An analysis of past studies on mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 suggests that estimates of penetrance (or the likelihood that mutation carriers will develop breast cancer during their lifetime) have been exaggerated. This can happen because a woman’s risk of developing breast cancer is likely to be associated not only with the specific genetic mutation but also with many other risk factors, concludes a study in the August 21 issue of the Journal of the National Cancer Institute. Author Colin B. Begg is a researcher at Memorial Sloan-Kettering Cancer Center in New York.

Wylie Burke, professor and chair of medical history and ethics and adjunct professor of medicine, and Melissa Austin, professor of epidemiology and adjunct professor of medicine, wrote accompanying editorial saying that the new study underscores the pitfalls of failing to address the complexity of disease risk and its implications for disease prevention. They point out that nongenetic risk factors have been shown to influence the outcome of genetic risk in many other settings. For example, they say, smoking, diet, and exercise can modify the effect of genetic risk for heart disease.