In the 1990s, mutations in two genes, BRCA1 (BReast CAncer 1) and BRCA2 (BReast CAncer 2), were shown to be involved in inherited breast and ovarian cancers. It is estimated that 40% to 90% of families with an inherited form of breast or ovarian cancer have a defective copy of the BRCA1 or BRCA2 gene.
BRCA1 and BRCA2 are called "tumor suppressor genes" because they make proteins that help prevent the cells from forming tumors. If one of these genes is changed through a mutation, the protein may not do its job, making it easier for a tumor to develop.
Women who inherit a mutated copy of either the BRCA1 or BRCA2 gene have an increased chance of developing breast or ovarian cancer. In addition, there may be an increased risk for other cancers.
According to the National Cancer Institute, about 12% of women (120 out of 1,000) in the general population will develop breast cancer sometime during their lives. But the risk jumps to about 60% (600 out of 1,000) for women who have inherited a harmful mutation in BRCA1 or BRCA2. This means they are about five times more likely to develop breast cancer than a woman who does not have such a mutation.
About 1.4% (14 out of 1,000) of women in the general population will be diagnosed with ovarian cancer during their lives. But inheriting a harmful mutation in BRCA1 or BRCA2 means 15% to 40% of women (150–400 out of 1,000) will be diagnosed with ovarian cancer sometime during their lives.
Harmful BRCA1 mutations may also increase a woman's risk of developing cervical, uterine, pancreatic, and colon cancer. Harmful BRCA2 mutations may additionally increase the risk of pancreatic cancer, stomach cancer, gallbladder and bile duct cancer, and melanoma.
Men with harmful BRCA1 mutations also have an increased risk of breast cancer and, possibly, of pancreatic cancer, testicular cancer and early-onset prostate cancer. However, male breast cancer, pancreatic cancer, and prostate cancer appear to be more strongly associated with BRCA2 gene mutations.
Should You Be Tested?
You are more likely to have a BRCA1 or BRCA2 mutation if you have a family history of breast or ovarian cancer. Meeting with a genetic counselor or a doctor trained in genetics will help you decide if genetic testing is right for you.
Why Does A Genetic Counselor Need My Medical Records?
Medical records can be very helpful to your genetic counselor or doctor. Medical records from family members who have had breast or ovarian cancer at younger ages, or from male family members who had breast cancer, are particularly helpful. The family member who had cancer (or his/her next of kin) will need to sign a medical record consent form from the hospital where he or she was treated to get the records released to you. Sometimes medical records are not available on family members who died a long time ago, but it may be possible to get a death certificate from the town or state where they lived.