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 chemoprophylaxis in relation to screening.

DESIGN

Markov model.

DATA SOURCES

Literature on colorectal cancer epidemiology, screening, costs, 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 risk 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, screening with FS/FOBT or COLO cost less than $31 000 per life-year gained.

RESULTS OF SENSITIVITY ANALYSIS

Cost-effectiveness estimates depended highly on the magnitude of colorectal cancer risk reduction with aspirin, aspirin-related complication rates, and the screening adherence rate in the population. However, when the model's inputs were varied over wide ranges, aspirin chemoprophylaxis remained generally non-cost-effective for patients who adhere to screening.

CONCLUSIONS

In patients undergoing colorectal cancer screening, aspirin use should not be based on potential chemoprevention. Aspirin chemoprophylaxis alone cannot be considered a substitute for colorectal cancer screening. Public policy should focus on improving screening adherence, even in patients who are already taking aspirin.