Background: Published decision analyses show that screening for colorectal cancer is cost-effective. However, because of the number of tests available, the optimal screening strategy in Canada is unknown. We estimated the incremental cost-effectiveness of 10 strategies for colorectal cancer screening, as well as no screening, incorporating quality of life, noncompliance and data on the costs and benefits of chemotherapy.
Methods:We used a probabilistic Markov model to estimate the costs and quality-adjusted life expectancy of 50-year-old average-risk Canadians without screening and with screening by each test. We populated the model with data from the published literature. We calculated costs from the perspective of a third-party payer, with inflation to 2007 Canadian dollars.
Results:Of the 10 strategies considered, we focused on three tests currently being used for population screening in some Canadian provinces: low-sensitivity guaiac fecal occult blood test, performed annually; fecal immunochemical test, performed annually; and colonoscopy, performed every 10 years. These strategies reduced the incidence of colorectal cancer by 44%, 65% and 81%, and mortality by 55%, 74% and 83%, respectively, compared with no screening. These strategies generated incremental cost-effectiveness ratios of $9159, $611 and $6133 per quality-adjusted life year, respectively. The findings were robust to probabilistic sensitivity analysis. Colonoscopy every 10 years yielded the greatest net health benefit.Interpretation: Screening for colorectal cancer is costeffective over conventional levels of willingness to pay. Annual high-sensitivity fecal occult blood testing, such as a fecal immunochemical test, or colonoscopy every 10 years offer the best value for the money in Canada.
AbstractPreviously published at www.cmaj.ca
Research
Methods
Model designWe developed a Markov model using TreeAge DATA Pro (TreeAge Software Inc., Williamstown, Mass.) to estimate the cost-effectiveness of 10 strategies for screening, as well as no screening, in 50-year-old individuals at average risk for colorectal cancer (Table 1). Screening and surveillance continued until 75 years of age, and the analysis continued through the lifetime of the cohort. The length of the model cycle (or, equivalently, the duration over which an individual remained in the same health state before having the oppor tunity to transition to another health state) was one year. We calculated costs from the perspective of a thirdparty payer such as a provincial ministry of health and inflated these costs to 2007 Canadian dollars. The model output was quality-adjusted life-years. We discounted costs and effects at 5% annually and used a half-cycle correction to account for these discounts.We simulated the natural history of colo rectal cancer (Figure 1). We calibrated the input parameters of incidence and progression of adenoma to colorectal cancer to generate the known age-specific prevalence of adenomas and colorectal cancer (Appendix 2, available at www.cmaj.ca /cgi /content/fu...
