Occult Blood Testing for Colorectal Cancer

Abstract

Colorectal cancer has long been the target of efforts aimed at early detection. It is the second most common cancer in the United States, with 140,000 new cases and 60,000 deaths estimated to have occurred in 1987.¹ Uncommon in individuals under 50, its incidence increases sharply thereafter.² Investigations into the causes of colorectal cancer have not yet yielded a consensus strategy for prevention. However, early treatment is generally acknowledged to be more beneficial than late treatment. Early detection thus seems to be a reasonable approach to lowering the toll of this cancer.

In the quest for detection of colorectal cancer in the pre-symptomatic stage, two considerations have prompted evaluation of screening methods other than the traditional digital rectal examination. First, polyps and cancers tend to occur more proximally than was once the case. Second, technical modifications have improved the diagnostic capability of endoscopy. The detailed assessments of occult blood screening and sigmoidoscopy in the next two chapters show that as screening methods, both have important shortcomings. For the moment, the form and frequency of screening procedures should be governed by assessment of risk factors in the individual patient.