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Cancer Intervention and Surveillance Modeling Network

Modeling to guide public health research and priorities

Comparative Analyses

Comparative Approaches of Colorectal Cancer Simulation Models to Help Inform Health Decision Makers

Our colorectal cancer microsimulation modeling group published two papers in a special issue of Medical Decision Making (July/August 2011) on the benefits of comparative modeling and methods to increase transparency of disease simulation models.  The first paper concentrates on elucidating how different modeling assumptions of the natural history of the adenoma carcinoma sequence may influence the projected outcomes from different interventions (Kuntz 2011). Meanwhile, the second paper proposes an innovative approach for reporting the national history component of models that can easily be compared with other models and is more appealing to a clinical audience.  (van Ballegooijen 2011).

Cost Effectiveness of Stool DNA Screening for Colorectal Cancer

Stool DNA testing for the screening of colorectal cancer represents one of the new screening approaches which has been considered by the Centers for Medicare & Medicaid Services, often the first adopter of innovative screening tests.  CISNET modelers utilizing two different models analyzed the current conditions for which stool DNA could be cost-effective compared to current, reimbursable screening tests.  At the current estimated cost and a screening interval of every 3 – 5 years, modelers found stool DNA tests yielded fewer life-years and higher costs than established, recommended screening methods in both a cohort of CMS persons as well as those of average screening age, 50 years and older.  (Lansdorp-Vogelaar 2010).  Until overall cost of stool DNA screening decreases, this screening strategy does not represent a cost-effective alternative to the majority of currently reimbursable screening tests.

Cost-effectiveness of CT colonography in the Medicare Population

Computed tomographic colonography (CTC) is currently not among the colorectal cancer screening modalities reimbursable by the Centers for Medicare and Medicaid Services (CMS.)  The three CRC CISNET microsimulation models evaluated the reimbursement rate at which CTC screening could be cost-effective compared with the colorectal tests that are reimbursed by CMS (yearly fecal occult blood test (FOBT), flexible sigmoidoscopy every five years, flexible sigmoidoscopy at five years in conjunction with annual FOBT and colonoscopy every ten years.) (Knudsen 2010).  Key assumptions were that CTC was performed every five years and individuals with findings of 6 mm or larger were referred to colonoscopy.  Simulation findings showed that if CTC screening was reimbursed at $448 per scan (slightly less than the reimbursement for a colonoscopy without polypectomy), it would be the most costly strategy.  Furthermore, sensitivity analyses showed that if relative adherence to CTC screening was 25% higher than adherence to other tests, it could be cost-effective if reimbursed at $448 per scan.  Overall CTC could be a cost-effective option for colorectal cancer screening among Medicare enrollees if the reimbursement rate per scan is substantially less than that for colonoscopy or if a large proportion of otherwise unscreened persons were to undergo screening by CTC. 

Rising Chemotherapy Costs and the Impact on Colorectal Cancer Screening Cost Savings

The MISCAN-Colon examined whether colorectal cancer screening would become cost saving with the widespread use of the newer, more expensive chemotherapies (Lansdorp-Vogelaar 2009).  Using general population data, the new chemotherapies were compared to colorectal cancer screening strategies to determine if the new chemotherapies would affect the treatment savings from these tests.  The tests under consideration were annual guaiac fecal occult blood testing (FOBT), annual immunochemical FOBT, sigmoidoscopy every five years, colonoscopy every 10 years, and the combination of sigmoidoscopy every fiver years and annual guaiac FOBT. Treatment savings from preventing advanced colorectal cancer and colorectal cancer deaths by screening more than doubled with the widespread use of new chemotherapies, compared with no screening.  For all screening modalities, except colonoscopy, the lifetime average treatment savings were larger than the lifetime average screening costs.  Colonoscopy net costs did decrease substantially however.  Modeling results showed screening is a desirable approach to control the costs of colorectal cancer treatment. 

Evaluating test strategies for colorectal cancer screening: A decision analysis for the U.S. Preventive Services Task Force

The U.S. Preventive Services Task Force (USPSTF) requested a decision analysis for colorectal cancer to assist the task force in determining the age to begin screening, age to end screening, and intervals of screening for multiple screening tests. This was the first time that the Task Force had used a decision analysis in combination with a systematic evidence review to inform their decisions. CISNET models provided standardized comparisons of 145 screening strategies using the best available evidence for consideration by the USPSTF. Several of these screening strategies gave similar gains in life-years—provided that there is equally high adherence for all aspects of the screening process. Under these conditions, the best screening strategies were high-sensitivity FOBT (Hemoccult SENSA or fecal immunochemical test) performed annually, flexible sigmoidoscopy performed every 5 years with Hemoccult SENSA performed every 2 to 3 years, or colonoscopy performed every 10 years. Annual FOBT with a lower-sensitivity test (Hemoccult II) and flexible sigmoidoscopy alone resulted in fewer life-years gained relative to other strategies. These analyses confirmed the current recommendation to begin screening at age 50 in the asymptomatic general population and showed that stopping screening at age 75 after consecutive negative screenings since age 50 provides almost the same benefit as stopping at age 85 but with substantially fewer colonoscopy resources and risk of complications (Zauber 2008).

Colorectal cancer mortality projections Web site

The Colorectal cancer mortality projections Web site provides a modeling tool that projects future trends in colorectal cancer mortality and evaluates how potential increases in prevention, screening, and access to state-of-the-science cancer treatment may affect future mortality trends. It is intended for policy, legislative, and cancer control planning staff at the federal, state, and local levels, as well as advocacy and professional groups. It also features descriptions of and links to the Healthy People 2010 objectives relevant to colorectal cancer. The Web site has comparative analyses across two groups: MISCAN and the University of Minnesota group (SimCRC). Users may select to compare intervention scenarios, results across race and gender groups, or results across the two models.

Results show that almost half of all colorectal cancer mortality can be eliminated by 2020 by more fully utilizing cancer control opportunities that we already know are effective. Lower levels of utilization will substantially reduce those gains. While increased usage of state-of-the-art treatment has the most immediate impact on mortality, screening over the longer term has the largest impact. Changing the risk factor profile of the U.S. population to optimistic but still realistic levels will take many years to influence colorectal cancer mortality trends, but the benefits extend well beyond colorectal cancer.