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Most Ashkenazi Jewish women should be tested for breast cancer genes, study finds

December 29, 2009 |  4:03 pm

Most women of Ashkenazi Jewish descent should be offered testing for the most common genetic mutations that cause breast and ovarian cancer, Canadian researchers have found. About 1% of the women they tested had a mutation in either the BRCA1 or BRCA2 gene, which carries a very high risk of disease. Women with the mutated  BRCA1 gene have lifetime risk of breast cancer of about 70% and a 30% to 40% risk of ovarian cancer. Those with a mutated BRCA2 gene have a 50% risk of breast cancer and a 20% risk of ovarian cancer. Although the defective genes occur in about 2.5% of the Ashkenazi Jewish population, women are not eligible for genetic testing under Medicare guidelines or those in force in Canada unless they have a strong family history of breast or ovarian cancer or have one of the diseases.

Ashkenazi Jews, who now account for an estimated 80% of the world's Jews, were originally from Germany. They have a very high incidence of certain genetic diseases, including Tay-Sachs, Niemann-Pick, Gaucher and Canavan diseases, Bloom Syndrome and Fanconi anemia.

Dr. Steven A. Narod of the Women's College Research Institute in Toronto and his colleagues placed an ad in a major Canadian newspaper looking for Ashkenazi women who wished to undergo genetic testing. Within two weeks, they had more than 2,100 responses. They enrolled 2,080 women, most of them with no family history of the disease, who reported to the clinic to leave a blood or saliva sample. The team reported in the Journal of Clinical Oncology that 22 of the women, 1.1%, carried one of the three common mutations. Those women who had a mutation were invited into the clinic for counseling about their risk of developing one of the cancers. Many women who have the BRCA1 mutation choose to have their breasts removed prophylactically to prevent development of cancer.

The team also identified 33 first-degree relatives who were eligible for genetic testing. Twenty-six of them agreed to the test and eight were found to carry the mutated gene. Overall, the team thus identified 30 women who carried a gene predisposing them to cancer and who would not have known it if they had not been given the test. Based on their findings, Narod and his colleagues concluded, the test should be offered to all women of Ashkenazi ancestry.

-- Thomas H. Maugh II

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