Surveillance for colorectal cancer in average-risk patients, familial high-risk groups, and patients with adenomas.

New concepts and technological advances have stimulated a heightened interest in the secondary prevention of colorectal cancer; the identification and eradication of premalignant lesions, and the detection of early cancer before the development of life-threatening consequences. This approach must be selective based on risk factors. Fecal occult blood testing and sigmoidoscopy have been applied to the average-risk patients, whereas x-rays, endoscopy, biopsy, and cytology have been applied to the high-risk groups for case findings and screening. Program results to date are encouraging for average-risk patients. Compliance with fecal occult blood testing and sigmoidoscopy has been high in motivated groups self-selected for entry into screening programs. The rate of positive slides, false-positivity, and predictive value for neoplasia has been acceptable. Dukes' staging of cancers has been favorable. False-negativity and mortality data are not yet available. Flexible sigmoidoscopy has been shown to be an effective substitute for rigid sigmoidoscopy in trained hands. Familial polyposis and Gardner's syndrome families have been well studied, but interest in the nonpolyposis inherited colon cancer families is relatively new. Followup procedures after polypectomy have been variable and only recently has there been an organized attempt to prospectively study the effectiveness of different followup plans. The National Polyp Study has been developed to address this issue.