Lifestyle 4 min read

The First Direct-To-Consumer BRCA Cancer Gene Test Comes With Caveats

For most consumers, the 23andMe test is limited in assessing cancer risk.

By Dyani Sabin featured image

On Tuesday March 6, the Food and Drug Administration approved the first direct-to-consumer test that reports on BRCA1- and BRCA 2-related genetic risk for breast, ovarian, and prostate cancer.

The approval comes on the heels of a change in the FDA’s regulatory requirements last November, which paved the way for companies to market new genetic health risk tests. Until this test, patients had to go to doctors or genetic counselors to get information about their genetic cancer risk. With the newly-approved BRCA test, however, people can send their saliva samples directly to 23andMe.

Normally, BRCA1 and BRCA2 genes suppress tumor growth. But about one in 400 people have a variation in these genes that prevents them from working properly, increasing the risk of developing cancer. The 23andMe test reports on three of these BRCA variants, which are seen most commonly in people of Ashkenazi Jewish descent. Women with one of the three variants may have a 40 to 60 percent increased risk of developing breast cancer over their lifetime without any other risk factors involved.

Despite the seriousness of these mutations, some healthcare professionals are hesitant about the usefulness of 23andMe’s new test. Because it only reports on three BRCA mutations that are not common in the general population, the test will not be very informative for most people it, says Carmen Williams, a genetic counselor at Northwestern University Feinberg School of Medicine. There are more than 1,000 known BRCA mutations that have the potential to increase cancer risk. “It is a very limited test, and so a negative or normal result on this shouldn’t be interpreted as a complete rule out,” she says.

“I think the potential benefit to something like this is if someone does carry a BRCA mutation and if they do find out about that through this test and follow up appropriately, then they will potentially have discovered a high risk for cancer that they might not have otherwise known about,” Williams says.

But customers who get a positive result on the 23andMe test, may still need to be re-tested.

In the statement approving the test, the FDA said it’s not a substitute for cancer screening or having a conversation with a doctor. After a doctor or genetic counselor orders a clinical genetics test to back up the results, they can help patients understand their risk, plan for additional cancer screenings, and discuss preventive measures, Williams says.

The reason for the discrepancy is that 23andMe uses a different method of genetic testing than a cancer geneticist would order from a lab. The company uses genotyping, which involves looking for short sequences within genes to quickly identify mutations. “We are a genotyping platform and do not have the technical capability to sequence the full BRCA1 and BRCA2 genes to uncover all possible variants in those genes,” says Shirley Wu, director of product science at 23andMe.

Because of this, its accuracy is more limited. “It has a higher potential to provide someone a false positive result than the type of technology we use in a clinical test,” says Williams.

In her work, Williams orders next-generation sequencing. In this type of sequencing, a target gene is read start to finish hundreds of times, and the entire sequence is reported for analysis. With so many complete reads of the gene, it is incredibly unlikely that a positive or negative result is incorrect, she says.

The 23andMe BRCA test is part of the company’s health and ancestry kit, which costs $199 and is not covered by insurance. Standard clinical genetic tests can cost $250 or less, but they are generally covered, albeit on a case-by-case basis, Williams says. And some genetic counselors and labs have started financial assistance programs for individuals who need genetic screening but would have to pay out of pocket, she says.

Since the 23andMe test doesn’t provide a clinical diagnosis, if a patient came into her office with a positive BRCA mutation result, Williams says she would order a clinical genetics test*. “We would likely recommend testing based on family history or whether they personally have had cancer,” Williams says. A consultation with a genetic counselor or even asking a primary care doctor about whether more screening would be important for you is a good place to start.

Williams doesn’t think that the existence of this test will change the standard of care for patients overall, but for some individuals it could be a new source of information to encourage them to get more screening. “I think that the availability of the test is not necessarily what will have [an] impact, as the publicity surrounding it, and just bringing awareness to people to the fact that a genetic factor could increase the risk of cancer,” Williams says.


Editor’s Note (3/19/18): This sentence has been updated to clarify that Williams would order a clinical genetic test to confirm a 23andMe variant in a patient without other risk factors. The original erroneously stated that she would not order a clinical genetic test.