of the women were positive for one of them. (In the complex world of breast cancer genetics, it is worth noting that 90 percent of the Jewish women with breast cancer did not carry one of these mutations.) Using gene screening results and family histories from the patients who tested positive for a BRCA1 or BRCA2 mutation, the researchers calculated the risk of breast cancer in female relatives carrying a mutation in either BRCA1 or BRCA2: The average risk by age 40 is19 percent, by age 50 is 35 percent, by 60 is 53 percent, and by age 70 is 68 percent. By the time a woman who carries a mutation reaches 80, her risk of breast cancer is 82 percent.

Researchers also determined the risk of ovarian cancer in relatives with BRCA1 mutations: The average risk by 40 is one percent, by 50 is 20 percent, by 60 is 40 percent, by 70 is 47 percent, and by 80 is 55 percent. The risks of developing ovarian cancer at any age due to BRCA2 mutations are much lower.

The research team noted that "no extrinsic factor completely precluded breast cancer among women with mutations...." In fact, "risks of breast cancer among women with BRCA1 and BRCA2 mutations are increasing with time, as are risks of breast cancer among women generally," the researchers noted. However, there is no clear explanation for this apparent trend.

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