Screening for cancer. Useful despite its limitations.

Effective primary prevention strategies are currently available for only a limited number of types of malignant neoplasms. In the meantime, the most effective intervention for cancer control is screening for the early detection of cancer in otherwise asymptomatic persons. Screening is probably most useful for cancers wherein the stage at diagnosis is clearly related to curability. Early detection by screening has been shown to lead to a better outcome following the treatment of cancers of the breast, cervix, and colon. Screening for cancer also enables preneoplastic states to be detected and treated. Screening programs offer an opportunity to enhance the potential of chemoprevention. New cancer screening tests will soon be developed, including some that will detect known genetic predispositions to cancer. Each new screening test must be critically evaluated in rigorous studies before being embraced or rejected by clinicians and patients. In particular, screening efficacy must be demonstrated as judged by improved survival of those screened.