Screening techniques for prevention and early detection of colorectal cancer in the average-risk population.

Colorectal cancer (CRC) is associated with considerable morbidity and mortality, with more than 1,000,000 new cases and 500,000 deaths occurring annually. CRC has a natural history of transition from normal mucosa through adenoma to malignant lesion that spans, on average, 15 to 20 years, providing a window of opportunity for effective prevention and intervention through routine screening. The optimal screening strategy for the average-risk population aged >/= 50 years remains the subject of debate, however. Endoscopic screening is undoubtedly the most effective screening method, and is also therapeutic since it permits polyp removal. The simplest and best-evaluated available screening method is the fecal occult blood test, which is relatively inexpensive and noninvasive, but less accurate than colonoscopy. This method detects cancer at an early stage but, since precancerous polyps rarely bleed, it is not suitable for disease prevention. Compliance with current screening methods is a major barrier to optimal prevention. Several new screening modalities, such as self-navigating colonoscopes, prepless virtual colonoscopy, and stool genetic testing, may improve compliance. Until these technologies are available or shown to be appropriate for routine screening, however, conventional colonoscopy remains the most efficient method for CRC screening and prevention.