Colorectal cancer screening

Colorectal cancer occurs throughout the world. Little is known about the etiology of this disease, however, adequate data exist to recommend secondary prevention with mass screening of average risk asymptomatic people age 50 or over. Three randomized controlled trials of a guaiac test for fecal occult blood involving over 250,000 participants found significant reductions in colorectal cancer mortality from both annual and biennial screening. Results from observational studies are consistent with the results from the randomized trials. Therefore, a screening recommendation for a fecal occult blood testing can be justified based on the overwhelming scientific evidence. A compelling argument can be made to use an immunochemical rather than guaiac test, since data suggests that immunochemical tests may be more sensitive and more specific than guaiac tests. Colorectal cancer mortality reductions of at least 33% can be attained with annual fecal occult blood testing. Biennial screening will result in reductions of at least 15 to 20%. There is insufficient evidence to justify either flexible sigmoidoscopy or colonoscopy for mass screening of an average-risk asymptotic population. However, there is justification for colonoscopic evaluation of highrisk members of the population.