Blood-based biomarker tests for colorectal cancer could soon be cleared by U.S. regulators, opening the doors to a new, more convenient way to screen for the disease, according to an April 5 Medscape article.
In March, precision oncology company Guardant Health completed its U.S. premarket approval application for its Shield blood test to screen for colorectal cancer. Companies such as CellMax Life, Freenome and Exact Sciences are also working to develop blood tests for colorectal cancer screening, according to Medscape.
"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 percent sensitivity and specificity — but turned out not to — for colorectal cancer," David F. Ransohoff, MD, a gastroenterologist at the University of North Carolina at Chapel Hill, wrote in a 2021 article.
There are a number of companies that sell multicancer-detection blood tests that include colorectal cancer screening components. However, biotech company Grail, seller of multicancer-detection blood test Galleri, and Guardant both say that their tests should be used as a supplement to colonoscopy rather than a replacement.
Though the development of blood-based biomarker tests for colorectal cancer is compelling, it is not without its flaws.
CMS is not eager to cover the tests, saying in a 2021 memo that it will only cover blood-based screening tests for certain patients that meet two standards. Firstly, the products must have received FDA market authorization with an indication for colorectal cancer screening. Secondly, they must have proven test performance characteristics for a blood-based screening test with sensitivity greater than or equal to 74 percent and specificity greater than or equal to 90 percent in the detection of colorectal cancer compared to the recognized standard as minimal threshold levels.
CMS does not currently cover Grail's blood test or the first FDA-approved blood test for colorectal cancer, Epi ProColon, according to Medscape.
For blood-based biomarker tests for colorectal cancer to become more accepted, they must secure FDA approval and Medicare coverage and receive an A or B recommendation from the United States Preventive Services Task Force, which would mandate health plan coverage, according to Medscape.
So will blood tests ever replace colonoscopy? No, at least not anytime soon. As more blood tests gain approval, they have the potential to be a great detection ally to be used alongside colonoscopy. But for now, colonoscopy remains the gold standard.