DRAFT: Not for Citation
Despite recent declines in both incidence and mortality, colorectal cancer (CRC) is the second most common cause of cancer death in the United States. CRC screening has been shown to reduce CRC mortality by 15-33% in randomized controlled trials with Hemoccult II fecal occult blood testing (FOBT). Novel CRC screening technologies, such as computed tomography (CT) colonography have been developed but need to be evaluated in terms of their comparability of performance (sensitivity and specificity) in detecting adenomatous polyps and CRC, acceptability to patients, and test-related complications and costs. Accordingly, we conducted a cost-effectiveness analysis of CT colonography and other currently recommended CRC screening strategies.
We used three microsimulation models from the National Cancer Institute-funded Cancer Intervention and Surveillance Modeling Network (CISNET) consortium to assess the cost-effectiveness of screening for CRC with CT colonography in comparison to the currently-recommended CRC screening strategies. We conducted incremental cost-effectiveness analyses by comparing the incremental costs and benefits with the next best strategy after eliminating dominated strategies (i.e., strategies that are more costly and less effective than another strategy or a combination of other strategies). We conducted a literature review of the evidence for CT colonography to obtain estimates of its sensitivity and specificity for adenomas by size and for CRC. We used previously developed estimates of the direct medical costs of screening, screening-related complications, and treatment, as well as direct beneficiary costs and time costs associated with screening and treatment to be used in analyses from the modified societal perspective. We assumed a per-test cost of $488 for CT colonography (the national average CMS payment for an abdominal CT, a pelvic CT, and image processing) and assumed that the test would be performed every 5 years with individuals with a lesion 6mm or larger referred for colonoscopy. We performed sensitivity and threshold analyses on the cost, screening interval, size of lesion triggering colonoscopy referral, diagnostic performance, and relative adherence of CT colonography.
Assuming equal adherence across all tests, the screening benefit for 5-yeraly CT colonography, measured in terms of discounted life-years gained compared with no screening, was 2-7 life-years lower than colonoscopy screening every 10 years but comparable to that of 5-yearly flexible sigmoidoscopy plus annual FOBT. At a per test cost of $488 the overall costs for the CT colonography strategy were higher than all of the other screening strategies. CT colonography screening could be cost-effective (i.e., be a non-dominated strategy) at per-test cost of $108 to $205 per scan depending on the simulation model used and the test characteristics of CTC. If the cost per scan were $179 to $237, CT colonography screening would have the same cost per life-year gained as colonoscopy. If screening adherence were higher with CT colonography compared with other screening tests, CT colonography screening could be included among the efficient strategies at the base-case cost estimate.
Based on the analyses from three microsimulation models, screening for CRC with CT colonography every 5 years with referral of individuals with a 6 mm or larger lesion to colonoscopy provides a benefit in terms of life-years gained that is comparable to that of five-year flexible sigmoidoscopy with annual FOBT and slightly lower than colonoscopy screening every 10 years. The cost of CT colonography relative to the benefit derived and to the availability and costs of other CRC screening tests, would need to be in the range of $108 to $205 to be a cost-effective alternative to all other available screening modalities, and in the range of $179 to $237 to be cost-effective compared to colonoscopy screening.