Economic Models of Colorectal Cancer Screening in Average-Risk Adults Workshop Summary (2005) / Chapter Skim
Currently Skimming:
Appendix G The Vanderbilt Colorectal Cancer Model--R.M. Ness, R.W. Klein, R.S. Dittus
Appendix G The Vanderbilt Colorectal Cancer Model--R.M. Ness, R.W. Klein, R.S. Dittus
Pages 84-104
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 84... ...
Dittus SLIDE 1 SLIDE 1 NOTES: The materials presented in this workshop are based on our current working version of the model. It was adapted from a paper published in 2000 (Ness et al., 2000)
|
From page 85... ...
A discrete-event structure gives the modeler the ability to assign specific attributes to each simulated patient (e.g. the underlying risk of adenoma incidence)
|
From page 86... ...
. The major steps in neoplasm development include normal tissue, adenoma, asymptomatic CRC and symptomatic CRC.
|
From page 87... ...
Anything that alters clinical knowledge such as diagnostic tests or surgical interventions can lead to transitions between the adenoma and CRC states.
|
From page 88... ...
The fit resulted in a mean progression time for fastprogressing adenomas of 26 years; and for slow-progressing adenomas of 75 years. The rate of progression from asymptomatic to symptomatic CRC is based on a previous mathematical analysis using the prevalence of malignant polyps to predict the mean latency period before CRC becomes symptomatic (4.8 years)
|
From page 89... ...
. SLIDE 6 SLIDE 6 NOTES: The National Polyp Study followed a cohort of 1400 people with identified adenomas on screening for 6 years following polypectomy.
|
From page 90... ...
. This graph plots prevalence in terms of persons with adenomas/100 people against patient age.
|
From page 91... ...
But, if such lesions are discovered on sigmoidoscopy or radiology, they might generate a full optical colonoscopy. That followup procedure could well find an adenoma by random happenstance.
|
From page 92... ...
In determining who is referred to followup for a positive test, and what happens to them on the followup examination, we interpret test specificity as reported in the literature to imply specificity for all polyps (adenomatous and non-adenomatous) in the case of endoscopic or radiologic screening modalities, but not in the case of FOBT tests (Allison et al., 1996; Allison et al., 1990)
|
From page 93... ...
This maximum testing frequency was programmed as a patient-specific characteristic. In practice, this created rates of effective adherence that varied between testing modalities and screening strategies (e.g.
|
From page 94... ...
. Simulated patients assigned to limited adherence with screening were more likely to be modeled as non-compliant with surveillance.
|
From page 95... ...
. Those costs are reported by in three phases initial care, continuing care, and terminal care.
|
From page 96... ...
One could examine, for example, the overall cost-effectiveness of decrease cancer risk at the same time as screening individuals for cancer. We can also model the prognostic capabilities of diagnostic testing modalities.
|
From page 97... ...
We noticed that, when all parameters were standardized to values provided by the organizers of the pre-workshop exercise (Run #6-see Pignone presentation) , the Vanderbilt model's lifetime costs appear to be much higher than the lifetime costs reported by all other models.
|
From page 98... ...
98 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 15 SLIDE 15 NOTES: In the "new" runs, we assumed that all polyps are adenomas and that their prevalence and incidence are given by the autopsy studies. Thus, we eliminated nonadenomatous polyps from the model.
|
From page 99... ...
When we removed the non-adenomatous polyps from the model, the costs generated by the Vanderbilt model, especially for the strategies involving sigmoidoscopy were more in line with the costs recognized for the rest of the group.
|
From page 100... ...
100 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 17 (BLANK) SLIDE 17 is blank.
|
From page 101... ...
On the other hand, there would be a small increase in effectiveness because of a decrease in mortality from complications of followup colonoscopy. The attached charts show that there is, on balance, decreased effectiveness associated with the strategies that involve sigmoidoscopy when non-adenomatous polyps are excluded from the model.
|
From page 102... ...
Still, the FOBT and colonoscopy tests were affected somewhat by removal of the non-adenomatous polyps from the model. That is because any positive FOBT would lead to a followup colonoscopy, where non-adenomatous lesions would be discovered serendipitously and removed.
|
From page 103... ...
APPENDIX G 103 SLIDE 20 SLIDE 21 NOTES: The present slide shows that the incremental cost-effectiveness ratios changed, but the undominated strategies stayed the same when the non-adenomatous polyps were removed.
|
From page 104... ...
39: 22582264. Behavioral risk factor surveillance system online prevalence data, 1995-2001.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.