A large study funded by the National Institutes of Health today provided the clearest picture yet of the prevalence in the U.S. population of mutations in two genes associated with an increased risk of breast cancer. The genes are called Breast Cancer 1 (BRCA1) and Breast Cancer 2 (BRCA2). In addition, the study identified key predictors for assessing which women are most likely to carry these genetic mutations.


Each year, approximately 200,000 women in the United States are diagnosed with breast cancer. The majority of breast cancer cases are caused by genetic changes that occur during a woman's lifetime and not by genetic mutations inherited from her parents. However, researchers estimate that inherited mutations play a role in anywhere from 5 to 27 percent of all breast cancer cases. In the mid 1990s, researchers found that mutations in the BRCA1 and BRCA2 genes are a major cause of the hereditary form of the disease. Women inheriting these mutations have a 40 to 85 percent lifetime risk of developing breast cancer, as well as an increased risk of ovarian cancer.


To date, most of the studies on BRCA1 and BRCA2 mutations have focused on families known to be at high risk for breast cancer and on women who develop breast cancer at a relatively young age. The new study, published today in the journal Cancer Research, looked at the prevalence and predictors of BRCA1 and BRCA2 mutations in under-studied groups of women, such as African Americans and older women.


"Studies of any notable size have focused almost exclusively on white women and young women. This research clearly was needed to improve our means of assessing the likelihood of carrying BRCA1 and BRCA2 mutations in a wider spectrum of women," said one of the study's lead investigators, Elaine Ostrander, Ph.D., chief of the Cancer Genetics Branch in the National Human Genome Research Institute's Division of Intramural Research. Dr. Ostrander was previously head of the genetics program at the Fred Hutchinson Cancer Research Center, which is the institution that led the study.


The researchers examined the prevalence and predictors of BRCA1 and BRCA2 mutations in 1,628 women with breast cancer and 674 similar women without breast cancer, all of whom were participants in the National Institute of Child Health and Human Development's (NICHD's) Women's Contraceptive And Reproductive Experiences (CARE) study. The women involved in the study were white and African American women, ages 35 to 64, who lived in the Atlanta, Detroit, Los Angeles, Philadelphia and Seattle metropolitan areas.

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