A recent study points to women opting for unnecessary mastectomies after taking private DNA tests that indicate a heightened risk for breast cancer due to mutated genes that are particularly prevalent in Ashkenazi Jews.

“For each diagnosis potentially prevented, around three women could be exposed to needless breast surveillance or prophylactic treatment,” the researchers wrote on Sept. 14 in The Lancet. Current estimates of the prevalence of pathogenic breast-cancer genes—about 30% of women and more than 50% of U.S. women—could mean “one needless mastectomy for every true case of breast cancer,” the scholars add.

University of Manchester researchers told JNS that existing predictive models overstate the risks for Ashkenazi Jewish women of developing breast cancer. 

Around one in 40 people of Ashkenazi Jewish descent carry a faulty BRCA1 or BRCA2 gene, significantly higher than the general population’s prevalence of one in 400. While most cases of breast and ovarian cancer are not genetically driven, testing and the identification of the mutations can lead people to opt for preventive measures, such as breast- or ovary-removal surgery.

Scientists at the University of Exeter analyzed data from more than 450,000 people between 40 and 69 years old. Their findings indicated that carrying a disease-causing BRCA variant was linked to an 18% breast-cancer risk for BRCA2 and a 23% risk for BRCA1 by the age of 60. The risks rose to 24% and 45%, respectively, if a close relative had the same condition.

Traditionally, most people learned about genetic risk in clinical visits following symptoms or concerns over family history, but with the rise of at-home DNA testing kits and participation in genetic research, people are increasingly being informed of their genetic risk without any personal link to the cancer. Researchers are concerned about those who might be informed in a non-clinical setting that they have as high as an 80% risk of developing breast cancer.

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