Office-Based Testing for Fecal Occult Blood: Do Only in Case of Emergency

Colorectal cancer is an important source of cancer mortality, ranking a close second behind lung cancer among types of cancer that affect both men and women (1). We know many details of the natural history and biology of colorectal cancer. We know that the gradual transition from small benign polyp to invasive malignancy takes several years, and molecular biologists have traced the accumulation of mutations that drive these changes. We know that we can reduce a healthy person's risk for death from colorectal cancer by inspecting the colonic mucosa and removing polyps and cancer. The proof of this principle is the association of screening sigmoidoscopy and reduced rates of death from cancer originating from the mucosa within reach of the sigmoidoscope, but not beyond it (2). It follows that screening colonoscopy should reduce deaths from cancer arising anywhere in the colon, but we have not proved that point conclusively. Several randomized trials have shown that the fecal occult blood test (FOBT) reduces the risk for death from colorectal cancer. In the trial with the longest follow-up, the 18-year colorectal cancer death rate was 14.1 deaths per 1000 patients with usual care and 9.5 deaths per 1000 patients with yearly FOBT (3).

We also know that the death rate from colorectal cancer has dropped steadily from 29 per 100 000 in 1973 to 20 per 100 000 in 2001 (4). However, we do not know why the rate of decline has been constant over this period, rather than dropping more rapidly in the 10 years since the reports of the effectiveness of screening first became available. Low screening rates are one possible explanation. The most recent U.S. Preventive Services Task Force recommendations for average-risk persons age 50 years or older call for annual FOBT and either flexible sigmoidoscopy (every …