AJR 2001; 177:975-988.
Ferrucci JT.
Virtual colonoscopy (CT colonography) promises to become a primary method for colorectal cancer screening and return radiologists to a major role in colon cancer prevention. Results from major centers in the United States show accuracy to be comparable to conventional colonoscopy for detection of polyps of significant size—that is, greater than 10 mm—with few false positives. The advent of virtual colonoscopy has also heightened awareness of the natural history of colonic polyps, particularly in terms of identifying an appropriate target size for detection in colorectal screening programs. Small polyps (<10 mm) are often either hyperplastic on histology or are unlikely to progress to frank cancer in the patient’s lifetime and are therefore of little clinical significance for the average adult. Thus, the rationale for detecting and removing each and every colonic polyp regardless of size has come under increasing scrutiny in the context of cost-benefit analysis of various test strategies for colorectal cancer screening. Virtual colonoscopy may allow patients to obtain reliable information about the status of their colonic mucosa noninvasively and thus make a more informed decision as to whether to proceed to conventional colonoscopy for polypectomy.
Current research is directed to improving the speed of image analysis, use of computer-aided methods for polyp detection, MR colonography, and oral contrast tagging of fecal contents to avoid the need for rigorous bowel preparation and thus improve patient compliance.
Radiologists introducing virtual colonoscopy for colon cancer screening should use several strategies: They should create eveidence-based data by conducting well-conceived clinical trials, establish public accountability by developing performance standards and accreditation programs through the American College of Radiology, seek support from advocacy groups dedicated to prevention and cure of colorectal cancer, and foster new paradigms with gastroenterologists for improved colon cancer prevention strategies.