CT Colonography Beats Stool DNA Testing for Colon Cancer Screening

By MedImaging International staff writers
Posted on 10 Jun 2025

Image: Images of positive CT colonography screening examination result in an asymptomatic 67-year-old man (Photo courtesy of Radiology)

As colorectal cancer remains the second leading cause of cancer-related deaths worldwide, early detection through screening is vital to reduce advanced-stage treatments and associated costs. In response to a growing incidence in younger populations, the U.S. Preventive Services Task Force has revised the recommended starting age for colorectal screening to 45. While colonoscopy is still the gold standard due to its ability to remove precancerous polyps, expanded Medicare coverage now includes less invasive methods such as multitarget stool DNA (mt-sDNA) testing and CT colonography. Now, a new study has found CT colonography to be both clinically effective and cost-saving when compared to stool DNA testing.

In the study, researchers at the University of Wisconsin School of Medicine and Public Health (Madison, WI, USA) compared mt-sDNA and CT colonography head-to-head. Using a Markov model, they simulated colorectal disease progression in a population of 10,000 individuals starting at age 45 and continuing until age 75, assuming perfect adherence to all screenings and follow-ups. Health states were assigned annually based on lesion presence and size. Without screening, 7.5% of the simulated population developed colorectal cancer.

Published in Radiology, the findings show that both methods were clinically beneficial compared to no screening. However, CT colonography led to a greater reduction in cancer incidence, between 70% to 75%, versus 59% for mt-sDNA. To evaluate cost-effectiveness, the team used Quality-Adjusted Life Years (QALYs), where one QALY equals one year in perfect health. mt-sDNA offered good value at a cost of around USD 9,000 per QALY gained, below the USD 100,000 threshold. In contrast, CT colonography was found to be outright cost-saving compared to no screening.

Because large polyps (≥10 mm) are the key target for prevention, the study also tested a hybrid strategy: 3-year surveillance of small polyps (6–9 mm) using CT colonography, with colonoscopy referrals only for large polyps. When compared to the conventional approach—referring all polyps ≥6 mm for colonoscopy—the hybrid strategy was more cost-effective. The conventional method led to higher colonoscopy-related costs that were not justified by the minimal additional QALYs gained. The findings suggest that a hybrid screening approach combining CT colonography surveillance for small polyps with targeted colonoscopy referrals provides the best balance between cost and clinical benefit.

“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,” said study author Perry J. Pickhardt, M.D. “Furthermore, CT colonography can provide for extracolonic screening for things like osteoporosis and cardiovascular disease.”

Related Links:
UW School of Medicine and Public Health