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What Genetic Tests Really Say About Your Cancer Risk

How to pick the best at-home DNA test for you — and what to do with the answers you get about your health.

By Jeanne Erdmann
Oct 24, 2020 2:00 PMOct 26, 2020 5:19 PM
young woman swabbing mouth dna - shutterstock
(Credit: B-D-S Piotr Marcinski/Shutterstock)


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Unearthing those delightful Neanderthals populating your family tree was so much fun, but now you might be ready to move on to the next step of at-home genetic testing. Maybe you’re curious about what your DNA says about your cancer risk.

You’re in good company. The at-home genetic testing market for health conditions is soaring, and the kits are more affordable than ever. The process is as simple as making a few clicks on a website, entering your credit card number, mailing your tube full of spit, and watching for the results email.

That’s the easy part. Using at-home genetic testing for health risk brings a different type of journey than discovering ancestry. But prepare yourself to collect answers you may not be ready to hear.

It’s Homework Time

First, ask yourself why you’re testing — whether you’re curious about your health risks or are worried about your family history.

Next, spend time on websites that offer direct-to-consumer cancer genetic testing. Decide whether you want answers about inherited risk for cancer only, or whether you’d like to hear about heart disease, Alzheimer’s, or how your body metabolizes medications.

If you decide to buy a kit, pay attention to how many risk genes each company includes. “Of all of the genes associated with risk for cancer, some companies might test for one or two, or just test for a handful of mutations in those one or two genes, so that would not be a comprehensive test,” says Gillian Hooker, president of the National Society of Genetic Counselors.

Results depend on which test kit you used. For instance, 23andMe spot-checks your DNA; any positive results would need to be confirmed. Other companies such as Color, Invitae, and Perkin Elmer Genomics use next-generation sequencing for a deep dive into your genes. AncestryHealth recently teamed up with Quest Diagnostics to offer such testing. If those results are positive, you can take preventive measures.

(Credit: nevodka/Shutterstock)

With at-home testing, the results come via email, rather than from a genetic counselor or your doctor. Although some companies include genetic counseling with the package, if you’re the anxious type, consider chatting with a genetic counselor before you test. The counselor can find places that cancer may be hiding in your family tree, and tailor testing to you (or, may not recommend testing at all), and help prepare you for the results.

Also know that genetic tests use databases tilted toward European ancestries, with fewer underrepresented populations and minority groups, and genetic counselors can help here, as well. Here’s where to find a genetic counselor.

Just know that a bit of worry is normal and helpful. “If your family history of cancer is strong, there’s a risk of not worrying enough,” says Hooker. “A little bit of worry may keep you moving forward to take action and reduce your risk of cancer.” But worrying so much that you take no action — or not worrying enough — is risky because there are proactive steps you can take, says Hooker.

Uh, Oh, It’s Positive

First, take a breath. Only about 10 to 15 percent of most types of cancer are due to genetic mutations passed down through families. That leaves a lot of room for environment, like whether we smoke or adhere to a healthy diet and exercise routine.

A positive result may send you down a path you weren’t expecting. But you can be proactive. If you or any family members are found to be high risk, you’ll need to consult with a genetic counselor or a genetics-savvy health care professional. You may need to take measures such as extra screening, or even preventive surgery to remove your ovaries, breasts, or your colon. “I don’t want to make this sound simple or easy, but there is significant evidence those [measures] reduce your risk of cancer,” says Hooker.

Realize, too, that genetic testing for cancer or other health conditions is all about families. Your family members — right down to aunts, uncles, and first cousins — will need to know how your test turned out. The best way to handle your curiosity about genetic testing is to tell at least your parents and siblings before you test, because results have implications for them, too, says Hooker.

Genetic counselors can help organize follow-up care for you and your family. It’s what they do, and it’s critical. “If you don’t coordinate care for the rest of your family, someone else may get diagnosed who might have been able to prevent the cancer, or detect it earlier if they had known the family had a harmful change in the genetic material,” says Suzanne Mahon, a genetic counselor and professor in internal medicine at Saint Louis University. “That’s a missed opportunity for people who need testing, and it happens all of the time.”

What Negative Means

Just as you shouldn’t immediately assume the worst if you get a positive result, don’t assume you’re automatically in the clear if your genetic test comes back negative. For example, breast cancer is common, and changes in the BRCA1 and BRCA2 genes aren’t your only risk factor. Two family members can have the condition for different reasons. Also, researchers haven’t identified all the genetic changes that cause heredity breast cancer, because some mutations are tucked away in parts of a gene that genetic tests don’t see, says Robert Nussbaum, a cancer geneticist and chief medical officer of Invitae. Bottom line: “No genetic test is 100 percent sensitive,” he says.

Realize too, that negative family histories can be misleading. “If your family history is rip-roaringly positive, that’s a strong piece of evidence,” says Nussbaum. “But negative doesn’t tell you very much; families are small, and people lose contact.”

The Future You

Having answers to your genetic cancer risk helps your future and your family’s, too. Ten years ago, women who were positive for BRCA2 mutations had the option of preventive surgery to remove their ovaries and breasts. Today, a genetic counselor will talk to you about screening for pancreatic cancer or melanoma and may also recommend more frequent screening for colon cancer, says Mahon. 

By the way, you should give a thought to your privacy. GINA, the Genetic Information Nondiscrimination Act, can protect you from employment discrimination, but you may want to buy life insurance before you test. Before you buy a kit, be sure to check out the company’s privacy policy as well as its terms and conditions notice, so you can find out what happens to your DNA sample once it’s analyzed.

Finally, the best way to approach genetic testing for cancer or any other health decision is to prepare upfront, “Make sure that you are informed and that you have the resources around you to get informed,” Mahon says.

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