BRCA1 and BRCA2
Approximately 10 to 15 percent of all breast cancers are thought to be familial and about one third of these cases are due to an inherited mutation in a BRCA1 or BRCA2 breast cancer susceptibility gene. BRCA1 and 2 mutations are associated with early-onset breast cancer, and some experts call for aggressive Screening of affected persons.
BRCA1 is a gene on chromosome 17 that is known to be involved in tumor suppression. A woman with certain known mutations in BRCA1 has a lifetime risk of 56 to 85 percent for breast cancer and an increased risk of ovarian cancer. Of women with breast cancer, a BRCA1 mutation has been found in 0.3 percent (one of 333) and of women in the general population, in 0.12 percent (one of 833). In Ashkenazi Jewish women (most Jewish people in the United States are of this Eastern European origin), BRCA1 mutations occur in 1 percent.
BRCA2 is another susceptibility gene for breast cancer and is found on chromosome 13. Mutations in BRCA2 confer an elevated breast cancer risk similar to that occurring with BRCA1 mutations. As with BRCA1, BRCA2 is also found in 1 percent of Ashkenazi Jewish women. A woman’s lifetime chance of developing breast and/or ovarian cancer is greatly increased if she inherits an altered BRCA1 or BRCA2 gene.
Women with an inherited alteration in one of these genes may also have an increased chance of developing colon cancer. Men with an altered BRCA1 or BRCA2 gene also have an increased risk of breast cancer (primarily if the alteration is in BRCA2), and possibly prostate cancer. Alterations in the BRCA2 gene have also been associated with an increased risk of lymphoma, melanoma, and cancers of the pancreas, gallbladder, bile duct, and stomach in some men and women.
In a family with a history of breast and/or ovarian cancer, it may be most informative to first test a family member who has the disease. If that person is found to have an altered BRCA1 or BRCA2 gene, the specific change is referred to