CT Colonography a Better Alternative to FIT and Reliable Alternative to Colonoscopy
Recent evidence and expanded coverage strengthen the case for adopting CTC as a high-value option in average-risk CRC screening
Colorectal cancer (CRC) isn’t only one of the most commonly diagnosed cancers, it’s also one of the most lethal. Perhaps even more concerning is that the American Cancer Society recently reported a rapid increase in CRC rates among young adults, with one in five new diagnoses now occurring in people under 55.
With the right lifestyle choices and regular screening, CRC is also highly preventable.
Capable of allowing direct and full inspection of the colon and simultaneous removal of precancerous polyps, colonoscopy remains the gold standard for CRC screening. But it’s also highly invasive, which could be a factor in why many people fail to be properly screened.
According to some estimates, in the United States, 59% of adults aged 45 years or older are up to date with their screening. In the subgroup of adults aged 45-49, the screening rate is only 20%—far short of the 80% national goal.
To help increase screening levels, more physicians are adopting less-invasive screening alternatives like fecal immunochemical test (FIT) and CT colonography (CTC).
Whereas FIT is a quick, noninvasive stool test that can be performed at home without bowel preparation, CTC is a minimally invasive imaging test that requires bowel preparation and must be performed in a clinical setting.
While FIT may be less invasive, how does it perform compared to CTC?
“When weighing the two exams, the evidence is clear that average- or low-risk patients are better served by CTC than FIT for CRC screening,” said Jason A. Pietryga, MD, a senior associate consultant in the Division of Emergency and Hospital Radiology, Department of Radiology at Mayo Clinic in Florida.
Dr. Pietryga co-authored an editorial on the topic with David Kim, MD, a professor of radiology in abdominal imaging and intervention, and vice chair of education for the Department of Radiology at the University of Wisconsin in Madison.
CT Colonography as the Better Alternative
Drs. Pietryga and Kim’s editorial accompanied a recent study published in Radiology in which researchers from Italy compared CTC and FIT and determined that CTC had a higher incidence rate of detection of advanced adenomas (91% vs 79.2%)—a precursor to cancer that allows for greater primary prevention.
In the study, cancers were detected at initial screening (88.9% vs 41.4%) by CTC resulting in earlier diagnosis within the cohort.
By comparison, most cancers detected in the FIT cohort were identified after the initial screening trial, resulting in later diagnosis. This delay helps explain why all stage IV cancers were found in the FIT cohort.
According to Dr. Pietryga, the main disadvantage of CTC was a lower participation in the CTC screening cohort compared to the FIT screening cohort (26.6% vs 64.9%). This difference in participation rates is likely explained by the ease of use and lack of bowel prep with FIT testing.
Drs. Pietryga and Kim argue that CTC should be positioned as a better alternative to FIT screening. “Not only is CTC better at detecting CRC and advanced adenomas, it also has a higher positive predictive value than FIT,” Dr. Pietryga emphasized. “This is important as optical colonoscopy is not without risks, and patients with positive CTC and FIT go on to further evaluation with colonoscopy.”
“When weighing the two exams, the evidence is clear that average- or low-risk patients are better served by CTC than FIT for CRC screening.”
— JASON A. PIETRYGA, MD
CT Colonography as Reliable as Colonoscopy
But how does CTC compare to colonoscopy?
While the Radiology study doesn’t compare the two, Dr. Kim noted that studies show CTC to be just as reliable as the current gold standard.
After a systematic review of the literature, the U.S. Preventive Services Task Force (USPSTF) concluded that CTC performance is equivalent to colonoscopy for polyps 6 mm or greater in size. This means CTC can easily detect clinically relevant precancerous lesions, which are typically 1 cm or larger.
“In addition to detecting cancer, like all screening tests, CTC can prevent cancer while reducing risks of perforation or sedation that are present at colonoscopy,” Dr. Kim said.
He noted that patients with negative CTC screening results do not need to undergo colonoscopy, thereby avoiding those procedure-related risks.
Increasing the Use of CT Colonography Starts with Radiologists
Drs. Kim and Pietryga say CTC should be widely used in average risk screening. So, why isn’t it?
Until recently, one factor was a lack of Medicare approval for reimbursement. That changed when Medicare approval was granted for the procedure in January 2025. “But after so many years of coverage denials, many primary care providers still wrongly believe that CTC is experimental,” Dr. Kim said.
Dr. Kim also highlighted radiologist interest as being a potential barrier to widespread use of CTC because, as he pointed out, the exam carries a learning curve. However, he said that high accuracy is attainable for a radiologist with solid experience in abdomen pelvic CT.
“Hopefully, CTC use will go up with reimbursement and increased radiologist involvement as the exam’s obvious advantages become more evident over time,” Dr. Kim said.
“As CT is ubiquitous in the U.S. health care system, the possibility of increasing CRC screening with CTC has great potential, particularly if we can educate both providers and average risk patients regarding the utility and safety of CTC,” Dr. Pietryga concluded.
For More Information
Access the Radiology study, “Colorectal Cancer and Advanced Adenoma after Single CT Colonography or Biennial FIT Screening in the SAVE Randomized Controlled Trial,” and the related editorial, “CT Colonography Is The More Fit Colorectal Cancer Screening Test.”
Read previous RSNA News stories on abdominal imaging: