Why 23andMe may not detect your risk of breast cancer

Read Advisory Board's take: How providers should respond to this news

A study of 100,000 people released earlier this month shows that nearly 90% of women who carry a BRCA mutation which increases their likelihood of cancer would have been missed by 23andMe's genetic test, Heather Murphy reports for the New York Times.

23andMe's website states that its BRCA1 and BRCA2 test focuses on three types of gene mutations, known as founder mutations, that are known to increase the likelihood of cancer and commonly occur among Ashkenazi Jews, Murphy reports. Jeffrey Pollard, 23andMe's director of medical affairs, explained, "We test for these three variants since they are three of the most well-studied and carry clear, documented risk for breast and ovarian cancer," he said. "About one in 40 individuals of Ashkenazi Jewish descent has one of these three variants. Women with one of these variants have a 45 to 85% chance of developing breast cancer by age 70."

However, a new study suggests that there are numerous other genetic variants that increase the risk of breast cancer that 23andMe does not test for and would not catch.

Study details

The study, which was conducted by another diagnostic company Invitae, and has not been peer-reviewed, examined data on over 100,000 patients who took Invitae's breast cancer gene test.

The study found that almost 90% of participants carried a BRCA mutation that would have been missed by 23andMe's test. Among the Ashkenazi Jews in the study, 81% carried one of the BRCA mutations that 23andMe looks for, suggesting that the test could detect their increased risk. However, 94% of the remaining participants carried a mutation that would not be detected by 23andMe's tests.

The researchers recently presented their findings at the American College of Medical Genetics and Genomics annual meeting.

Susan Klugman, VP for clinical genetics at the American College of Medical Genetics and Genomics, who was not involved in the study, compared the differences in the tests to a spell check: While Invitae's broader analysis looked for errors in the entire story, 23andMe's test looks in just a few paragraphs.

According to Murphy, if only a fraction of 23andMe's more than 10 million customers took the test, "thousands … could be misled" about their risk.

Experts divided on impact of 23andMe's narrow test results

Mary-Claire King, a professor at the University of Washington, criticized 23andMe's test and FDA's approval of the test. She said, "Misleading, falsely reassuring results from their incomplete testing can cost women's lives," adding, "FDA should not have permitted this out-of-date approach to be used for medical purposes."

Pamela Munster, the co-leader of the Center for BRCA Research at the University of California, San Francisco, is among those who received a negative 23andMe test only to later learn, when she was diagnosed with breast cancer, that she did indeed carry the mutation. Munster, who was not involved in the study, compared 23andMe's BRCA test to a pregnancy test that would show a positive reading only for Jewish women.

But while she said she's concerned customers may not fully understand the limits of the test, she didn't believe 23andMe is "doing anything actively deceptive" since it does clearly state on its website that it is only testing a limited number of BRCA mutations.

Robert Green, a professor at Harvard Medical School, similarly said 23andMe's limitation isn't necessarily a problem, and that the responsibility is on the customers to be aware of the limitations of the direct-to-consumer test. "I think people have the right to their own genetic information, but with that right comes a responsibility," he said. "If you are going to go around the medical mainstream, read the caveats."

Regardless, it's a good idea to talk to a genetic counselor or a medical geneticist after taking a DNA test, according to Klugman. These counselors can help patients understand their test results and potentially discover incorrect findings, she said (Murphy, New York Times, 4/16).

Advisory Board's take

Deirdre Saulet, Practice Manager, Oncology Roundtable

This study validates the concerns that many in the field voiced when the FDA authorized 23andMe's BRCA test. While 23andMe believes they are "clearly" stating the limitations of the test, it comes as no surprise that this caveat is lost amid the complexity and emotional nature of cancer risk assessment—a topic that's confusing for patients and providers alike.

Unfortunately, this isn't the only problem of its kind. Earlier this year, the FDA approved 23andMe's direct-to-consumer test for an increased risk of colorectal cancer. Similar to the breast cancer test, this has serious limitations in that it only tests for two genetic changes indicating a hereditary condition. It does not test for the many other variants or syndromes, such as Lynch Syndrome, which can lead to increased risk of colorectal cancer. 

“Genetic counseling programs need to develop a proactive strategy to share education and clarifying information ”

In response, genetic counseling programs need to develop a proactive strategy to share education and clarifying information about the limitations of the 23andMe risk assessment tests. In particular, they should aim to help providers and patients understand that testing negative on these tests is not a complete picture of hereditary risk.

Furthermore, while consumers may feel like they're prepared for this information, those that learn that they're at a higher risk of developing cancer will undoubtedly face anxiety and stress. While 23andMe says it encourages customers who test positive to follow up with a clinician, there are concerns that providers won't be prepared to speak to the results or will have reservations about the findings. Organizations should create processes to connect these patients with genetic counseling to help them understand their genetic information, family history, further testing alternatives, and, if necessary, options for prophylactic treatment.     

The value of genetic counselors, who can make sense of these various tests and results, is certainly highlighted by this article. But counselors are already in short supply. Learn how Sharp Healthcare is improving access to genetic counseling in this blog. Then, to learn more about how to develop a best-in-class cancer genetic counseling program, view our on-demand webconference and download our slides here.

Read the Blog Download the Slides

What providers need to know about genetic testing

In 2017, nearly 1 in 25 Americans had access to their genetic data—and many are showing up to their annual wellness visit looking for answers to their genetic test results. Some projections suggest that the direct-to-consumer genetic testing market will triple by 2022.

Here's a roundup of our blog posts, insights, and research on the topic so your organization can take the best approach to this technology.


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