It is generally believed that the earlier cancer is detected, the better is the chance of achieving a cure. For this reason, considerable attention has been paid to the problem of cancer screening. A primary objective of any screening program is to maximize the preventative effect, while minimizing the effort expended.
Screening is defined as the application of tests or examinations to apparently well persons in order to sort out those who probably have a disease from those who probably do not (4:1776). It involves the application of tests or procedures to people who are apparently in good health. Once screening has determined which people are at greater risk for a given disease, then a diagnostic workup can determine whether or not they actually have it.
A number of criteria need to be met before any particular disease merits routine screening of large numbers of asymptomatic individuals (5:589). For one, the disorder should be serious. Its occurrence should have major health consequences for the population as a whole.
In addition, the disease should also have a preclinical early stage which can be clearly recognized. In general, the longer that this preclinical phase persists in a particular disease, the greater will be the opportunity for the condition's detection (3:413).
Lastly, the third qualification for screening is that the recognition of this preclinical early stage should also result in a reduction of the disease's mortality. This is the ultimate goal of screening: to reduce the complications and mortality rate among the persons screened. There is no point in expending considerable effort to screen for a disease which can be treated just as successfully after its symptoms have appeared. Conversely, it would also be unreasonable to screen for disorders which are untreatable regardless of when they are detected.
Many forms of cancer meet these three screening criteria. In the United...