The cost-effectiveness of screening for colorectal cancer

Abstract

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 cost-effective 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.

Figure 1

Markov states for the natural history of colorectal cancer. Individuals transitioned to different Markov health states (straight arrows) or remained in their current health state (curved arrows). Transitions occurred yearly from age 50 years to death. The Markov model contained three precancer states, three preclinical (undiagnosed) cancer states, three diagnosed cancer states and the absorbing health state of death. After treatment of colorectal cancer, individuals entered a surveillance health state with the opportunity for development of further adenomas and cancer. The 10 screening strategies were superimposed on the natural history model.

Figure 2

Cost-effectiveness plane for not screening and for three strategies for colorectal cancer screening. The graph plots the cost of the various strategies against average discounted quality-adjusted life expectancy.

Figure 3

Cost-effectiveness acceptability curve. The gain in quality-adjusted life years estimated with each strategy was adjusted for the cost and a hypothetical payer’s willingness to pay. The probability that a strategy is cost-effective (y axis) relative to alternative strategies is shown for a range of willingness to pay, up to $100 000 per quality-adjusted life-year gained (x axis).