Study: Blood test detects colorectal cancer but misses most precancerous polyps

Editor's Note

A new blood test shows promise in detecting colorectal cancer—the second leading cause of cancer deaths in the US—but was less effective at identifying precancerous polyps, according to a June 2 announcement from Kaiser Permanente. Not yet approved by the US Food and Drug Administration, the test is designed to detect circulating genetic material shed by tumors and, potentially, precancerous growths.

Published in JAMA, the study enrolled 27,010 adults aged 45 to 85 who were at average risk for colorectal cancer. Participants joined the study between May 2020 and April 2022 at 201 U.S. sites, including Kaiser Permanente Northern California, and underwent a colonoscopy within 120 days of providing a blood sample for testing. The test was evaluated based on its ability to detect findings later confirmed during colonoscopy. 

According to the announcement, the test correctly identified colorectal cancer in 79.2% of participants with tumors detected by colonoscopy. This included 16 of 28 with stage I, all 15 with stage II, 14 of 17 with stage III, and all 11 with stage IV cancer. The test also correctly ruled out disease in 91.5% of participants who had neither cancer nor advanced precancerous lesions.

However, the test detected only 12.5% (321 of 2,567) of participants who had advanced precancerous polyps identified and removed during their colonoscopy. As noted in the announcement, removing these polyps is key to cancer prevention, and current tests such as colonoscopy and stool testing remain more effective. The researchers note that further studies are needed to improve the new test’s ability to detect precancerous polyps and to evaluate whether it reduces cancer incidence and death.

In addition to further details on the study, the full article offers numerous statistics on colorectal cancer, screening rates, and the promise of new tests for reducing barriers.