The American Cancer Society has added blood tests to its colorectal cancer screening guidelines for the first time, introducing new options for patient screening.
The update reflects major advances in molecular biology, though medical authorities emphasize that colonoscopies and traditional stool tests remain the primary methods for preventing the disease.
Dr. Maria Kaparelou, a pathologist and oncologist, and Thanos Dimopoulos, professor of therapeutics, oncology and hematology, director of the Therapeutic Clinic at Alexandra Hospital and former rector of the National and Kapodistrian University of Athens (EKPA), stated that colorectal cancer remains one of the most common malignancies and a leading cause of cancer mortality.
They noted that a large percentage of cases can be prevented by identifying and removing precancerous lesions, adding that early-stage diagnosis is tied to substantially better patient outcomes. Because early detection improves survival rates, the American Cancer Society continues to advocate for regular screening.
Colorectal cancer develops in the colon or rectum, often originating as benign cellular growths known as polyps. Alexandra Hospital, located in Athens, operates as a major clinical and educational institution affiliated with EKPA, Greece's oldest public university.
FDA approvals and molecular technology
The newly included blood tests work by detecting molecular signals linked to neoplasia, including specific DNA methylation patterns and other genomic alterations. DNA methylation is a chemical modification where methyl groups attach to DNA molecules, serving as an important biomarker for early cancer development.
In 2024, the US Food and Drug Administration approved Guardant Health's Shield, marking the first blood-based test cleared for screening average-risk individuals. The federal regulatory agency followed this in July 2026 by approving Freenome's SimpleScreen, expanding the selection of approved blood tests available to clinicians.
Lower sensitivity and clinical limitations
Despite the convenience of a simple blood draw, updated clinical guidelines stress that blood tests are not currently a preferred screening method. Compared to high-sensitivity stool tests and direct imaging methods, blood tests exhibit lower sensitivity in detecting both advanced precancerous lesions and stage I cancers.
Medical experts highlight that the primary goal of screening programs is to prevent cancer from developing by finding and removing precancerous polyps early, rather than simply diagnosing an established tumor. Predictive health models also indicate that blood tests are expected to have a smaller overall impact on reducing cancer incidence and mortality across the population.
Targeting non-compliant patient groups
Due to these diagnostic limitations, the American Cancer Society places blood tests in a specific role: offered mainly to individuals who refuse or fail to complete preferred screening options. The clinical rationale rests on the principle that a less sensitive test that a patient actually completes is clinically preferable to no screening at all.
Patient compliance remains a persistent hurdle in colorectal cancer prevention programs. Colonoscopy procedures require extensive bowel preparation, patient sedation, and dedicated clinic time, which causes many individuals to delay or avoid examination.
Non-invasive stool tests, while simpler to execute, are frequently left uncompleted because patients are reluctant to collect sample specimens. Health officials hope that simple blood draws conducted during routine medical visits will lower these logistical barriers and increase participation among populations currently outside organized screening.
Follow-up colonoscopy requirements
Physicians from EKPA's Therapeutic Clinic emphasized that any positive result from a non-colonoscopy screening test, whether a blood test or a stool test, must be followed by a timely colonoscopy. Without a follow-up colonoscopy to inspect the bowel lining directly, the screening process is considered incomplete.
The updated guidelines do not replace colonoscopies with blood tests, but rather introduce an additional tool within a more personalized preventive strategy. The overarching message remains that the best screening test is one that combines high efficacy with the actual likelihood of being completed by the patient, with the ultimate goal of increasing participation and reducing colorectal cancer incidence and deaths.
