What Can Genes Tell Me About My Cancer Risk?

Before pursuing any kind of genetic testing, it is important to understand that the majority of cancers are not the direct result of genes passed down from your parents. Inherited gene changes sometimes called mutations or variants contribute to somewhere between 5 and 10 percent of all cancers. For that reason, genetic testing and counseling is typically recommended only for people who have had certain types of inherited cancer or who have histories of cancer within their family.

Genetic testing allows healthcare providers to look for inherited gene mutations associated with increased cancer risk, such as BRCA1 and BRCA2 gene changes that have a clear tie to breast and ovarian cancer. For example, women in the general population have roughly a 12 percent chance of developing breast cancer in their lifetime; for women with BRCA mutations, it is closer to 70 percent, according to the NCI. Understanding that risk can help a woman and her healthcare providers plan prevention strategies.

RELATED: My Genetic Test Came Back BRCA Positive. Now What?

Medical-grade genetic cancer testing is typically ordered by your doctor or a specialist, such as a genetic counselor. The tests are noninvasive and typically use a blood or saliva sample.

"Medical-grade testing is developed and approved to answer medical questions [such as]: 'Do I carry a mutation in one of these hereditary cancer genes?'" says Ellen Matloff, the president and CEO of My Gene Counsel, a company that helps clients better understand their genetic testing results, and the former director of the cancer genetic counseling program at Yale University School of Medicine in New Haven, Connecticut. "At-home testing kits are for entertainment and are not developed, or approved, to answer medical questions."

There are several reasons for that. Medical-grade testing is far more thorough, Matloff says. For example, medical-grade testing for BRCA gene mutations analyzes thousands of gene variant options, whereas one leading at-home kit considers just three.

There are also differences in accuracy. A study published in March 2018 in the journal Genetics in Medicine found that 40 percent of gene variants reported in direct-to-consumer tests were false positives and that some of the variants companies told users meant they were at increased risk for certain health conditions are actually considered common gene variants by clinical labs.

An unpublishedstudy presented in October 2019 by Invitae, a medical-grade genetic testing company, found that an individual's ethnicity may have a significant impact on whether their at-home test results are accurate. MUTYH gene mutations, for example, would have been missed in 100 percent of Asian and 75 percent of African American test takers, but only 33 percent of Caucasian individuals.

"Medical-grade testing uses laboratory techniques and validation methods not used by most at-home testing kits," Matloff explains. "So those results are generally more accurate."

Health insurance plans will often cover genetic testing which can cost thousands of dollars but not always, according to the U.S. National Library of Medicine and Breastcancer.org. Direct-to-consumer genetic cancer risk tests tend to be less expensive, so they can be a good starting point for people who are worried about their family history and who do not want to spend too much.

"There are some at-home genetic cancer testing kits that are good, reasonably priced, and convenient for people who do not meet insurance criteria for coverage of traditional medical-grade testing and prefer to pay out of pocket and have the test delivered to their house," Matloff says.

But it is important to remember that everyone from the American Cancer Society to the U.S. Food and Drug Administration (FDA) caution that the tests may provide incomplete or inaccurate information, and urge individuals to talk to their doctors before making any health-related decisions on the basis of those tests.

Read more:
What to Know Before You Buy an At-Home Genetic Cancer Risk Test - Everyday Health

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