A spotty track record
Before anyone gets too excited about the prospect of phasing out screening colonoscopy, it’s important to remember that CRC blood tests have proven disappointing in the past.
Germany’s Epigenomics, for example, secured the first FDA approval for a CRC blood test, Epi ProColon, in 2016. But the company did not receive Medicare coverage for the test. In a 2021 memo explaining the decision, the Centers for Medicare & Medicaid Services noted that, given more reliable alternatives, including stool-based tests, the Epi ProColon would result in harm to some patients.
CMS also does not cover Grail’s blood test, which has a list price of $949, though the company has secured reimbursement arrangements with several self-insured employers and insurers, such as Point32Health.
But CMS officials have acknowledged the strong interest in CRC blood tests.
In that 2021 memo, the agency also outlined its requirements for Medicare coverage. CMS said it will cover blood-based screening tests for certain patients if these products meet the following standards:
- Receive FDA market authorization with an indication for CRC screening.
- Have proven test performance characteristics for a blood-based screening test with sensitivity of at least 74% and specificity of at least 90% in the detection of CRC, compared with the recognized standard (which at this time is colonoscopy) as minimal threshold levels, based on the pivotal studies included in the FDA labeling.
In February 2023, CellLife Max presented data at ASCO Gastrointestinal Cancers Symposium that its blood test had sensitivity of 92.1% for detection of CRC and 54.5% for detection of advanced adenomas, at 91% specificity.
Prior to that, in December 2022, Guardant issued a press release with study results that met the CMS standard. The test had sensitivity of 83% in detecting individuals with CRC. Specificity was 90%, the company said. That translates to a false positive rate of just 10%.
While such results look promising, Asad Umar, DVM, PhD, the chief of gastrointestinal and other cancers at NCI’s division of cancer prevention, said physicians should be cautious when giving advice or answering questions about MCD tests, given limited data from prospective studies about their effect on health outcomes.
Even among physicians already using some MCD tests to screen patients, there is a lot of concern about false-positive results that require diagnostic workup and false negative results that lead to a false sense of assurance, Dr. Umar said.
“Screening is a process and not just a test. The process involves follow-up testing for any positive test findings,” Dr. Umar said. “At this point, doctors should inform patients that there is not sufficient data to know how best to use these tests.”
Hurdles to broad acceptance
For companies seeking broad acceptance of a CRC blood test, two of the three major steps needed are securing FDA approval and Medicare coverage. The last step would be getting an A or B recommendation from the USPSTF, which would mandate coverage by health plans.
This is the “big trifecta,” Dr. Baldo said.
In the USPSTF’s current colon cancer screening recommendations, issued in 2021, it gave an A grade for CRC screening for adults aged 50-75 years and a B grade for those aged 45-49 years.
The USPSTF’s recommended forms of screening include colonoscopy, high-sensitivity guaiac fecal occult blood (gFOBT), fecal immunochemical test (FIT), flexible sigmoidoscopy (FS), stool DNA, and/or computed tomographic colonography (CTC).
The USPSTF says more research is needed to establish the accuracy and effectiveness of emerging screening technologies, such as blood or serum tests.
If CRC blood tests eventually win FDA approval, the USPSTF would likely provide guidance to clinicians on how patients can use them as a screening option.
Dr. Ransohoff noted that the mission of the USPSTF is different from that of the FDA and CMS. The FDA’s approach on medical tests is to consider overall safety and efficacy, as does CMS, but neither agency makes recommendations, nor does it perform its own rigorous quantitative assessment of benefit versus harm. The USPSTF, however, does its own detailed evidence-based reviews of the benefit versus harm of products, Dr. Ransohoff said.
“To me, the Task Force is the gold standard,” Dr. Ransohoff said. “You have to jump through the hoops with the FDA and CMS for making claims, to enable use, and to help get payment. But the Task Force looks at the choices and the consequences in a quantitative way and makes specific practice recommendations.”