Experts are concerned about the test's limitations.

By Julia Malacoff
March 14, 2018
Photo: Victor Moussa/Shutterstock

You've probably heard about the genetic tests for hereditary breast cancer. They look for genetic mutations called BRCA1 and BRCA2, which increase a person's risk of breast, ovarian, and/or prostate cancer. While only a small portion of breast cancers overall are due to inherited genes, women with BRCA1 or BRCA2 mutations are significantly more likely to develop breast cancer during their lifetimes.

"The average woman in the United States has about a 1 in 8, or about 12 percent, risk of developing breast cancer," says Tinamarie Bauman, a board-certified advanced genetic nurse and assistant director of the High Risk Genetics Program at AMITA Health Cancer Institute. "Women who have a BRCA1 or BRCA2 mutation (or both) can have up to an 80 percent risk of being diagnosed with breast cancer." What's more, breast cancers associated with these genes tend to develop in younger women and occur more often in both breasts than cancers in women without these abnormal genes, she says.

For these reasons, genetic testing can play an integral role in breast cancer prevention and treatment for some women. Generally, these tests are only accessible to those who have met with a genetic counselor, who can help them decide whether testing is an appropriate choice for them based on their personal and family history of breast cancer. Though some companies offered this test for people to do from the comfort of their own homes, doctors needed to order them for you-until now.

The U.S. Food & Drug Administration announced that they're granting approval to 23andMe's direct-to-consumer BRCA test (after previously asking them to stop providing the test back in 2013). The test helps people determine whether they have certain BRCA1 or 2 mutations. But experts are already cautioning that just because something is FDA-approved doesn't necessarily mean it's a good idea for everyone to take the test. Here's why.

What the FDA Approval Actually Means

"The best way to think about this test is like any other screening test, like a mammography, colonoscopy, or Pap smear," says Robert Maganini, M.D., director of St. Alexius Breast Care Center near Chicago. "This is a screening test for three specific BRCA gene mutations, which are associated with a much higher risk of developing breast cancer, particularly at younger ages, and ovarian cancer." But like any other screening test, this one has both pros and cons, he says.

One of the main reasons the test was approved for use is that 23andMe was able to prove that it was able to accurately identify the three specific mutations the test searches for. But the FDA still cautions that the test has limitations. First, they recommend confirmatory testing after a positive result, because while the test is relatively accurate, it doesn't use the most accurate testing techniques.

Plus, the fact that it only tests for three mutations is pretty limiting. "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," Donald St. Pierre, acting director of the Office of In Vitro Diagnostics and Radiological Health in the FDA's Center for Devices and Radiological Health, said in the FDA's press release.

The chance of finding one of these three BRCA mutations, also known as the BRCA founder mutations, in the general population is less than 1 percent, and is only 2 percent within the Ashkenazi Jewish population, where they are most prevalent, according to a National Cancer Institute study. "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," St. Pierre adds.

Why Experts Are Worried

Yes, the test looks for three of the riskiest BRCA mutations, but research shows that there are at least 65 more variants that increase the risk of breast cancer. While none of these have been shown to boost risk of breast cancer as much as the mutations the 23andMe test looks for, it's still very possible to receive a negative result on the 23andMe test and have an elevated risk of breast cancer due to genetics-especially if you're not Ashkenazi Jewish.

The mutations the 23andMe test looks for primarily occur within one very specific population: Ashkenazi Jews. "This test is not useful outside of the Ashkenazi Jewish population," Bauman says. That's because the three mutations it looks for are also known as the BRCA founder mutations. "A founder mutation is a specific gene mutation in a population that was founded by a small group of ancestors that were geographically or culturally isolated," Bauman says. "Because the population was isolated, the rate of founder mutations in descendants is much higher than it would be if the population was larger and comingling with more genetically diverse people." In the case of the BRCA1 and 2 mutations the 23andMe test looks for, the founder mutations come from the Ashkenazi Jewish community, and these mutations are part of the reason women of Ashkenazi Jewish heritage are at a higher risk for breast cancer.

Part of the problem, though, is that even though 23andMe is quite clear about the fact that the test is mainly useful for those with this specific heritage, not everyone is reading the fine print. "I've already seen many of my non-Ashkenazi friends all over social media talking about how they can now get tested 'for breast cancer' through a direct-to-consumer lab," Bauman says. "I can already imagine patients who actually need testing telling their physicians that they 'already had BRCA testing' and their physicians just taking it at face value," she says.

That said, for Ashkenazi Jewish families without a history of these cancers, this test could be a way to find out about unexpected genetic risk. "One in 40 Ashkenazi Jews-men and women-carries a BRCA gene mutation, more than 10 times the rate of the general population," Bauman explains.

But here's the thing: "Different ethnic and geographical regions have different BRCA1 and BRCA2 mutation spectra and prevalence," Bauman says. That means if you're not Ashkenazi Jewish, your community may have its own BRCA mutations to look out for, making this particular test pretty much irrelevant to you.

The Bottom Line On BRCA Testing

If you have Ashkenazi Jewish heritage (or think you might), and no history of breast, ovarian, or prostate cancer in your family that would send you to a genetic counselor, then this test could be a good option for you if you want to learn more about your cancer risk.

Otherwise, it's probably better to skip it. BRCA and other hereditary cancer genetic testing is an important part of cancer prevention, Dr. Maganini says, but genetic testing is of very limited value as 90 percent of most cancers are unrelated to known mutations. That means unless you're part of a population that is likely to have high-risk genetic variants, lifestyle factors are likely more important than getting genetic testing when it comes to cancer prevention.

"Rather than taking this test, I would recommend people be proactively vigilant about understanding their cancer risk through careful discussions with their primary care physician," Dr. Maganini says. "Additionally, lifestyle modification, typically through better nutrition and increased activity, is the most important strategy to reduce the risk of most cancers." Not sure how to get started? Here's what really works to lower your breast cancer risk.


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