AVERAGE RISK COLORECTAL CANCER SCREENING: UNDERSTANDING THE CONSEQUENCES OF INTRODUCING COMPETING DEMANDS FOR LIMITED COLONOSCOPY RESOURCES
Campbell, Leslie Anne
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Population-level average risk screening is becoming an important strategy for the control of colorectal cancer. When implementing a population-level colorectal cancer screening program, it is essential to consider how to manage both the short- and long-term consequences of the screening yield and the shifting effects of disease prevalence and population demographics. Of particular concern is the competition for limited colonoscopy resources among average-risk screening program participants, symptomatic or high-risk patients, and the ongoing surveillance requirements for all groups. Failure to understand the effects of operational decisions such as screening test selection, positivity threshold, and follow-up test modality may cause unintended harm, hinder the program's effectiveness, and make inefficient use of limited health care resources. Two-step screening attempts to mitigate the burden on colonoscopy services by requiring a positive stool test before colonoscopy follow-up, however there are many tests available with different abilities to detect true positive and negative cases. A discrete event simulation model, the Simulation of Cancer Outcomes for Planning Exercises (SCOPE) Model, was constructed to compare the effects of various colorectal cancer screening decisions on demand for colonoscopy services, crude colorectal cancer incidence, and cumulative colorectal cancer mortality. Unlike previous screening evaluations, SCOPE considers the effects of competition for constrained colonoscopy services between patient groups on patient and health system outcomes. The study results indicated an increase of 33% to 54% of total colonoscopy services depending on the test selected and the uptake rate. Increased demand for screening follow-up and surveillance colonoscopy services was not offset by modest reductions in disease prevalence and subsequent diagnostic service demand. Failure to provide adequate colonoscopy services reduced the effectiveness of screening. Increasing the FIT positivity threshold reduced the demand for additional average risk screening follow-up colonoscopies by 65%. Screening programs that select a stool test that permits raising the threshold at which a result is considered positive may take advantage of potential benefits of screening without overwhelming colonoscopy services.