• Posted June 13, 2025

CT Scans Outperform DNA Stool Tests In Colon Cancer Screening, Study Says

FRIDAY, June 13, 2025 (HealthDay News) —  CT scans might be able to prevent more colon cancers than stool DNA tests, a new study says.

CT colonography performed every three to five years could ward off more cases of cancer than DNA testing of stool to look for evidence of colon cancer, researchers reported June 10 in the journal Radiology.

“Among the safe, minimally invasive colorectal cancer screening options, CT colonography is more effective at preventing and detecting cancer — and is also more cost-effective — than stool DNA testing,” lead researcher Dr. Perry Pickhardt said in a news release. He's a professor of radiology and medical physics at the University of Wisconsin School of Medicine and Public Health.

Colonoscopy remains the dominant form of colon cancer screening, Pickhardt noted. The procedure, while invasive, remains the gold standard for screening because pre-cancerous polyps can be removed during the exam.

However, many patients opt for either stool tests or CT scans because they are uncomfortable with a colonoscopy, which requires a person to be sedated while a thin, flexible tube is inserted into their colon through the anus.

Medicare now covers both DNA stool testing and CT colonography, so researchers decided to perform a head-to-head comparison of the two less invasive screening methods.

DNA stool tests search for genetic evidence of colon cancer in samples taken from patients, while CT colonography uses CT scans to examine the colon and rectum.

For the study, researchers created a model to simulate the progression of colon cancer, and how the different screening methods might detect and prevent cancers. The model was based on 2017 data from the U.S. Centers for Disease Control and Prevention (CDC).

Screening of the simulated population began at 45 years old and ended at 75, researchers said.

Without any screening, researchers estimated that just under 8% of people would develop colon cancer and 3% would die from it each year.

Results show that colon cancer cases would decline by an estimated 59% with stool DNA tests performed every three years.

But two different approaches of CT colonography would prevent even more cancer cases, researchers estimate:

• A 70% reduction with CT scans performed every three years and follow-up colonoscopy performed to remove polyps 10 millimeters or larger.

• A 75% reduction with CT scans every five years and follow-up removal of polyps 6 millimeters or larger.

These results indicate that CT colonography can join conventional colonoscopy and stool testing “as a legitimate frontline screening option,” researchers concluded.

“In particular, CT colonography may represent a highly favorable screening strategy for younger patients” in their 40s, researchers noted.

Both CT scan strategies were also more cost-effective than stool DNA testing, researchers said.

However, the five-year CT strategy was not as cost-effective as the three-year strategy, the study says.

People who undergo CT colonography still have to perform bowel prep, using powerful laxatives to empty their colon prior to the exam.

But Prickhardt noted that a CT colonography can be used to also check for other problems like osteoporosis or hardening of the arteries.

Researchers noted that their simulation is in line with previous results, but that as a simulation it can’t prove a direct cause-and-effect link between the screening methods and reduced rates of colon cancer.

More information

The American Cancer Society has more on colon cancer screening.

SOURCES: Radiological Society of North America, news release, June 10, 2025; Radiology, June 2025