Should you be tested for the breast cancer gene?
Two major genes are associated with increased risk of breast cancer and ovarian cancer — BRCA1 and BRCA2. In 2003, the New England Journal of Medicine reported that women who inherit mutations in either of these genes had a 60%–85% lifetime risk of getting breast cancer and a 20%–40% lifetime risk of getting ovarian cancer. These are significantly higher than the average woman's lifetime risks, which are 12% for breast cancer and 1.2% for ovarian cancer.
Nevertheless, genetic testing isn't appropriate for most women. Most breast cancers are not caused by hereditary mutations. Moreover, inheriting a mutation doesn't necessarily mean you'll develop the disease. The only women who should consider testing are those whose family history suggests a heightened risk. This includes women who have:
- A mother, sister, or daughter with breast cancer
- A grandmother, aunt, niece, or half-sister who developed breast cancer before age 40
- A personal history of breast or ovarian cancer before age 40, particularly if you're of Jewish ancestry
- Two or more first- or second-degree relatives in a single bloodline with breast cancer or breast and ovarian cancers
- A family member with cancer in both breasts, or both breast and ovarian cancer
- A male family member with breast cancer
- Ashkenazi Jewish ancestry.
If you fall into any of these groups, you need to think carefully about testing. You may want to weigh the pros and cons with your doctor or a genetic counselor. It's a simple blood test, but interpreting the results and coping with them can be very difficult. Some things to think about before you have your blood drawn include:
- If you test negative for a mutation identified in a relative with breast or ovarian cancer, your risk is probably about average. But if no one else in your family has been shown to carry a mutation, a negative result is harder to interpret. It may mean that you didn't inherit the mutation or that an unidentified gene or mutation is contributing to your family's cancers.
- What are you willing to do if you test positive? Most women will want to follow a schedule of semiannual or annual clinical breast exams and mammograms. But fewer women are willing to consider mastectomy, which markedly reduces risk in women with positive BRCA1 and BRCA2 tests. Removing the ovaries, especially before age 40, can also cut breast cancer risk by as much as 60% and ovarian cancer risk by 90% or more.
- How will the result affect future insurance coverage? Most states have genetic privacy laws that prevent discrimination by health insurers based on genetic information. But these don't necessarily apply to life or disability insurance.
May 2004 Update