Aspirin as an adjunct to screening for prevention of sporadic colorectal cancer - A cost-effectiveness analysis

Background: Aspirin may decrease colorectal cancer incidence, but its role as an adjunct to or substitute for screening has not been evaluated. Objective: To examine the potential cost-effectiveness of aspirin chemoprop hylaxis in relation to screening. Design: Markov model. Data Sources: Literature on colorectal cancer epidemiology, screening, cost s, and aspirin chemoprevention (1980-1999). Target Population: General U.S. population. Time Horizon: 50 to 80 years of age. Perspective: Third-party payer. Intervention: Aspirin therapy in patients screened with sigmoidoscopy every 5 years and fecal occult blood testing every year (FS/FOBT) or colonoscopy every 10 years (COLO). Outcome Measures: Discounted cost per life-year gained. Results of Base-Case Analysis: When a 30% reduction in colorectal cancer ri sk was assumed, aspirin increased costs and decreased life-years because of related complications as an adjunct to FS/FOBT and cost $149 161 per life- year gained as an adjunct to COLO. In patients already taking aspirin, scre ening with FS/FOBT or COLO cost less than $31 000 per life-year gained. Results of Sensitivity Analysis: cost-effectiveness estimates depended high ly on the magnitude of colorectal cancer risk reduction with aspirin, aspir in-related complication rates, and the screening adherence rate in the popu lation. However, when the model's inputs were varied over wide ranges, aspi rin chemoprophylaxis remained generally non-cost-effective for patients who adhere to screening. Conclusions: in patients undergoing colorectal cancer screening, aspirin us e should not be based on potential chemoprevention. Aspirin chemoprophylaxi s alone cannot be considered a substitute for colorectal cancer screening. Public policy should focus on improving screening adherence, even in patien ts who are already taking aspirin.