Genetic Testing: Who and Why?

Women often wonder about their personal risk of breast cancer in relation to their family history. When a woman has a relative who has had breast cancer, it often raises increased concern about her own risk. The good news for most women is that only about 10% of breast cancers are clearly related to a genetic cause. The other good news is that for some women, we are able to more precisely estimate their risk by performing genetic testing and modify our approach to their care to keep them healthy.

The genes most often associated with breast cancer are BRCA-1 and BRCA-2. Women who carry a mutation in one of these genes are at a much higher risk of developing breast cancer (65-75% over their lifetimes). These mutations also put women at risk for ovarian cancer (39-46% for BRCA-1 and 12-20% for BRCA-2), and men who carry these mutations are at higher risk for breast (yes, men can get it!) and prostate cancers. Breast cancers in BRCA-mutation carriers tend to be more aggressive and occur at younger ages, which makes these mutations particularly frightening.

In the United States, approximately 1:300 to 1:800 individuals carries a BRCA mutation. This rate is increased in certain ethnic groups; in Ashkenazi Jews the rate is closer to 1:40. The American Congress of Obstetrics and Gynecology (ACOG) and other organizations recommend testing for BRCA mutations in women who have at least a 20-25% chance of testing positive. These women include those with:

  • a personal history of both breast and ovarian cancer
  • a personal history of ovarian cancer and a close relative (mother, sister, daughter, aunt, grandmother, or granddaughter) with ovarian cancer, premenopausal breast cancer, or both
  • Ashkenazi Jewish descent and breast cancer diagnosed by the age of 40 or ovarian cancer at any age
  • a personal history of breast cancer by age 50 and a relative with ovarian cancer at any age or a male relative with breast cancer
  • a close relative who is known to carry a BRCA mutation

Testing should be considered in women who have at least a 5-10% chance of testing positive, including women with:

  • a personal history of breast cancer by the age of 40
  • a personal history of ovarian cancer, fallopian tube cancer, or primary peritoneal cancer at any age
  • a personal history of cancer in both breasts (particularly if the first was diagnosed by the age of 50)
  • a personal history of breast cancer at any age with two or more close relatives with breast cancer at any age
  • no personal history of the above but a close relative who meets these criteria

It is important to remember that these mutations can be carried by both men and women, so your father’s family is as important as your mother’s in assessing your risk.

Why bother to be tested? It turns out that if we know you carry a BRCA mutation, we can do increased screening for breast and ovarian cancer to detect these cancers at early stages and offer treatments that greatly reduce your risk of developing cancer in the first place. For example, we recommend that patients who test positive, start undergoing mammograms at an early age and get an annual breast MRI as well. We also screen closely for ovarian cancer with ultrasounds and blood tests (currently, the jury is out as far as doing these tests in non-carriers goes–it doesn’t seem to help). Some women with BRCA mutations opt to undergo preventive mastectomy (removal of the breasts) and oophorectomy (removal of the ovaries) before cancer can develop, which reduces their cancer risk by over 90%.

Do you think you qualify for testing or have further questions? Give us a call at HealthCare for Women. We can help you sort through this complicated issue to reach the decision that is best for you and your family.