Screening: potential for cancer prevention.

Cancer screening is the application of a test in large numbers of asymptomatic persons for the early detection of cancer. The objective is to reduce deaths among the population screened. Prerequisites for implementation of cancer screening are sufficient knowledge of the biology of the cancer, an appropriate screening test, an effective intervention, either by removal or with curative treatment, and the decision that the costs are worth the benefits. At this time, screening asymptomatic women for early detection of cancers of the cervix using the Pap test and breast using mammography has the greatest potential for the control of these common cancers.