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23andMe’s new genetic test for cancer could create a false illusion of safety

23andMe’s new genetic test for cancer could create a false illusion of safety


It tests for three mutations, but many more could predispose you to cancer

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23andMe can now sell genetic tests for cancer risk directly to consumers, after being cleared by the US Food and Drug Administration. Their kit will test for three mutations known to predispose people to developing cancer — but there are hundreds more that it won’t take into account.

This is the first time the FDA has approved a direct-to-consumer genetic test for these three particular mutations on the BRCA1 and BRCA2 genes. (In the past, the FDA approved DTC genetic kits for conditions such as late-onset Alzheimer’s and celiac disease.) Mutations on the BRCA1 and BRCA2 genes are known to be associated with higher risk for prostate cancer, ovarian cancer, and breast cancer. The three mutations 23andMe will test are the most common for those of Ashkenazi Jewish descent — but not the most common mutations in the general population.

Because the test only tests for three mutations, “those tested can get the false illusion that they are not carriers, when in fact they may have other of the hundreds of known functional mutations,” according to Eric Topol, a geneticist at the Scripps Research Institute, in an email to The Verge.

23andMe sequences scattered places of DNA all over the genome, but for people seriously worried about genetic risk, it would be smarter to sequence the entire genome so you’d catch everything, he adds. (This can be done through services such as those from Color Genomics.)

Still, 23andMe CEO Anne Wojcicki argues that even in this limited capacity, the test will make genetic screening more accessible. Under the current system, she writes on the company blog, it is primarily those with a family history of cancer, or who have Ashkenazi Jewish ancestry, who are encouraged to get screened for BRCA mutations. Many people are unaware of their family medical history or ancestry, and those people can now purchase this test without a prescription.

Still, increasing access using a test that doesn’t take into account the majority of the mutations linked to cancer seems less than optimal. “Although this test may help to identify people who have a previously undetected BRCA mutation, there are several limitations and the results may be confusing or misleading without appropriate education,” stated Erica Ramos, president of the National Society of Genetic Counselors.

Both the NSGC and the FDA itself adds that the test shouldn’t be a substitute to seeing a doctor or receiving genetic counseling, and it certainly can’t rule out cancer. “The new offering by 23andMe is better than nothing,” writes Topol. “But we need to (and can even now) do far better.”

Update March 6th, 4:45PM ET: This post has been updated to include a statement from the National Society of Genetic Counselors.