Will you develop breast or ovarian cancer one day? No one can tell for sure. But for a relatively small number of women with family or personal histories of these cancers, genetic testing may provide a partial answer.
Genetic testing involves analysis of your DNA. When you have a genetic test to assess your risk of a disease, the test determines whether your DNA contains a genetic change (mutation) that has also been found in a number of people with that disease. This type of test is possible only for certain diseases that run in families. Only 5 percent to 10 percent of breast cancers are caused by such a genetic change.
If you have mutations in either of two breast cancer susceptibility genes — BRCA1 and BRCA2 — your risk of breast or ovarian cancer is significantly higher than that of a woman without such a mutation. How much higher depends on a number of other factors, including your age and the ages at which women in your family developed breast or ovarian cancer.
Who should consider genetic testing?
Out of the 212,920 new cases of breast cancer diagnosed in the United States last year, only 10,000 to 20,000 cases were inherited — and only a fraction of those were linked to BRCA1 and BRCA2 mutations. This small number means that for the majority of women who develop breast cancer, the cancer occurs sporadically and isn't caused by hereditary factors.
The picture changes if two or more of your first-degree relatives — parents, siblings, children, or one of each — have developed breast or ovarian cancer. In that case, genetic counseling is recommended. Genetic counseling is a communication process between you and a genetic counselor. The genetic counselor takes a detailed family and medical history, assesses your risk of developing cancer, discusses risks and benefits of genetic testing, and determines your options. A genetic counselor can help you develop an appropriate strategy for dealing with your cancer risk in the context of your individual situation.
If, through genetic counseling, you discover that your risk of carrying a BRCA1 or BRCA2 mutation is high, you may decide to undergo genetic testing to see if you actually do have a mutated gene.
Who is at increased risk of having a mutated BRCA1 or BRCA2 gene?
Certain factors increase your risk of having a BRCA mutation. You might be at increased risk of having a BRCA gene change if you have:
- A personal history of breast cancer diagnosed at a young age, breast cancer affecting both breasts (bilateral breast cancer), or both breast and ovarian cancers
- A family history of breast cancer in two or more close relatives, such as your parents, siblings and children
- A family member who developed breast cancer before age 50 on either your mother's or your father's side of the family
- A family history of breast cancer in more than one generation
- A male relative with breast cancer
- A family member who has both breast and ovarian cancers
- A family member with bilateral breast cancer
- A frequent occurrence of ovarian cancer within your family
- A positive BRCA1 or BRCA2 genetic test in a relative
- Ashkenazi (Eastern European) Jewish ancestry, with or without a family history of breast or ovarian cancer
Researchers have discovered that 2.3 percent of women of Ashkenazi descent carry a BRCA mutation — about five times greater than that of the general population.
How much higher is your risk of cancer if you have a BRCA mutation?
If you have a BRCA mutation, your chances of developing breast or ovarian cancer during your lifetime are substantially higher than are the rates for the general population.
| Risk of developing cancer by age 70 | Average risk | With BRCA1 mutation | With BRCA2 mutation |
|---|---|---|---|
| Breast cancer | 13% | 60% to 80% | 60% to 80% |
| Ovarian cancer | 1.5% | 20% to 45% | 15% to 27% |
Many factors come into play in risk estimates, including differences in the gene mutation, the location of the mutation and the woman's ethnic background.
A study of more than 1,000 women of Ashkenazi Jewish descent provides what could be a clearer picture of the breast and ovarian cancer risks for women with BRCA mutations. Researchers identified a lifetime risk of breast cancer mutations of 20 percent by age 40, 55 percent by age 60 and 80 percent by age 80 in Ashkenazi Jewish women with BRCA. The lifetime risk of ovarian cancer was 54 percent for women with BRCA1 mutations and 23 percent for women with BRCA2 mutations.
A tough call
The value of genetic testing for breast cancer is a matter of debate. Ideally, it should be done only if your personal or family history suggests you might be susceptible to hereditary cancer. Even then, you'll need expert guidance from a genetic counselor to interpret the test results adequately and explore the options for managing your risk.
If your doctor or genetic counselor recommends genetic testing, you may be faced with a difficult decision. Genetic testing is expensive, and it may or may not be covered by your insurance. Also consider how you'll handle learning the test results — whether positive or negative. Ultimately, the choice of whether or not to have genetic testing done is yours.
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