What home DNA kits can (and can't) tell you about cancer risk

It's hard to miss the barrage of clever advertising for home DNA tests — and the marketing works. Home DNA tests were among the top 10 holiday season gifts ordered on Amazon in 2018.

 

When they first came along about a decade ago, home DNA tests were offered as a glorified form of entertainment that cranked out tidbits of information people could share at parties. But DNA analysis can tell us much more, including our risk of developing some cancers and other diseases.

 

One popular company, for example, provides a growing range of health-related genetic information to its customers, ranging from increased risk for breast cancer, Alzheimer's and Parkinson's disease, to whether a person is a carrier for dozens of inherited conditions like cystic fibrosis and sickle cell anemia.

 

It's reasonable to assume that other companies will follow this path, and with more players in the market, it will likely become easier and cheaper than ever to ship out your saliva sample in a postpaid envelope and get back a slew of reports dissecting what your DNA says about your present and future health. So, should you?

“This is a hotbed issue,” said City of Hope's Kathleen R. Blazer, Ed.D., M.S., L.C.G.C., a board-certified genetic counselor and educator. Blazer and her colleagues worry that customers will make incorrect assumptions about the breadth and accuracy of home tests, that they may substitute a home kit for a more complete and informative screening at a qualified medical center, and even make questionable medical decisions based on the limited information they receive.

 

If you've thought about trying one of those home kits, Blazer urges you to think before you spit. Even the most elaborate home test, she asserts, only scratches the surface.

 

“This is recreational genetics. It's very superficial, a very limited screening, not at all a thorough analysis,” she said. Unlike a full screening performed by a geneticist, which reads a patient's DNA and detects and analyzes crucial genetic alterations, home tests are extremely limited. For the most part, they examine only a small fraction of total DNA, relying on “surrogate” criteria such as single nucleotide polymorphisms or SNPs, some of which, when compared to SNPs in the larger population, may indicate a statistically elevated risk.

 

People get their test results and jump to conclusions, either assuming everything's fine, or believing they're at high risk for a disease, which may not be the case. Some will take their test reports to a doctor, who may be just as much in the dark as the patient.

Blazer and her colleagues in the Division of Clinical Cancer Genomics are laboring to correct that. As director of City of Hope’s Cancer Genomics Education Program, she helps oversee a multifaceted cancer genetics education initiative. The program aims to give clinicians — doctors, physician assistants, nurses, genetic counselors and others — the tools and information they need to take better care of their patients. More than 1,000 medical professionals in all 50 states and 25 countries have successfully completed the program, with another 1,200 currently enrolled.

 

At the same time, Blazer says testing companies need to do a better job of informing their customers.

 

“Testing companies must provide black-letter warnings that are very clear and hard to miss,” she said. Blazer wants companies to offer more comprehensive resources — like guidance on where to find a qualified geneticist in your local area to receive a complete screening. “This is important for folks who take a DTC test and have it come back positive, but it can also be very important for those with a negative result who assume they’re not at risk. This is especially critical if they have red flags for risk, like a personal history of cancer, or cancers in their family history.”

 

The industry is listening. Blazer chairs a direct-to-consumer working group at the National Human Genome Research Institute (part of the National Institutes of Health) that's examining existing DTC information resources, and working with testing companies to improve and upgrade their offerings. Those efforts appear to be having an effect: testing companies are adding more information to their websites and placing it more prominently.

 

But customers still have to read it. And once they get their test results, the next step is even more critical.

Some home tests may indicate you have a mutation associated with Alzheimer's,” said Blazer, citing one example. “But it may not necessarily mean you're at high risk for the disease. There are other genetic factors involved in assessing that risk ... and those factors are not measured in a home test.” hat's why it's so important to follow up with testing and counseling from a health care professional who is specifically trained to administer a medically approved test and accurately interpret the results.

 

Why then bother with a home test at all? Blazer does see some benefit: DNA information is entering more people’s comfort zones.

 

Not that long ago, patients would have their DNA tested anonymously, fearing discrimination in the workplace or by insurance companies if a high risk of disease were detected. The law changed in 2008, making such discrimination illegal.

 

“The popularity of home testing is helping to build awareness, understanding and comfort in the whole area of genetic information,” Blazer said. “It's challenging the concept of exceptionalism about genetics, combating the fear of discrimination based on your DNA ... and it's bringing down the cost.”

 

When more people gain more knowledge, Blazer said, it could ultimately save lives.

 

“I'm seeing people come forward,” she said, “once they find out what they didn't know. Folks who took the test for fun, and discovered a possible risk to their health.”

 

Just be sure to underline that word possible.

 

“Remember,” Blazer emphasizes, “A screening is not a diagnosis. Never take any medical action [based on a home test] without confirming the results first. The important thing to remember with direct-to-consumer tests is to get your results confirmed with a professional genetics consult.”

 

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