Economic Models of Colorectal Cancer Screening in Average-Risk Adults Workshop Summary (2005) / Chapter Skim
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Appendix F MISCAN-colon: An Overview--Marjolein van Ballegooijen, Iris Vogelaar, Rob Boer, Franka Loeve, Ann Zauber, Gerrit van Oortmar, and Dik Habbema
Appendix F MISCAN-colon: An Overview--Marjolein van Ballegooijen, Iris Vogelaar, Rob Boer, Franka Loeve, Ann Zauber, Gerrit van Oortmar, and Dik Habbema
Pages 73-83
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Appendix F MISCAN-colon: An Overview Marjolein van Ballegooijen, Iris Vogelaar, Rob Boer, Franka Loeve, Ann Zauber, Gerrit van Oortmarssen, and Dik Habbema SLIDE 1 SLIDE 1 NOTES: No notes.
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The net effect of the screening strategy is determined per life history by the changes that occur compared with the baseline. The model provides outputs on a real population in any specific calendar year.
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For example, a person's simulated natural history might be programmed to develop a non-progressive adenoma in the rectum at one time, and another progressive adenoma in the transverse colon at another time. Each of these events will have their own independent history until a first cancer is detected in that simulated individual.
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The length of time required for each person to travel through each phase in the adenoma/carcinoma sequence is determined by the parameters of a probability distribution for each disease stage and for each transition that is specified as part of the model. The model as currently quantified does not permit a cancer to derive directly from a small adenoma.
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We also used SEER CRC incidence data from the late 1970's before screening was prevalent in the USA. We also used the extant autopsy studies to estimate adenoma prevalence, including the prevalence of multiple adenomas in the same individual.
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For now, we assume that if an individual progresses rapidly through the small adenoma state, he or she has a high probability of progressing rapidly through later states. We also assume a positive correlation among the durations of preclinical cancerous states.
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Our model assumes that the probability of compliance with the screening strategy at any screening round depends on the person's compliance history in the previous screening round. Compliance in one round implies, in the model, a higher probability of compliance in the successive round.
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Initial treatment costs cover the first six months; after that, continued CRC-related costs are charged over the remainder of the life, until the last six months, when costs of terminal care are included. However, for the pre-workshop exercise, because individuals would be followed only until age 85, we did not include terminal care costs, even when a simulated person died before the age of 85.
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We have been able to reproduce the results of the Minnesota trial. Our model predicted a 34.6 percent reduction in morality from annual screening and a 20 percent reduction from biennial screening.
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That failure may suggest problems if we are to use the model for improved tests or other strategies. We are therefore currently attempting to validate the model against the three big FOBT trials together, combining the data that are available from each one.
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: 2340. Loeve F, Boer R, Zauber AG, Van Ballegooijen M, Van Oortmarssen GJ, Winawer SJ, Habbema JDF.
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