TEC Assessment Index

Special Report: Critical Appraisal of CT Colonography Cost-Effectiveness Analyses

Executive Summary

Background

Computed tomographic (CT) colonography, also known as "virtual colonoscopy," is an imaging technique of the colon involving helical computed tomography and computer software to generate high-resolution 2-dimensional and 3-dimensional images of the inner surface of the colon. These images are then interpreted by a radiologist to determine the presence of several types of abnormalities of the colon. CT colonography has been investigated as a technique for colon cancer screening. Concerns about its effectiveness and costs have been raised. This Special Report is a companion piece to the latest clinical TEC Assessment on CT colonography.

Objective

To review and critically appraise cost-effectiveness analyses of CT colonography, specifically to compare CT colonography and colonoscopy.

Search Strategy

Studies that examine cost-effectiveness of CT colonography with adequate methodology and with a comparison with colonoscopy. Studies needed to reveal sufficient data on assumptions, calculate overall life-expectancy or life-year benefits of different strategies, and allow a calculation of an incremental cost-effectiveness ratio.

Main Results

Seven published studies were selected. Two studies completely simulate assumptions that are consistent with current diagnostic capability of CT colonography and recommended practice guidelines. CT colonography was a dominant or cost-effective option only in the one study that added CT colonography's benefit of detection of aortic aneurysm and extracolonic cancers. Without this set of study results, in general, colonoscopy was generally the more effective screening test, and its incremental cost-effectiveness ratio was consistent with a reasonable value for its benefits. The quantity of health benefit afforded by either test is fairly similar.

Authors' Comments and Conclusions

Due to differing assumptions, current cost-effectiveness studies vary in their evaluation of the comparative costs and effects of CT colonography and colonoscopy with currently available data and practice guidelines. Overall benefit without consideration of costs appears to be similar between the two tests regarding colon cancer prevention. Most studies did not consider the potential benefits of aortic aneurysm detection and extracolonic cancer detection, CT colonography was generally more expensive and in many studies less effective as a screening strategy than colonoscopy, and in other studies only slightly more effective. Thus it generally was either dominated by colonoscopy or had a very unfavorable incremental cost-effectiveness ratio.

Depending on the study, at a cost of CT colonography relative to that for colonoscopy within the range of 0.22 to 0.52, CT colonography had reasonable incremental cost-effectiveness ratio compared to colonoscopy. The relative costs of CT colonography and colonoscopy are extremely critical parameters for this analysis. None of the aforementioned studies included the costs of anesthesia; costs for colonoscopy may be particularly high when anesthesiologists provide pain control. More solid information is needed on the relative costs of the two procedures.

Only one study incorporated health benefits of aortic aneurysm detection, extracolonic cancer detection, and long-term radiation effects. This benefit was calculated to account for up to 20% of the total health benefit achieved. Most of the benefit was estimated to be from early detection of aortic aneurysms. Screening for aneurysm using ultrasound has been demonstrated to be effective in older (i.e., age 65 or older) men and has been recommended for older male smokers. Screening for the other cancers assumed to be detected has not been shown to be effective. Further research is needed to bolster the data supporting considerable benefit of CT colonography regarding aortic aneurysm, especially in older individuals, and extracolonic cancer detection, as well as the costs and potential health risks of false-positive findings.

TEC Assessment Index

2D; 3D; ACRIN; adenomas; bowel preparation; colon cancer; computed tomography; credentialing; extracolonic; flat; high-grade dysplasia; interobserver agreement; invasive carcinoma; lesions; multidetector row; neoplasia; oncology; optical colonoscopy; polyps; prevalence; radiologist; reference standard; screening; sensitivity; specificity; stool tagging; stool tagging; tomographic; training; ultrafast; villous features; cost effectiveness; comparative; ICER; incremental; cost effectiveness ratio; modeling; modeling; assumptions; aortic aneurysm; AAA; dominated; nonpolypoid; economic evaluation; CTC;