Finding Cancer Sooner with a Simple Blood Test

By Dr. Graham A. Colditz, Siteman Cancer Center

It's not news that cancer screening is important. Recommended screenings can catch cancer early when it's more treatable - and some can even prevent cancer in the first place.

But not every cancer has a good screening test. In fact, screening is recommended only for breast, cervical, colon and lung cancers. While these account for a large percentage of cancers overall, it still leaves many cancers without a way to find them in earlier stages when they can be more effectively treated.

A new screening tool, called multi-cancer detection tests, may one day help fill that gap -- and in an easier, more accessible way.

"The screening tests we're most familiar with only look for one type of cancer at a time and most of those tests visualize those parts of the body," said Aimee James, a professor in the Division of Public Health Sciences at Washington University School of Medicine in St. Louis. "Multi-cancer detection tests are different because they look for more cancers at once -- and it's a simple blood test."

These new tests check for biological materials, or markers, in the blood that could indicate someone has one of the several cancers the test is designed to catch. And there is early evidence that these tests can find cancers before people notice symptoms, James said.

As positive as that is, it's just one part of the puzzle when it comes to thinking about how well screening tests work. One main question that still needs to be assessed: Do these tests lower people's chances of dying from cancer? In other words, if we find cancer through the test, will that actually translate to people living longer?

"We need more research to definitively answer that question and to determine if the benefits of these tests are worth the risks overall," James said.

It can seem counterintuitive, but all screening tests can have some level of risk. These can include physical, emotional and financial risks from follow-up testing to confirm or rule out a cancer diagnosis, or from diagnosis and treatment of a cancer that may not have become a health issue if it'd been left alone and not treated.

While these and other risks exist with other types of screening, we don't know exactly what they are with such new tools. Also, these risks may be more complex with tests that are simple to do and designed to detect many different cancers at once.

There is a lot of excitement about the potential of multi-cancer detection tests to transform cancer screening. And rightfully so. On top of possibly being able to effectively detect multiple cancers with a simple blood draw, the test may also help narrow existing gaps in cancer screening by making testing more accessible in typically underserved locations and populations with fewer health-care and screening resources.

Still, it's important to keep the enthusiasm for these new tests in sync with what we currently know about them. While some of these tests are already available through some health-care providers, they are not yet authorized by the U.S. Food and Drug Administration and aren't covered by health insurance. We're also just starting to gather information we need to fully assess these tests, such as their balance of benefits and risks -- and how we can effectively and equitably fit them within the health-care system.

"There are some promising data, but we have a lot of questions we need to answer before we can say these are definitely beneficial for everybody," James concluded.

Dr. Graham A. Colditz, associate director of prevention and control at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, is an internationally recognized leader in cancer prevention and the creator of the free prevention tool, Your Disease Risk.