Colorectal Cancer: Cost-effectiveness of Colonoscopy versus CT Colonography Screening with Participation Rates and Costs

Abstract

Purpose To compare the cost-effectiveness of computed tomographic (CT) colonography and colonoscopy screening by using data on unit costs and participation rates from a randomized controlled screening trial in a dedicated screening setting. Materials and Methods Observed participation rates and screening costs from the Colonoscopy or Colonography for Screening, or COCOS, trial were used in a microsimulation model to estimate costs and quality-adjusted life-years (QALYs) gained with colonoscopy and CT colonography screening. For both tests, the authors determined optimal age range and screening interval combinations assuming a 100% participation rate. Assuming observed participation for these combinations, the cost-effectiveness of both tests was compared. Extracolonic findings were not included because long-term follow-up data are lacking. Results The participation rates for colonoscopy and CT colonography were 21.5% (1276 of 5924 invitees) and 33.6% (982 of 2920 invitees), respectively. Colonoscopy was more cost-effective in the screening strategies with one or two lifetime screenings, whereas CT colonography was more cost-effective in strategies with more lifetime screenings. CT colonography was the preferred test for willingness-to-pay-thresholds of €3200 per QALY gained and higher, which is lower than the Dutch willingness-to-pay threshold of €20 000. With equal participation, colonoscopy was the preferred test independent of willingness-to-pay thresholds. The findings were robust for most of the sensitivity analyses, except with regard to relative screening costs and subsequent participation. Conclusion Because of the higher participation rates, CT colonography screening for colorectal cancer is more cost-effective than colonoscopy screening. The implementation of CT colonography screening requires previous satisfactory resolution to the question as to how best to deal with extracolonic findings. ^© RSNA, 2018 Online supplemental material is available for this article.

Model Appendix Figure 1.

An Overview of the Natural History Module of the microsimulation model.

Model Appendix Figure 2.

Adenomas Prevalence Simulated by the microsimulation model Versus Observed in Selected Autopsy Studies and corrected for differences in CRC incidence with the Netherlands.*

Model Appendix Figure 3.

CRC Incidence Observed Bef ore the Introduction of Screening Versus Simulated by the microsimulation model; cases per 100,000 person years)

Model Appendix Figure 4.

Distal CRC Incidence Observed in the Intervention Group of the UK Flexible Sigmoidoscopy Trial Versus Simulated by the microsimulation model (per year of follow-up (A), cumulative (B); cases per 100,000 person years).

Model Appendix Figure 5.

Integrating Modules: Two example Patients.

Model Appendix Figure 5.

Integrating Modules: Two example Patients.

Appendix Figure 6a:

Sensitivity analysis of all 480 screening strategies with observed participation

Appendix Figure 6b:

Sensitivity analysis including available data on extracolonic findings Scenario A*

Appendix Figure 6c

QALY’s and costs of efficient strategies in all other sensitivity analyses

Figure 1:. The four different simulated follow-up strategies for CTC screening which differ when 6–9 mm adenomas were found.

In all four strategies, individuals with lesions of ≥10mm at CTC were immediately referred for diagnostic colonoscopy, and individuals without lesions or with lesions 1–5mm at CTC returned to the screening program. The follow-up strategies differed in the management of medium sized lesions (6–9mm) seen at CTC. Individuals with medium-sized lesions 1) were directly referred for diagnostic colonoscopy (i.e. using a cut-off of 6mm); 2) returned to the screening program (i.e. corresponding with a 10mm cut-off); 3) and 4) were offered a follow-up CTC after 3 years, as was done in the ___-trial and referred to a diagnostic colonoscopy if they at follow-up CTC had 3) a medium or large lesion, or 4) a large lesion. In the 4^th strategy, persons with medium-sized adenomas continued to receive follow-up CTC, either until a large lesion was detected or until a medium lesion was no longer detected.

Figure 2:. Modeled costs and QALY’s gained per 1000 participants for four CTC screening strategies and colonoscopy screening, with different starting and stopping ages and screening intervals, 3% discounted, from a participant’s perspective.

* Strategies on this frontier are presented in table 3a † CTC strategy number correspond with numbers presented in Figure 1

Figure 3:. Modeled costs and QALY’s gained per 1000 invitees of CTC strategies 6 mm cut-off and colonoscopy with different starting and stopping age and screening interval, 3% discounted, from a population’s perspective.

* CTC strategy 1 in figure 1