Colorectal cancer is the second leading cause of death among cancers in the United States. Screening for this disease is practical because of its high prevalence, the long asymptomatic phase and the presence of a treatable precancerous lesion. Fecal occult blood testing is simple and inexpensive, and colonoscopy is efficient and thorough. Guidelines have stated that colonoscopy, flexible sigmoidoscopy and fecal occult blood testing are all cost-effective screening alternatives. Newer screening guidelines have been revised to recommend colonoscopy every 10 years instead of every five. Sonnenberg and associates reassessed the cost-effectiveness of screening programs for colorectal cancer using fecal occult blood testing, flexible sigmoidoscopy or colonoscopy as the primary screening method.

The end points included the number of prevented cases of colorectal cancer and the cost per one life-year saved from cancer-related mortality. The three screening procedures were compared using computer models based on a Markov process that considered compliance, outcome activities, cost, potential complications and false results, and follow-up procedures. The development of colorectal cancer at any stage of the model was based on age-specific incidence rates. All procedures and diagnostic services were assigned a code to identify the cost for each health care resource used.

Screening with fecal occult blood testing prevented 16 percent of all colorectal cancers compared with prevention rates of 34 and 75 percent with flexible sigmoidoscopy and colonoscopy, respectively. The total cost of managing colorectal cancer increased from no screening (the least expensive) to fecal occult blood testing, to colonoscopy and then to flexible sigmoidoscopy (the most expensive). Colonoscopy once every 10 years was demonstrated to be a cost-effective method of screening compared with the next best alternative, fecal occult blood testing, which costs less but saves fewer life-years. A screening strategy based on flexible sigmoidoscopy every five to 10 years is less cost-effective than either of the other screening methods.

The authors conclude that one colonoscopy every 10 years represents a cost-effective screening test for colorectal cancer and may be the most cost-effective technique. It reduces mortality at a relatively low incremental cost. In addition, this schedule of testing is less likely to be affected by the low compliance rates associated with screening using fecal occult blood testing.