Economic Models of Colorectal Cancer Screening in Average-Risk Adults Workshop Summary (2005) / Chapter Skim
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Appendix H Overview of the Vijan Colorectal Cancer Screening Model--Sandeep Vijan, M.D., M.S.
Appendix H Overview of the Vijan Colorectal Cancer Screening Model--Sandeep Vijan, M.D., M.S.
Pages 105-117
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, but since that time we have made improvements which will be described here. I would like to acknowledge Erica Wong, who assisted me on early stages of this project and Rodney Hayward and Tim Hofer, who provided guidance along the way.
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106 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 2 SLIDE 2 NOTES: Our model uses a Markov cohort structure that produces expected endpoints of total lifetime costs, life expectancy, and colorectal cancer incidence and mortality. It is designed to simulate the natural history of colorectal cancer based on the experience of the U.S.
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What happens after detection whether the patient dies from CRC or from some other cause depends on the stage at which the symptoms developed.
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Cancer incidence in this model was based on SEER data from the early 1990s. We chose that period because data from earlier decades might not reflect changes in risk factors and natural history over time.
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APPENDIX H 109 increased by about 2 years in a cohort of 50-year-old individuals. That 2-year difference leads to substantially lower life-expectancies in our model.
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110 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 6 SLIDE 6 NOTES: The chart in this slide compares the model predictions of polyp prevalence with the autopsy data. Although we calibrated our model using visual inspection, the resulting close fit between observed and predicted values suggests a high degree of calibration.
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APPENDIX H 111 SLIDE 7 SLIDE 7 NOTES: This chart compares our model prediction for cumulative CRC risk in the population with the SEER cancer incidence data from age 50 through 100. The close calibration for CRC as a whole is also seen for each stage of CRC (data not shown)
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For example, as shown above, assuming 75% compliance with follow-up among individuals who comply with the screening test reduces the effectiveness of FS and FOBT screening by 81 percent compared with perfect compliance. That is less than the reduction in effectiveness when compliance with follow-up is set at 25%.
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That change has an enormous impact on the cost of this intervention.
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114 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 10 SLIDE 10 NOTES: We used the Medicare reimbursement schedule to estimate test costs. FOBT is not reimbursed as a physician expense, but is paid for as a laboratory test.
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As with all of the models described in the current workshop, we took a third-party payer approach with respect to measuring costs. That means that we did not include the value of lost work time (productivity costs)
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Compared with retrospective cohort studies that examined flexible sigmoidoscopy, we predicted lower mortality on the whole. We are currently examining why our model differed from those studies.
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New York: Oxford University Press. Mandel JS, Bond JH, Church TR, Snover DC, Bradley GM, Schuman LM, Ederer F
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