Finding cancer in asymptomatic people. Estimating the benefits, costs and risks.

There are no absolute criteria for determining the effect of early detection on cancer mortality, and evidence from many sources must be examined. The best evidence is provided by randomized controlled trials that use mortality as an endpoint (RCTMs), but this type of evidence is available for only two cancers, i.e., of the breast and colon. The decision to recommend a test for a particular person must take into account the strength of the evidence that early detection reduces mortality, the expected amount of the reduction, the chance the person will ever get the cancer, and the anticipated costs and risks. This paper describes the evidence that early detection of various cancers reduces mortality, and estimates the expected reduction in mortality to be achieved by various tests. Three specific examples are discussed: breast self-examination, mammography in women younger than age 50 years, and chest x-rays for male smokers over age 40.