CT Colonography Beats Stool DNA Testing for Colon Cancer Screening
Computed tomography (CT) colonography is a more cost-effective and more clinically effective method for colorectal cancer screening than stool DNA testing.
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Computed tomography (CT) colonography is a more cost-effective and more clinically effective method for colorectal cancer screening, compared to stool DNA testing (mt-sDNA), new research published in Radiology suggests.
The study is particularly timely, given the rising incidence of colorectal cancer, especially among younger populations, prompting the U.S. Preventive Services Task Force and several medical societies to recommend initiating screening at age 45.
Current colorectal cancer screening methods
Colorectal cancer, which is the second leading cause of cancer-related deaths worldwide, is primarily screened for using colonoscopy in the United States. Although optical colonoscopy is generally preferred as it also allows for the removal of precancerous polyps during the procedure, it is also the most expensive and invasive option. This has led to increased interest in less invasive and more affordable screening methods, such as stool DNA testing and CT colonography.
CT colonography
CT colonography, also known as virtual colonoscopy, uses a CT scan to create detailed images of the colon and rectum. It is a non-invasive alternative to traditional colonoscopy for detecting colorectal cancer and precancerous polyps.
While stool DNA testing, which detects biomarkers in stool samples, and CT colonography are safer and less invasive than traditional colonoscopy, their effectiveness in detecting and preventing cancer required further evaluation. Researchers conducted a study to assess the relative clinical efficacy and cost-effectiveness of these two approaches.
Study methodology and findings
Using a Markov model, researchers simulated the progression of colorectal disease in a group of 10,000 individuals, all aged 45. The model was constructed using updated natural history evidence for colorectal polyps and assumed perfect adherence to screening, diagnostic follow-ups and recommended care over a simulated period from ages 45 to 75. Consistent with current studies, 7.5% of the study population developed colorectal cancer in the absence of screening.
Markov model
In probability theory, a Markov model is a stochastic model that describes a sequence of possible events where the probability of each event depends only on the state attained in the previous event. Markov models are frequently used in decision analysis and are one of the common types of model used in the economic evaluation of healthcare interventions.
Both CT colonography and stool DNA testing were judged to be clinically effective, with CT colonography showing a higher reduction of colorectal cancer incidence of 70–75%, compared to the 59% reduction achieved by stool DNA testing.
The researchers also conducted an analysis of the cost-effectiveness of each screening method using Quality-Adjusted Life Years (QALYs), a measure that quantifies the value of a medical intervention in terms of quality of life and life expectancy. Although stool DNA testing was deemed cost-effective (at approximately $9,000 per QALY), CT colonography was still found to be cost-saving in comparison to no screening.
Interestingly, the study revealed that a hybrid approach – using CT colonography for three years of surveillance of small polyps followed by colonoscopy for larger polyps – outperformed a strategy of only referring patients with detected polyps greater than 6 mm for colonoscopy. This hybrid approach was more cost-effective, largely due to the lower costs of surveillance and the prevention of unnecessary colonoscopies.
Implications of the study
“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, MD, the John R. Cameron professor of radiology and medical physics at the University of Wisconsin School of Medicine and Public Health in Madison.
“Furthermore, CT colonography can provide for extracolonic screening for things like osteoporosis and cardiovascular disease.”
Overall, this research contributes to the growing body of evidence that supports the use of CT colonography as an important tool for early detection and prevention of colorectal cancer, with the potential to expand access to screening, especially for underserved populations.
Reference: Pickhardt PJ, Correale L, Hassan C. CT colonography versus multitarget stool DNA test for colorectal cancer screening: A cost-effectiveness analysis. Radiology. 2025. doi: 10.1148/radiol.243775
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