Screening for colorectal cancer.

Screening for cancer is performed in order to detect unsuspected cancers in an asymptomatic population. Screening is justified for the detection of precancer and cancer when the screening test is safe and the disease has a prevalence that justifies the cost and also when testing has low rates of false positive results. Screening can lead to the early diagnosis of specific cancers which, when treated, can result in a prolonged life span. Colorectal cancer is the third-most common form of cancer in the Western world. Many of these cancers are thought to arise from precancerous lesions in the colon, such as adenomatous polyps. The specific advantage of colorectal cancer screening include the earlier detection of such cancers, the detection of benign conditions such as polyps that can predispose to cancer and the potential for earlier and curative therapy in these patients. Screening for colorectal cancer is indicated where life expectantly is greater then five years and, in general, for people under 75 years of age.