On Mar. 13, 2024, the Fred Hutchinson Cancer Center announced that a blood test intended for screening for colorectal cancer in people who are of average risk and not experiencing symptoms correctly detected colorectal cancer in 83% of people confirmed to have the disease. The study was published in the New England Journal of Medicine.

The Shield test detects colorectal cancer signals in the blood from DNA that is shed by tumors, which is called circulating tumor DNA (ctDNA). ctDNA is also being used in “liquid biopsy” tests used for monitoring for cancer recurrence in people who have been treated for cancer and for other emerging cancer screening tests.

Of the 7,861 people included in the NEJM report, 83.1% of the participants with colorectal cancer confirmed by colonoscopy had a positive blood test for ctDNA and 16.9% had a negative test — in which a colonoscopy showed colorectal cancer but the ctDNA test did not. The test was most sensitive for colorectal cancers, including early stage cancers, and was less sensitive for advanced precancerous lesions, which can turn into cancer over time.

The accuracy rate for colorectal cancer is similar to at-home stool tests used for early detection of colorectal cancer. The findings come from the ECLIPSE study, a multisite clinical trial of nearly 8,000 people ages 45 to 84 led and funded by Guardant Health.

According to the American Cancer Society, colorectal cancer is the second most common cause of cancer deaths in adults in the U.S. and is expected to account for 53,010 deaths in 2024. While death rates from colorectal cancer in older adults has declined, rates among those under age 55 have increased by about 1% a year since the mid-2000s. Current guidelines advise that people of average risk for colorectal cancer begin regular screening at age 45.