[Colorectal cancer: prevention and screening].

At present, colorectal carcinoma is one of the few types of cancer for which it is possible to carry out both primary and secondary prevention. Primary prevention involves following a correct diet and maintaining a healthy lifestyle. Secondary prevention includes carrying out appropriate diagnostic examinations on subjects at risk for this type of cancer. Randomized trials, cohort and case-control studies have demonstrated that mortality due to colorectal carcinoma decreases significantly when these screening tests are done. They include testing for fecal occult blood (if annual mortality reduction ranges from 25 to 33%), sigmoidoscopy (case-control studies have shown that this technique can reduce mortality by 60-80%), colonoscopy, and the double-contrast barium enema. Total effectiveness increases when these tests are used in combination. This review synthetically illustrates current knowledge of risk factors and the molecular genetics of colorectal cancer. It offers indications for primary prevention, investigates the effectiveness of each screening test used in secondary prevention, and presents the most highly accredited guidelines for surveillance of the at-risk population.