Screening for colorectal cancer: an overview.

The critical issue of whether to screen asymptomatic patients for colorectal cancer is related to expected benefits, the population at risk, sensitivity and specificity of available screening and diagnostic tests, cost-effectiveness, and patient compliance. Current screening programs in progress strongly suggest a survival benefit to those patients with a positive screening test but longer follow-up is necessary. Risk factors within the population have been defined, but further work is needed to identify more completely the high-risk subgroups for selective screening. Selective screening of high risk groups would be more productive than mass screening of standard risk patients. Screening and diagnostic tests in current use appear to be sensitive and specific, but more data will have to be examined. Screening with fecal occult testing has been shown to be feasible and productive, but cost-effectiveness must be demonstrated. Patient compliance has been high in well-motivated patients entering studies, but factors involved in health belief must be evaluated as a basis for patient orientation toward screening. Our goal for colorectal cancer is primary prevention--identification and elimination of environmental factors. Until then, secondary prevention may be a realistic achievement--the identification and eradication of precursor lesions and the diagnosis of early colon cancer.