The American Cancer Society has revised its colorectal cancer screening guidelines to include a new blood-based test as an additional option for adults aged 45 and older. The updated recommendations, released on Wednesday, aim to increase screening rates among eligible individuals by offering more accessible methods beyond the traditional colonoscopy and stool-based testing.

Colorectal cancer remains the third most commonly diagnosed cancer in the United States, with an estimated 160,000 new cases and 55,000 deaths annually. It is also the leading cause of cancer-related mortality in adults under 50. Early detection is crucial, as colorectal cancer is often preventable and highly treatable when identified in its initial stages. However, approximately one-third of those recommended to undergo screening are currently not up to date.

The newly incorporated test, known as Shield, detects fragments of tumor DNA in the bloodstream and received regulatory approval in 2024. Developed by Guardant Health, Shield offers a simpler and less invasive alternative to colonoscopy and stool-based screening. Nonetheless, the test has significant limitations, particularly in its reduced sensitivity in detecting precancerous polyps and stage 1 cancers compared to established screening methods.

According to the guidelines published in CA: A Cancer Journal for Clinicians, Shield is recommended solely for individuals who are unwilling or unable to undergo standard screening tests. Colonoscopy remains the preferred screening tool, recommended every 10 years from age 45 through 75, while stool-based tests, which identify blood or genetic markers linked to colorectal cancer, continue to serve as another standard option.

Experts emphasize the importance of screening completion over the choice of test. William Dahut, chief scientific officer of the American Cancer Society, noted that while the blood test may not be as effective in detecting early-stage disease, it could still benefit patients who would otherwise forgo screening altogether.

Data from a large clinical trial published in The New England Journal of Medicine showed that the Shield test detected 83% of colorectal cancer cases but identified only 13% of advanced precancerous lesions. This disparity underscores the need for careful patient-provider discussions about the relative benefits and drawbacks of each screening option.

Matt Kalady, director of the James Colorectal Cancer Center at Ohio State University Comprehensive Cancer Center, described the addition of a blood test as a positive development but cautioned it should be reserved for patients declining other tests due to its lower efficacy. Similarly, Scott Ramsey, a cancer researcher at the Fred Hutchinson Cancer Center, welcomed the broader screening options but expressed concern that the test’s limitations might complicate clinical conversations.

While the American Cancer Society’s guidelines are widely influential, they do not directly impact insurance coverage. Coverage decisions in the United States typically rely on recommendations from the U.S. Preventive Services Task Force, which currently does not endorse blood-based colorectal cancer screening tests. As a result, the integration of Shield into routine screening protocols will depend on ongoing evaluations of its effectiveness and uptake in clinical practice.