Women who inherit mutations of certain genes are at an 82% lifetime risk of developing breast cancer and have a 23%-54% risk of ovarian cancer, according to a study that analyzed the health records of more than a thousand Jewish women. The study, appearing in the October 24 edition of the journal Science, also found that exercise and maintaining a healthy weight during adolescence delays the onset of breast cancer even in women who have mutations of the BRCA1 or BRCA2 gene. Lead researcher Mary-Claire King of the University of Washington said the study found that women who exercised actively when they were young--either dancing, participating in team sports, or just walking a lot--and who maintained a healthy weight through the age of 21 were somewhat protected from breast cancer. "If they carried the mutation, they still had a very high risk, but their age of diagnosis was pushed to later in life," she said.
The study helps to clear up some of the confusion about the risks associated with the BRCA1 and BRCA2 gene mutations, said Kenneth Offit, a physician and researcher at Memorial Sloan-Kettering Cancer Center in New York. Earlier studies had suggested that the breast cancer risk from the gene mutations ranged from 25% to 80%. The new study puts the lifetime risk at 82%. For ovarian cancer, the study found the lifetime risk was 54% for BRCA1 and 23% for BRCA2 mutations.