Computed tomographic colonography is an acceptable alternative to colonoscopy as a colorectal cancer screening method in average-risk, asymptomatic adults, but gastroenterologists planning to use the technology should undergo more extensive training than previously recommended, according to newly updated standards from the American Gastroenterological Association.
The task force report, "AGA Standards for Gastroenterologists for Performing and Interpreting Diagnostic Computed Tomography Colonography: 2011 Update," is scheduled to appear in the December issue of Gastroenterology.
Perhaps most notable is the AGA’s support of this technology for screening of average-risk asymptomatic adults. This marks a change from 2007, when the original AGA task force statement was published. That statement stopped short of supporting CTC for routine colorectal cancer screening in average-risk asymptomatic patients – the evidence was considered insufficient.
In the update, however, the authors note that "several multidisciplinary groups involved in CRC [colorectal cancer] screening guideline development, including the AGA, have endorsed CT colonography for CRC screening."
Both the 2007 and 2011 versions state that CTC is effective for several specific purposes: evaluation of the colon proximal to an obstructing lesion, and failed colonoscopy with continued need to evaluate the colon. CTC can also be considered in patients who cannot undergo, or choose not to undergo, screening methods other than CTC.
Courtesy Dr. Brooks D. Cash
Dr. Brooks D. Cash
Research conducted in the past few years shows that most of the recent, high-quality published studies on CT colonography indicate that its potential benefits as a primary screening tool in average-risk adults most likely exceed the potential harms, according to the authors, Dr. Brooks D. Cash, AGAF, of Walter Reed National Military Medical Center, Bethesda, Md., and his coauthors.
"Taken as a whole, the updated body of literature examining screening CT colonography demonstrates sensitivity for CRC and adenomas greater than or equal to 6 mm that approaches that of colonoscopy and is superior to results obtained with other methods of screening," they wrote.
Although data on sensitivity of CTC for larger lesions have been consistent, mixed results have been found for smaller lesions, leading to some controversy. The AGA joins groups including the American Cancer Society and the Blue Cross/Blue Shield Technology Evaluation Center, in their support of CTC use for primary screening. CTC has also been endorsed as a primary CRC screening test for average-risk, asymptomatic adults by a multidisciplinary group that includes members of the American Cancer Society, the U.S. Multi-Society Task Force on CRC, and the American College of Radiology.
As for training of gastroenterologists who wish to perform CTC, the AGA standards continue to call for initial training that includes review and interpretation of at least 75 cases with endoscopic correlation, followed by a 6-month preceptorship involving interpretation of at least 150 cases. The 2007 standards had called for a 4- to 6-week preceptorship involving interpretation of at least 25-50 additional cases.
The preceptorship may consist of training with a mentor in person or it "may take place in any of several scenarios (e.g., web-based mentoring)," and the updated standards also call for mastery of new manual skills and didactic information through hands-on individualized instruction by experienced faculty.
"Gastroenterologists training to interpret CT colonography should operate the workstation and review cases in an interactive fashion, whereby they are responsible for the manipulation of the data set. Training requires involvement in the acquisition of studies, which means that at least some of the training must be done at a busy imaging center," they wrote.
The updated standards also note the need for ongoing training and self-assessment, to include formal continuing medical education accredited courses in CT colonography, and the task force emphasizes the importance of collaboration with board-certified radiologists to review extracolonic portions of the CTC exam.
After CTC results are obtained and interpreted, patients with any polyp that is 6 mm or larger, or three or more polyps of any size (in the setting of high diagnostic confidence), need to be referred for consideration of endoscopic polypectomy. The appropriate clinical management of patients with one or two lesions that are 5 mm or smaller is unknown, but such lesions should be reported when diagnostic confidence is high.
Other additions to the updated guidelines include a strong recommendation for participation in the ACR National Radiology Data Registry’s CT Colonography Registry and the AGA Digestive Health Outcomes Registry, and a reminder that gastroenterologists who provide CT or other advanced imaging services, and who bill under Part B of the Medicare Physician Fee Schedule, must be accredited by Jan. 1, 2012, to receive Medicare payment for the technical components of these services.