The United States Food and Drug Administration (FDA) recently approved a new colorectal cancer (CRC) blood test for screening those at average risk of cancer. It adds to the suite of options people have for CRC screening, but people should also be aware of the limitations of this new test.

CRC is the second leading cause of cancer death in the United States today. Fortunately, screening with colonoscopy or sigmoidoscopy, fecal immunochemical test (FIT) has been demonstrated to reduce the incidence and mortality from colorectal cancer.

CRC screening is recommended for average risk adults starting at age 45. Unfortunately, only 72.2% of US adults were up to date with CRC screening in 2021.  The rising incidence of CRC in younger adults compounds the need to increase screening participation.

The newly approved blood test for CRC screening may be attractive to individuals who would rather not undergo a colonoscopy or collect a stool sample. However, there are serious limitations to the test. Particularly significant, the new blood test misses 87% of advanced pre-cancerous lesions. Comparatively, FIT, a less expensive alternative, detects about 24% of advanced precancerous lesions, while colonoscopy detects more than 90% of advanced precancerous lesions.

“Not all screening tests are equal, but getting people to screen for colorectal cancer is critical in saving lives. The blood-based test could help reduce cancer deaths if individuals who refuse the proven screening tests are willing to be screened with the blood test. However, those with a positive/abnormal blood test would still need to be willing to undergo colonoscopy to achieve any benefits of screening,” said Prateek Sharma, MD, FASGE, ASGE’s President. “The blood test, in and of itself, is not helpful without a follow-up colonoscopy,” he added. At this time, insurance does not cover this test.

Those at increased CRC risk (e.g., due to family history of cancer or advanced colorectal polyps, irritable bowel disease (IBD), or certain genetic syndromes) should talk to their doctor about which CRC test is right for them. Those with symptoms of CRC (e.g., blood in the stool) or iron deficiency anemia should not have a screening test, rather they should talk to their doctor about a diagnostic colonoscopy.

“Though the blood test is FDA approved, it may be some time before organizations such as the US Preventive Services Task Force (USPSTF) make recommendations about this test,” said Jason Dominitz, MD, MHS, MASGE, ASGE’s Vice President. “What is important to note is that not all tests have the same level of effectiveness and outcomes. ASGE and other national organizations recognize colonoscopy as the optimal colorectal cancer screening tool due to its unique ability to detect and remove polyps in one setting.”

 It is important to clarify and educate clinicians on the importance of sequential offers of screening tests. In particular, the availability of the new blood test should be accompanied by recommendations for colonoscopy and the currently available fecal tests first, reserving the blood test for patients who decline colonoscopy and fecal testing as well as understand the limitations of the test.

See ASGE’s current recommendations on colorectal cancer screening and download an easy-to-use infographic.