EVALUATING COLORECTAL CANCER SCREENING OPTIONS FOR CANADA USING ONCOSIM
We set out to predict the effect of different screening tests (fecal occult blood (FOBT), fecal immunochemical test (FIT), flexible sigmoidoscopy and colonoscopy) and schedules on Colorectal Cancer (CRC) outcomes and costs in average and elevated risk subjects in a Canadian context.
We used the OncoSim (formerly called the Cancer Risk Management) microsimulation model developed by the Canadian Partnership Against Cancer to assess the impact of interventions on cancer outcomes and costs in Canada. OncoSim-CRC includes a natural history model where CRC is assumed to develop from adenomas, and is calibrated to Canadian incidence and mortality rates, and costs. OncoSim-CRC is Web based and permits the user to specify parameter values and screening strategies as required. Elevated risk subjects were those with a first-degree family history of CRC and average risk were others.
All screening scenarios considered reduced the incidence and mortality of CRC compared to no screening: predicted CRC cases and deaths prevented ranged from 0.88 to 5.20 and from 0.93 to 2.41 per 100 screened respectively assuming 100% compliance. Net discounted costs were predicted to be less than that for no screening for all strategies considered except those based upon FOBT. Colonoscopy screening, consisting of screens at ages 50, 60 and 70, was predicted to be most effective but required 122.9 colonoscopies per death prevented in average risk: this was more than 3 times the number of follow-up colonoscopies per death prevented for any of the strategies based upon other screening tests. Colonoscopy in high risk subjects had rates of colonoscopy per death prevented comparable to that for other screening tests in average risk subjects. Colonoscopy screening was the most cost-effective strategy in both average and elevated risk subjects. After colonoscopy, strategies based upon FIT testing were predicted to be the most cost-effective. Sensitivity analyses were performed for FOBT and FIT screening strategies. Parameters for high sensitivity FOBT formulations produced a substantial increase in effectiveness and cost-effectiveness of this test.
OncoSim predicted that all considered screening scenarios reduced CRC incidence and mortality at acceptable costs. Sensitivity analysis indicated that some uncertainty existed in the magnitude of the improvements. Where possible local data should be used to reduce uncertainty in parameters and estimate the impact of real world compliance.