It has been estimated that about 5 to 10% of all female breast and up to 15% of ovarian cancer cases run in families; in other words, they are hereditary and occur as a result of an inherited predisposition. Of the cases of breast and ovarian cancer that are hereditary, the majority are due to mutations in the BRCA1 and BRCA2 genes. There are additional known and unknown genes that account for the remaining cases of hereditary breast and ovarian cancer.
Features of cancers with a strong inherited component include families with early onset breast cancer (before age 50), ovarian cancer, bilateral breast cancer, male breast cancer, and multiple generations affected with cancer.
We all have genes called BRCA1 and BRCA2. When these genes are working properly, their job is to suppress tumor growth and to protect us from cancer. If a woman inherits a genetic change, or mutation, in one copy of the BRCA1 or BRCA2 gene, she inherits an increased risk to develop breast, ovarian, and other cancers. An inherited mutation in BRCA1 or BRCA2 may be the first step in an accumulation of errors in the genes that can lead to a cell becoming cancerous. This is also why individuals with a BRCA gene mutation are not only more likely to develop breast or ovarian cancer, but are more likely to develop it at a younger age.
All individuals have two copies of each BRCA gene, one copy from each parent. If an individual carries a BRCA mutation, it is likely that it was inherited from one of their parents. There is a 50% chance that siblings and children of a person who carries a mutation will inherit it as well.
Studies have shown that there are specific mutations of the BRCA1 and BRCA2 genes which are common in persons of Eastern European Jewish (Ashkenazi) ancestry. These mutations are called 187delAG and 5385insC in BRCA1, and 6174delT in BRCA2. One in forty Ashkenazi Jewish individuals has one of these three mutations. Ancestry is taken into account when determining the risk to carry a BRCA1 or BRCA2 mutation.
Women who inherit a BRCA1 or BRCA2 mutation have an increased risk for developing breast and ovarian cancers. These risks may vary from family to family and from one individual to another. Women who have an altered BRCA1 or BRCA2 gene have a 45 – 85% chance of developing breast cancer by age 70. Their risk to develop ovarian cancer ranges from 27 – 44% by age 70. A woman who has already had breast cancer has an increased risk to develop a second primary breast cancer. There are also slightly increased risks for other types of cancer as well, including male breast cancer.
The implications of negative results will vary depending on the personal and family history of the individual being tested. Results are more meaningful if someone else if the family has tested positively. It is important to report any genetic testing results of your family members to the genetic counselor to help clarify your own result.
A woman with an altered BRCA gene has several choices that should be discussed with her physician. She might utilize enhanced screening methods to help find cancers at the earliest possible stage when they are most easily treated. Women with BRCA1 or BRCA2 mutations should be sure to practice regular breast cancer screening. This means having yearly mammograms and breast examinations by a physician at frequent intervals. The use of other imaging modalities such as ultrasound and MRI are also important. Screening for ovarian cancer is more difficult because current tests may not find an early-stage ovarian cancer.
Another option is to use a medication to prevent or delay the development of cancer. Examples include Tamoxifen or Raloxifene to decrease the chance of developing breast cancer, or oral contraceptives for premenopausal women to decrease the chance of developing ovarian cancer.
A third option is to have surgery to remove at-risk tissue before cancer develops. An example of this would be risk-reducing mastectomy without a diagnosis of cancer, a type of surgery used to decrease the chances of developing breast cancer. Women can also have their ovaries and fallopian tubes removed, a procedure known as risk-reducing salpingo-oophorectomy, to decrease the chances of developing ovarian cancer. It is important to note that while surgery provides the greatest form of cancer risk reduction, no surgery can completely eliminate one’s chances of getting cancer in the future.
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The decision to have genetic testing for cancer risk is a complicated one. Individuals and families must not only weigh the risks and benefits of testing, they must also consider their unique situations. The process of genetic testing may be emotionally difficult regardless of whether a BRCA1 or BRCA2 mutation is found.
Currently, it is against the law for medical insurance companies or employers to discriminate based on genetic testing. However, genetic information may be considered by other insurance policies, like disability, long term care or life insurance.
The possible advantages of learning BRCA1 and BRCA2 test results include reduced uncertainty about cancer risks. This reduced uncertainty can relieve anxiety and can help individuals make informed decisions about their health care.