Principles of Cancer Screening.

Early detection of cancer, prior to its clinical manifestations, appears to be a worthwhile and desirable goal. Yet, the concept and acceptance of cancer screening remain controversial and often confusing. While the benefits of screening are obvious to those whose screening tests have resulted in successful interventions, attention also needs to be given to the risks, economic costs, and psychological effects of screening procedures. Specific governing principles that define the cancers to be screened, the appropriate screening test, and the measurement of outcomes should be established in order for a screening program to be deemed worthwhile. A beneficial screening strategy detects cancer prior to its systemic spread, alters the natural history of the disease, and defers the time of death.