Are Multitumor Blood Tests More Hype Than Help?

Event Transcript

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Summary and Key Highlights

By Kara Grant

Are multitumor blood tests more hype than help? That's the question at the heart of the most recent Medscape Masters roundtable. The discussion was moderated by Phillip Castle, PhD, MPH, director of the Division of Cancer Prevention at National Cancer Institute. He was joined by Elizabeth O'Donnell, MD, director of Early Detection and Prevention at Dana-Farber Cancer Institute, and assistant professor at Harvard Medical School; Chyke Doubeni, MD, MPH, chief health equity officer for The Ohio State University Wexner Medical Center, and associate director for diversity, equity and inclusion at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute; and Tomasz Beer, MD, chief medical officer, multi-cancer early detection, at Exact Sciences, and adjunct professor of medicine at Oregon Health & Science University.

What We Know and Don't Know

The multicancer early detection (MCED) tests at the center of this conversation use molecular profiling to detect multiple cancer signatures in blood. This is a huge development, especially for lethal cancers, like ovarian and pancreatic cancer, that don't have sufficient screening measures.

As of now, there's still a lot we don't yet know about these tests and their capabilities, including their sensitivity, specificity, and their ability to detect how far along the cancer is. Castle noted that there are more than 50 tests in various stages of development, and their performance differs significantly by the organ or tissue type and the severity of the cancer.

"You're mixing information about different cancers at different stages," O'Donnell said. "It becomes a hard analysis to do when you think about how you approve these [tests], and how you recommend their use."

Ultimately, the goal of these tests is to get to a point where rare and lethal cancers can be detected early on, with the hopes of avoiding complex, expensive, and sometimes toxic treatments for cancers that are more advanced.

False-Positives and Overdiagnoses

Although we still have a ways to go, these multicancer tests are being designed to have high levels of specificity.

"When you think about the false-positive rates for current, accepted single-cancer screening tests, they tend to be around 10%-11%," Beer said. "Here, we're looking at 1% or so."

That's because the consequences of a false-positive test that can detect many different cancers are much more complex than a false-positive test for a single cancer for which the diagnostic journey is "well-worn and well-understood." said Beer.

The Galleri test, a multicancer test that is currently in circulation but is not yet approved by the US Food and Drug Administration, poses a challenge for primary care physicians like Doubeni. The evidence of the test's efficacy is promising but still immature.

Beer wants physicians to know the numbers: About 1% who undergo the testing will have a positive result, and of those who have a positive result, about 2 out of 5 end up with a cancer diagnosis.

A Path Forward for Health Equity?

This testing is designed to make early cancer detection more widely available and accessible to people who may not receive consistent healthcare. Although the widespread availability of this testing can save lives, it may not be able to solve all our cancer-related healthcare disparities. It might even exacerbate them, said Doubeni.

"I don't think that we should hang our hopes on the fact that if MCED tests were available today, it would solve the equity problem," Doubeni said. The cost of the tests, trust in the healthcare system, and limited access will still be barriers to testing regardless of whether they are widely available.

Beer said that it is a high priority to get the high costs of the tests reimbursed — and getting FDA approval is a key step to doing that. It doesn't guarantee reimbursement, but it's a step in the right direction.

Watch the full recording of the event above.

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