CRC blood tests: A future without screening colonoscopies?


U.S. regulators may soon approve blood-based biomarker tests for colorectal cancer (CRC), expanding potential options for patients seeking more convenient forms of screening.

Most recently, Guardant Health announced the completion of its U.S. premarket approval application for its Shield blood test to screen for CRC. Approval by the Food and Drug Administration would position Guardant to later secure Medicare coverage for its test.

Rival companies, including CellMax Life, Freenome, and Exact Sciences, which already offers the stool-based Cologuard product, are pursuing similar paths in their development of blood tests for CRC.

If these companies succeed, clinicians and patients could have a choice of several FDA-approved tests in a few years.

“They’re coming, and they will be increasingly widely used,” said David A. Johnson, MD, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School, Norfolk, who earlier in his career helped win broader insurance coverage of colonoscopy.

Blood tests for CRC have the potential to cause a shift in screening for colon cancer.

Screening colonoscopies ultimately could be largely phased out in the years ahead in favor of highly sensitive noninvasive tests, if the blood tests do as well as expected, said John M. Carethers, MD, AGAF, president of the American Gastroenterological Association.

‘Holy grail?’

“A blood test for cancer screening has been the ‘holy grail’ ever since the carcinoembryonic antigen blood test in the 1960s was claimed to have nearly 100% sensitivity and specificity – but turned out not to – for colorectal cancer,” wrote David F. Ransohoff, MD, a gastroenterologist at the University of North Carolina at Chapel Hill, in a 2021 article. Dr. Ransohoff has studied noninvasive CRC screening for decades.

There is a great allure in the idea of such multi-cancer detection (MCD) tests. “MCD technology offers the potential to detect asymptomatic cancer at several organ sites with a simple blood test, often called a liquid biopsy, ” according to a National Cancer Institute FY24 budget request report.

Several companies are selling MCD tests, some of which include CRC components. Among the best-known MCD tests now sold is Grail’s Galleri. At this time, however, the Galleri test, which tests for 50 types of cancer, should be used in addition to recommended colon cancer screening tests, such as colonoscopy, the company’s website says.

Guardant has also noted that its CRC-specific blood test should only complement screening tools, including colonoscopy, not replace them.

The prospect of phasing out more commonly used CRC screening – such as colonoscopy – may be appealing, but it would require a big shift for a field in which procedures have dominated. According to a report from the Centers for Disease Control and Prevention, in 2018, 67% of U.S. adults aged 50-75 years met the U.S. Preventive Services Task Force recommendations for CRC screening, and overall, 60.6% had a colonoscopy in the past 10 years.

Still, the NCI and the FDA have signaled the potential they see in MCD tests. The NCI highlighted its plans to aid MCD test development as part of its budget request for fiscal year 2024. The NCI is preparing to launch a 4-year pilot study for MCD tests to enroll 24,000 people aged 45-70 years. The study is intended as groundwork for a randomized controlled trial that will enroll 225,000 people.

The FDA has shown an interest in helping companies bring blood tests for cancer detection to market through its breakthrough device designation – a sign that the FDA places great priority on a product and seeks to streamline the application and review process.

CellMax Life appears to be the only CRC-specific screening blood test to have received a breakthrough device designation from the FDA, Atul Sharan, MS, MBA, cofounder and chief executive officer of CellMax Life, said in an email.

Lance Baldo, MD, Freenome’s chief medical officer, said in an interview that the FDA may be reviewing parts of their application in 2024, allowing for a potential 2025 launch of a blood test for asymptomatic people at average risk for CRC.


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