Can a direct-to-consumer genetic test tell me whether I will develop cancer?
While a direct-to-consumer genetic test can estimate your risk, it cannot tell you for certain whether you will or will not develop certain forms of cancer. Many other factors, including gender, age, diet and exercise, ethnic background, a history of previous cancer, hormonal and reproductive factors, and family history also contribute to a person’s overall cancer risk.
The U.S. Food and Drug Administration (FDA) has allowed at least one direct-to-consumer genetic testing company, 23andMe, to offer a test for cancer risk. The test looks for three specific variations in two genes: BRCA1 and BRCA2. These variations are associated with an increased risk of breast cancer, ovarian cancer, and potentially other forms of cancer in people of Ashkenazi (eastern European) Jewish ancestry.
Researchers estimate that 5 to 10 percent of all cancers run in families. Some of these cancers are associated with inherited mutations in particular genes, such as BRCA1 or BRCA2. More than 1,000 variations in each of these genes have been associated with an increased risk of cancer. However, the FDA-approved direct-to-consumer genetic test analyzes only three of these variations. The variations included in the test are much more common in people of Ashkenazi Jewish background than in people of other ethnicities, so if you are not of Ashkenazi Jewish heritage, the results may not be useful to you.
Because the variants included in the test are uncommon, most people will have a negative result. A negative result does not mean that you will never get cancer. Similarly, a positive result (one that indicates a cancer-related genetic variation) does not mean that you will definitely develop cancer.
Direct-to-consumer genetic testing for cancer risk can be stressful and anxiety-producing. Health professional organizations and patient advocacy groups strongly recommend that people considering genetic testing for BRCA1 and BRCA2 variations, including those included in direct-to-consumer genetic tests, talk with a genetic counselor about the reasons they want to undergo testing and what the results could mean for their health.