At-home genetic testing in determining breast cancer risk: What you need to know
By Lori White, PhD
Many women are understandably curious about their personal risk for breast cancer. In 2018, an estimated 266,120 new cases of invasive breast cancer are expected to be diagnosed in women in the U.S., along with 63,960 new cases of non-invasive (in situ) breast cancer. (1) If the *average* risk for a woman to develop breast cancer is about 12%, how can women determine if they are above or below average? Analyzing your DNA seems like a good place to start.
We know that about 10% of all breast cancers are caused by a genetic susceptibility that is inherited. In the 20+ years since the most well-known culprits, BRCA1 and BRCA2, have been characterized, we have learned that there are thousands of mutations in these two genes that explain the high occurrence of breast cancer in affected families. In addition to these two genes, there are dozens of other genes that are also associated with an elevated risk for breast cancer. The primary concerns with the testing that is now offered by at-home, consumer testing, such as 23andMe, is the test’s very limited scope, and that consumers may wrongly assume that a negative result means that they are not at increased risk for breast cancer.
The 23andMe test only reports three very specific mutations in the BRCA genes that are most commonly found in people of Ashkenazi Jewish ancestry. When the availability of this particular test was announced, acting director Donald St. Pierre of the FDA’s center that issued the authorization stated, “This test provides information to certain individuals who may be at increased breast, ovarian, or prostate cancer risk and who might not otherwise get genetic screening and is a step forward in the availability of direct-to-consumer genetic tests. But it has a lot of caveats. While the detection of a BRCA mutation on this test does indicate an increased risk, only a small percentage of Americans carry one of these three mutations, and most BRCA mutations that increase an individual’s risk are not detected by this test. The test should not be used as a substitute for seeing your doctor for cancer screenings or counseling on genetic and lifestyle factors that can increase or decrease cancer risk.”
Genetic testing can be a powerful source of information to understand an individual’s risk for developing cancer, if it is done properly. Today, genetic testing is readily available, and out-of-pocket costs have decreased dramatically. Most often, if there are certain risk factors (2) in your family, genetic testing is covered by insurance, and your privacy is protected by HIPAA and the Genetic Information Nondiscrimination Act.
If we stop the evaluation at genetic testing, though, we wouldn’t address the up to 42% of cancers that are caused by lifestyle factors. Comprehensive personalized risk assessment explores the genetic factors indicated by the family’s cancer history AND asks questions about “fixed” and “modifiable” risk factors. “Fixed” risk factors are parts of our medical history that don’t change over time: current age, onset of puberty, and age at birth of first child. Other health history factors include breast density, menopause status, and use of hormone replacement therapy. “Modifiable” risk factors are related to lifestyle. These are factors that we can influence by changes in diet, exercise, tobacco use, alcohol consumption and UV radiation exposure. Evaluation of all of these risk factors can help determine your personal risk for breast cancer. This information can then be used to develop a health plan to minimize your risk and determine the best type and schedule for breast cancer screening. At-home testing doesn’t adequately answer concerns breast cancer risk. Opt instead for a more comprehensive understanding.
- Breast cancer diagnosed before age 50 years
- Cancer in both breasts in the same woman
- Both breast and ovarian cancers in either the same woman or the same family
- Multiple breast cancers in the family
- Two or more primary types of BRCA1– or BRCA2-related cancers in a single family member
- Cases of male breast cancer
- Ashkenazi Jewish ethnicity