New research examining the role of computed tomography colonography (CTC) in colorectal cancer (CRC) screening over the course of 20 years revealed significant correlation to subsequent optical colonoscopy (OC) findings for detection of polyps > 6 mm.
For the retrospective study, recently published in the American Journal of Roentgenology, researchers reviewed data for 15,341 CTC exams performed for 11,830 patients (mean age of 56). The cohort included 9,168 patients who had CTC exams for primary asymptomatic CRC screening, according to the study.
For patients who had primary asymptomatic CRC screening with CTC, the researchers noted a 15.9 percent rate of positive findings for polyps > 6 mm. Overall, out of 1,683 cases involving CTC-detected polyps > 6 mm, the study authors found concordant lesions on OC in 1,541 of these cases for a 91.6 percent positive predictive value (PPV).
The use of CTC also led to detection of advanced adenoma (4 percent), extracolonic malignancy (0.4 percent) and abdominal aortic aneurysm (0.3 percent). The researchers added there were no major complications or colonic perforations with CTC.
“These findings support the use of CTC as a safe non-invasive test for asymptomatic screening, providing CRC prevention and detection along with extracolonic assessment,” wrote lead study author Perry J. Pickhardt, M.D., the chief of gastrointestinal imaging in the Department of Radiology at the University of Wisconsin School of Medicine and Public Health, and colleagues.
With respect to polyp morphology, the study authors noted that CTC had a 94.1 percent PPV for sessile lesions and a 95.7 percent PPV for pedunculated polyps.
Three Key Takeaways
- High predictive accuracy for polyps. CTC showed a 91.6 percent positive predictive value (PPV) for polyps ≥ 6 mm, with particularly strong performance for identifying sessile (94.1 percent PPV) and pedunculated polyps (95.7 percent PPV), affirming its diagnostic accuracy compared to optical colonoscopy (OC).
- Non-invasive and low-risk screening option. CTC proved to be a safe, non-invasive screening method with no major complications or colonic perforations reported. It also allowed detection of clinically relevant extracolonic findings, such as advanced adenomas (4 percent), extracolonic malignancies (0.4 percent), and abdominal aortic aneurysms (0.3 percent).
- Viable CRC screening alternative despite declining use. Although CTC utilization for primary CRC screening declined sharply (from 1,589 exams in 2005 to 72 in 2023) at the study facility, the study supports its continued role as a viable CRC screening alternative, especially with recent Medicare coverage determinations for CTC.
While the researchers noted a precipitous decline in CTC utilization from 2005 to 2023 for primary asymptomatic screening (1,589 CTC exams in 2005 vs. 72 CTC exams in 2023), they maintained that the study findings and the recent national coverage determination for CTC screening of Medicare beneficiaries make CTC a viable alternative for CRC screening.
“Through proper technique, CTC screening can provide noninvasive CRC prevention that is lacking with stool-based tests, avoid the complications associated with primary OC screening, and provide the unique additional benefit of extracolonic evaluation,” emphasized Pickhardt and colleagues.
(Editor’s note: For related content, see “Study: CT Colonography Screening Offers Up to 16 Percent Higher Reduction of Colorectal Cancer Incidence than Cologuard,” “Incorporating CT Colonography into Radiology Practice” and “Survey Results Reveal Doubling of CT Colonography Use During COVID-19 Pandemic.”)
Beyond the inherent limitations of a single-center retrospective study, the authors conceded a lack of systematic documentation for colorectal lesions missed by CTC and no assessment of outcomes with respect to variances among individual radiologists.
