, Volume 4, Issue 1, pp 24-33
Date: 31 Jan 2008

Noninvasive diagnostic modalities for early detection of colorectal cancer

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Abstract

Colorectal cancer (CRC) screening strategies currently approved are colonoscopy every 10 years, annual fecal occult blood testing (FOBT), flexible sigmoidoscopy every 5 years, annual FOBT plus flexible sigmoidoscopy, and double-contrast barium enema every 5 years. Colonoscopy has been shown to be preferable, but it is invasive, needs bowel preparation, entails a risk of perforation, and is highly operator-dependent. Several noninvasive strategies are being developed as alternatives to colonoscopy. CT colonography (CTC), also known as virtual colonoscopy, has widely variable results but has been shown to have acceptable cost-effectiveness at either 5-year or 10-year intervals, whether it is performed using two-dimensional or three-dimensional techniques. Fecal immunochemical tests have now been shown to have clearly superior performance compared with guaiac-based testing and may become the FOBT of choice. Stool DNA (sDNA) testing has been improved by the addition to the commercial assay of gel-based DNA capture and buffering solutions for DNA stabilization. Simplified sDNA assays (for vimentin methylation and long DNA only) may also improve sensitivity. Advances in our understanding of the molecular genetic changes involved in neoplastic transformation have led to new noninvasive methods to detect tumors. The future of CRC screening will be driven by the performance characteristics of these technologies, which will be more clearly understood as additional data emerge.