BRCA Genes. Inherited mutations in genes known as BRCA1 or BRCA2 are responsible for 30 - 50% of hereditary breast cancers, ovarian cancers, or both in families with a history of these cancers. According to some studies, the risk each gene carries is:
- Between 25 - 35% of BRCA1 carriers develop breast cancer by age 70.
- Between 35 - 50% of BRCA2 carriers develop the disease. BRCA2 genes also increase the lifetime risk of breast cancer in men.
These mutations are present in only about 0.5% of the overall population. However, certain ethnic groups -- such as Jewish women of Eastern European (Ashkenazi) descent -- have a higher prevalence (2.5%) of BRCA gene mutations.
Screening Guidelines for BRCA Genes. In 2005, the U.S. Preventive Services Task Force (USPSTF) released updated guidelines for BRCA testing. While women at high risk should be tested, the USPSTF does not recommend routine genetic counseling or testing for BRCA genes in low-risk women (no family history of BRCA 1 or 2 genetic mutations).
ESR Genes. Genetic variations in estrogen receptor genes (ESRs) may increase the risk for some women but offer protection to others. Mutations in the ESR1 and ESR2 genes may be associated with breast cancer susceptibility for Ashkenazi women over age 50 years.
Other Genetic Factors. Mutations in the tumor suppressor gene p53 are more common in the breast cancer tumors of African-American women than Caucasian women. Researchers have also identified other defective genes that contribute to breast cancer, such as NOEY2 (which is inherited from the father), CHEK2, and a mutant gene for the rare disorder ataxia-telangiectasia. (The disease itself is rare, but 1% of the population carries a single copy -- enough to increase the risk for breast cancer.) Finally, Cowden's syndrome is an inherited disorder caused by a defective PTEN gene that is associated with a higher risk of breast cancer.
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