the American Gastroenterological Association (AGA) journal Gastroenterology, publish studies analyzing whether CT colonography ("virtual colonoscopy") is ready for clinical practice.

The conclusion of the AGA, the world's largest medical specialty society dedicated to the science and practice of digestive health medicine: Virtual colonoscopy shows significant promise as a colorectal cancer screening option, though many issues need to be addressed before it is recommended for widespread use.

AGA member David Lieberman, MD, who writes an editorial on the study that will be published in the Sept. 7 issue of Annals of Internal Medicine, and an AGA Future Trends report published in the Sept. 1 issue of Gastroenterology, outline specific issues surrounding virtual colonoscopy that must be addressed. Two key issues:

-- Can the high detection rate of cancer and polyps (possible precancerous lesions) achieved by virtual colonoscopy in controlled studies in the hands of experts be reproduced in diverse clinical practice settings? The scans in the Annals study were conducted with state-of-the-art virtual colonoscopy that allows physicians to reconstruct a 3D image of the colon. The scans were conducted and interpreted by expert physicians. In the typical American clinical setting, this technology and expertise is not yet available. Practical issues, including standardization of test performance and interpretation of test results, must be addressed.

-- Because colon polyps can't be removed during a non-invasive virtual colonoscopy, patients with polyps found during the procedure must subsequently undergo a colonoscopy for polyp removal. Very small polyps (<1 cm) are often found during screening, and it is currently unknown whether these growths will develop into cancer. What polyp size, if any, would physicians and more importantly their patients, allow to remain in place and undergo surveillance rather than immediate removal? How will the potential necessity of multiple procedures to detect and remove polyps affect health-care costs? Could frequent surveillance of polyps with virtual colonoscopy expose patients to an unhealthy level of radiation, thereby raising cancer risk?

Gastroenterologists and colorectal cancer-detection experts available for comment on issues associated with virtual colonoscopy are:

-- Emmet B. Keeffe, MD, president of the AGA

-- David Lieberman, MD, AGA member, author of editorial on virtual colonoscopy that will be published in the Sept. 7 issue of Annals of Internal Medicine.