Screening for colorectal cancer.

Colorectal cancer is a good candidate for secondary prevention strategies. It appears to have a long lead time since most, if not all, of these cancers arise from premalignant adenomas, and several screening methods are available that might detect the cancer in a very early stage. However, there is little evidence at present to show that the available methods of early detection will actually decrease the mortality from colorectal cancer of a screened population as compared to a non-screened population. Studies that might convincingly provide this evidence are still in progress. This paper critically reviews the natural history of colorectal cancer, risk factors, screening trials and treatment.