Is cancer lurking in your genes? The answer isn't always cut-and-dried.

By Roshini Rajapaksa, MD
Updated January 08, 2020
Credit: Aad Goudappel

Genetic testing can educate you about your cancer risk, but it gives you only a small piece of the picture. Here's how it works: A sample of your blood, skin cells, or saliva is sent to a laboratory that runs tests on it to look for gene mutations associated with particular conditions. (Take the BRCA gene, for example: People who carry certain BRCA mutations have an increased chance of developing breast, ovarian, or prostate cancer in their lifetimes.) The lab then sends the results to your physician, to a genetic counselor, or straight to you.

If you're interested in genetic testing for cancer-related info, you'll need to consult a genetic counselor or your health care provider first. The expert will look at your personal and family health history and help determine whether genetic testing is useful in your case. Your counselor will also help interpret the results, which aren't necessarily black-and-white. A positive test result, meaning you have a gene mutation linked to a greater risk of cancer, doesn't imply you're guaranteed to develop the cancer, just as a negative result doesn't mean you're in the clear for life. It's also worth noting that cancer is an extremely complex disease. Genetics are one of many factors at play; lifestyles components, like diet and exercise, plus smoking and alcohol habits, also matter.

You may have heard of companies that offer direct-to-consumer (DTC) gene test kits that you can use on your own. I wouldn't recommend going this route: DTC tests aren't 100 percent accurate, and results could be interpreted in different ways depending on the provider. In fact, the FDA has been cracking down on some services in recent years, pointing out the health risks posed by possible false positive or false negative results. Some of these companies have since updated their services and now offer information on ancestry and some genetic variants but not cancer risk. Others require tests involving cancer risk to be purchased through a doctor.

I suggest getting to know your family history the more straightforward way—by talking with relatives about the types of health issues (not just cancer) that run in your family, as well as when people were diagnosed. Then discuss everything you've learned with your doctor, who can advise on the most appropriate form of screening or testing for you moving forward.

Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.