Should I be tested for the breast cancer gene?

(This article was first printed in the March 2004 issue of the Women's Health Watch. For more information or to order, please go to http://health.harvard.edu/women.)

Q I was astounded to read that women who test positive for the breast cancer gene have as much as an 80% risk of getting breast cancer. Shouldn’t we all be tested?

A Two major genes are associated with susceptibility to both breast cancer and ovarian cancer — BRCA1 and BRCA2. In 2003, the New England Journal of Medicine reported that inherited mutations in either of these genes confer a 60%–85% lifetime risk of breast cancer and a 20%–40% lifetime risk of ovarian cancer. Since the average woman’s lifetime risk of getting breast cancer is 12% and ovarian cancer, 1.2%, the implications of having such a mutation are quite serious.

Nevertheless, genetic testing isn’t appropriate for most women. The vast majority of breast cancer is not caused by hereditary mutations. Moreover, inheriting a mutation doesn’t necessarily mean you’ll develop the disease.

The only women who should consider it are those whose family history suggests a heightened risk. That includes having a mother, sister, or daughter with breast cancer, or 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, may also prompt you to consider testing. Risk is also heightened if you have 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; or Ashkenazi Jewish ancestry.

If you fall into any of these groups, you need to carefully weigh the pros and cons of testing 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.

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.

You need to think in advance about what you’re willing to do if you test positive. Most women will want to follow a schedule of semiannual or annual clinical breast exams and mammograms, starting at age 25–35. But fewer women are willing to consider prophylactic 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.

There are other considerations. 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. Also, genetic testing may not be completely covered by your insurer, and it’s very expensive — issues you need to resolve before having blood drawn.