The Evaluation of Cancer Screening: Concepts and Outcome Measures

Cancer screening uses many investigative procedures, and different screening programs and methods have different objectives. For example, mammography aims to detect breast cancer at an earlier stage when successful treatment is more likely, whereas colonoscopy is aimed primarily at detecting adenomas in the colon and removing them, thus preventing them from progressing to cancer at all. Evaluation has different objectives, including proof of principle, checking that screening services are delivering the desired clinical outcome, technical quality control of the investigation procedures. All necessitate a range of tools for evaluation. We review these tools, with particular attention to appropriate outcome measures.