CT Colonography Gains Ground in Colorectal Cancer Screening
Medicare coverage and USPSTF support may expand use of a proven screening tool
In concert with the RadioGraphics monograph, RSNA News shares the latest on the role of medical imaging in disease screening.
After generating significant interest in the early 2000s, screening CT colonography (CTC) has remained underutilized, largely due to a 2009 non-coverage decision by the Centers for Medicare & Medicaid Services (CMS) and an initial lack of “A grade” recommendation from the U.S. Preventive Services Task Force (USPSTF).
That changed in January 2025 when Medicare began covering screening CTC. The USPSTF has included the exam for average-risk adults age 50-75 since 2016 with a more recent change to decrease the start of screening at age 45 from 50.
“The 2009 CMS decision has been both a material and a symbolic barrier to the adoption of CTC,” said Michio Taya, MD, assistant professor of radiology in the abdominal imaging and intervention section at the University of Wisconsin School of Medicine and Public Health in Madison. “However, two decades of science have affirmed that CTC is essentially equivalent to traditional colonoscopy in terms of sensitivity and safety.”
Expanded insurance coverage for screening CTC comes as colorectal cancer has become the leading cause of cancer deaths for adults younger than 50. Despite this statistic, the prevalence of screening among adults 45 and older is only 59%. CTC remains particularly underused: its utilization rate among adults ages 50 to 75 has ranged between 1.3% and 2.1% since 2010.
“CTC is well-suited to address this population health need,” Dr. Taya said. “However, many primary care physicians still hold the belief that CTC is investigational and not fully validated.”
The Benefits of Selective Polypectomy and Surveillance
CTC’s selective polypectomy and surveillance strategy is grounded in long-term data demonstrating that most diminutive polyps remain stable or regress, with an extremely low risk of cancer.
Lesion size and number are used to stratify risk and guide management decisions. Larger polyps are more likely to harbor advanced pathology and are generally referred for immediate removal, while smaller polyps can often be safely monitored. “Some small polyps remain stable for years or even regress,” Dr. Taya said. “Surveillance allows us to identify the lesions that demonstrate growth and are more likely to benefit from intervention.”
In a 2007 New England Journal of Medicine study by Kim et al., CTC’s selective polypectomy strategy and colonoscopy achieved a similar yield of advanced neoplasia. The number of polyps removed during colonoscopies was four-fold higher than with CTC and resulted in seven perforations, compared to none with CTC.
Patients receiving colonoscopy underwent 2,434 polypectomies, while only 7.9% of patients receiving CTC were referred to colonoscopy for 561 polypectomies.
“Colonoscopy often removes pseudo-disease, which incurs excess risk of colonic perforation without benefit,” Dr. Taya said. “Ideally, we want to catch all pre-cancer efficiently and accurately, while minimizing complications. That’s the advantage of CTC: it's safer than optical colonoscopy, but equally efficacious.”
“Ideally, we want to catch all pre-cancer efficiently and accurately, while minimizing complications. That’s the advantage of CTC: it's safer than optical colonoscopy, but equally efficacious.”
— MICHIO TAYA, MD
Dr. Taya emphasized that the benefit is not simply earlier cancer detection. “The goal is to identify precancerous lesions before cancer develops,” he said. “When those lesions are removed, the cancer pathway is interrupted, and the cancer never occurs.”
CTC may also offer an advantage over stool-based DNA tests in detecting precancerous lesions. Although stool-based DNA tests can detect early cancers with reasonable sensitivity, he said they cannot detect precursor lesions to prevent cancer. “That is the main failing of these tests and lost opportunity to make a difference in a person’s life,” Dr. Taya said.
Individuals compliant with stool-based testing could have years of negative exams before conversion to a positive exam when they have cancer. “In such cases, the stool-based screening ‘worked’ and caught an early cancer, but in reality, missed the opportunity to detect the lesion that was present in their colon for several years before transforming into cancer,” Dr. Taya said.
Large 25-mm tubulovillous adenoma in the cecum in a 71-year-old woman. (A, B) Two-dimensional supine CTC image (A) shows an apparent large lesion (arrow in A) on the anterior wall, whereas the two-dimensional prone CTC image (B) shows the possible polyp (arrow in B) on the lateral wall, suggesting movement and thus stool. Part of the learning curve for CTC is the ability to determine if the underlying colon is moving, as often the colon is on a mesentery. In addition, there are characteristic movements such as cecal rotation of 90–180 degrees between supine and prone positioning. Using distance from internal landmarks, such as the ileocecal valve, can be helpful. In this case, the polyp is fixed in position and real with the underlying cecum rotating. (C, D) Three-dimensional CTC (C) and colonoscopic (D) images shows the lobulated morphology of the polyp, which was diagnosed as a tubulovillous adenoma at histologic examination.
https://doi.org/10.1148/rg.260016 ©RSNA 2026
Removing Barriers to Screening CTC
With Medicare coverage now in place, other historic barriers to the screening option are also crumbling. Although reimbursement still varies by payer and region, CTC remains a less expensive, yet equally effective screening test compared to colonoscopy.
National and society-based training programs have also made CTC interpretation more accessible, with radiologists achieving competence after interpreting an average of 164 exams.
“Colonoscopy requires IV access, sedation, recovery time and someone to drive the patient home afterward,” Dr. Taya said. “It’s effectively a full-day commitment with non-trivial procedural and anesthesia risk.”
By comparison, CTC also requires preparation and IV access but does not require sedation or pain medication. This allows patients to return to normal activities immediately after the exam while carrying a much lower risk for colonic perforation.
Increasing CTC use will require outreach to primary care physicians (PCPs), who often guide patients’ screening decisions. Under pressure to raise colorectal cancer screening rates, PCPs often default to stool tests because they are perceived to be the easiest.
“Patients who decide to do stool-based tests have to be willing to potentially undergo a colonoscopy if their test result is positive,” Dr. Taya said. “If a patient is reluctant to undergo colonoscopy because of the time commitment, sedation or invasiveness, that should be part of the screening discussion when considering different test options."
Dr. Taya noted that studies establishing CTC’s effectiveness evaluated it as a first-line screening option rather than a follow-up examination after a positive stool-based test. He added that although researchers have explored that potential use, more research is needed to determine CTC’s role after positive stool DNA tests, including whether negative CTC findings would sufficiently reassure patients and referring physicians.
CTC Safety and Performance
To increase CTC referrals, Dr. Taya emphasized that outreach to PCPs should focus on CTC’s high performance, comparative advantages and safety profile. In a USPSTF systematic review, no significant complications were reported among 17 studies of screening CTC totaling 89,073 patients. Screening colonoscopy had a relatively greater risk of adverse events with 14.6 serious bleeds and 3.1 perforations per 10,000 procedures.
“Many PCPs still believe CTC is investigational,” Dr. Taya said. “Radiologists need to actively correct this outdated perception and help create excitement around this validated, safe and proven test that can help meet a very important and pressing public health need.”
“We have a great opportunity as radiologists to be able to help patients and make a difference in patient lives,” he added. “I think it's very fulfilling and meaningful to be involved with a test that prevents cancer."
For More Information
Access the RadioGraphics article, “CT Colonography: Where Are We with Colorectal Cancer Screening?” and the invited commentary, “Advancing Screening CT Colonography: Timely Update and Call to Action.”
Read previous RSNA News stories on colorectal cancer screening: