Economic Models of Colorectal Cancer Screening in Average-Risk Adults Workshop Summary (2005) / Chapter Skim
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Appendix D Overview of Harvard Model--Karen M. Kuntz, ScD.
Appendix D Overview of Harvard Model--Karen M. Kuntz, ScD.
Pages 45-60
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The original PowerPoint presentations are available on the Institute of Medicine website at http://www.iom.edu/crcworkshop.
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. That model was used to produce the results of the Pre-workshop Exercise described elsewhere in the workshop summary.
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(For the pre-workshop exercise, individuals were followed through age 85.) Sixty states of health track different underlying disease states, such as whether a person has a lowrisk or high-risk polyp, and the location of that polyp, whether there is an undiagnosed or diagnosed cancer, and the stage of that diagnosis.
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The probability of such detection varies with the stage of the patient. The progression described above is tracked separately for the distal and proximal colon.
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We varied the estimates of cancer progression and symptom detection across clinically plausible ranges so that the stage distribution and cancer incidence was similar to those reported by the National Cancer Institute's SEER system.
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APPENDIX D 51 SLIDE 5 SLIDE 5 NOTES: This chart shows the fitted regression line for women. The model transition probabilities were constructed so that, for example, in the cohort of women who had survived to 60 years of age, roughly 27 or 28 percent would have at least one polyp.
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We used DevCan data from the late 1970's to predict cancer rates for a population that would not routinely receive screening. (Probabilities for recent years have most likely been affected by the rapid increase in the utilization of colorectal screening tests)
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We used data from the few studies that followed the progression of polyps not removed on first detection, estimates of the dwelling time of cancer by stage, estimates of symptom detection rates, to guide our initial model assumptions, and we ultimately adjusted those assumptions to reach reasonable agreement with the SEER data.
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54 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 8 SLIDE 8 NOTES: This chart summarizes the sources of data used to predict the natural history of colorectal cancer in the absence of screening.
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We also assume that the compliance rate might differ for each screening technology and for follow-up colonoscopies. For example, the compliance rate could be 60 percent for FOBT, but 80 percent for colonoscopy scheduled following a positive screen.
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. That study reported on the net costs of the initial treatment for CRC, a monthly cost of continuing care, and a final cost associated with the last year in which the patient lives.
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We assumed that recurrence rates of low-risk polyps after polypectomy were higher for individuals with a history of a high-risk polyp diagnosis compared with a prior diagnosis of low-risk polyp and that the risk was higher in the first year following polyp removal compared with subsequent years.
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We ran our model for 15 years, the duration of the Minnesota trial. The screened individuals in the trial showed a 33 percent reduction in cancer mortality and an 11 percent reduction in cancer incidence.
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Finally, we are taking a more formal approach to calibrating our model assumptions. We are using statistical maximum likelihood methods to optimize our natural history assumptions.
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: 19541961. Mandel JS, Church TR, Bond JH, Ederer F, Geisser MS, Mongin SJ, Snover DC, Schuman LM.
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