Screening Sigmoidoscopy: Can the Road to Colonoscopy Be Less Traveled?

Since 1997, there has been a consensus that screening is effective in reducing colorectal cancer mortality and is cost-effective (1-4). Colorectal cancer screening has now become the standard of medical practice, and failure to screen has become a basis for malpractice suits. Guidelines suggest a 1- or a 2-stage screening approach. The 1-stage approach is to screen average-risk men and women with colonoscopy every 10 years. This “1-stop shopping” strategy can screen, diagnose, and treat by removing premalignant adenomatous polyps. The 2-stage approach requires people to have an annual fecal occult blood test (FOBT), flexible sigmoidoscopy every 5 years, or both, followed by colonoscopy if the FOBT result is positive or a polyp is present on sigmoidoscopy. More sensitive guaiac-based FOBTs, newer immunochemical FOBTs (5), and a test for stool DNA mutations have expanded available options for detecting neoplasia. Virtual colonoscopy detects polyps or cancer by reconstructing computed tomographic images (1).

Regardless of the screening method, all roads lead to fiberoptic colonoscopy. A major policy question is whether we have the resources to screen the general population with colonoscopy or whether we should encourage the 2-stage approach, which would spare most people the cost, risk, and inconvenience of colonoscopy. The 2-stage approach would make the road to colonoscopy less traveled. Flexible sigmoidoscopy has a valid place in the 2-stage approach. High-quality case–control studies have demonstrated a 60% reduction in mortality from cancer occurring in the area examined by the sigmoidoscope. A small randomized trial showed that flexible sigmoidoscopy reduces cancer incidence by 80% if polyp detection is followed by colonoscopy and polypectomy (1-4).

The short reach of the flexible sigmoidoscope necessarily limits its accuracy as a screening test for colonic neoplasia. The challenge for the physician …