Despite the fact that CT colonography has not yet been endorsed as a primary screening test in asymptomatic, normal risk adults, many patients have shown interest in this test. The indications for CT colonography are controversial, with many payers recommending that this test only be indicated for patients who have had a failed optical colonoscopy or who have a mass obstructing the colon where examination of the entire colon is required prior to surgical resection. Nonetheless, CT colonography may be considered for patients unwilling to undergo other colorectal screening tests, note the authors of the standards paper, which is published in Gastroenterology, the official journal of the AGA Institute.
"Because of our specialized training, gastroenterologists are experts in CRC screening and colorectal disease. It follows that if patients want a 'virtual colonoscopy' it may be highly appropriate to see a qualified gastroenterologist for the test," notes Don Rockey, MD, AGAF, chair of the AGA Institute Task Force on CT Colonography. "As CT colonography technology is evolving, it is important to check that your physician has been properly trained to ensure that the test is performed and interpreted accurately."
After formal training, during which at least 75 tests should be interpreted, the AGA Institute Task Force on CT Colonography, which authored the standards paper, recommends that gastroenterologists should participate in a mentored CT colonography preceptorship with the candidate physically present and involved in the interpretation of at least 25-50 additional cases. In addition, it is expected that those performing CT colonography will undertake ongoing training and self assessment including attending formal continuing medical education-accredited courses in CT colonography.
The AGA Institute Task Force on CT Colonography offers the following recommendations. The full recommendations are available in the September issue of Gastroenterology.
Any polyp > 6 mm in size (i.e., widest diameter) should be reported and the patient referred for consideration of endoscopic polypectomy. Patients with three or more polyps of any size in the setting of high diagnostic confidence should be referred for consideration of endoscopic polypectomy.
The appropriate clinical management of patients with one to two lesions no greater than 5 mm in diameter is unknown. In the absence of data, the follow-up interval recommended for these patients should be based on individual characteristics of the patient and procedure.
Quality Control and Safety
Practices offering CT colonography should establish a technical quality control program. Endoscopic results in patients referred from CT colonography to endoscopy, including true positive and false negative rates, should be tracked.
Split interpretations of CT colonography are feasible. Gastroenterologists and radiologists performing split interpretations should dictate and sign separate procedure reports that clearly state the specific services they performed related to CT colonography.
Exam and Equipment Specifications
CT colonography should be performed using multidetector CT protocols with high spatial resolution. Computer workstations for dedicated CT colonography interpretation should permit 2D and 3D correlation and visualization of the colonic lumen. CT colonography images should be archived for later comparison. Primary 2D or primary 3D review of the endoluminal surface of the colon and rectum is required.
Guidelines from multiple agencies and professional societies, including the AGA Institute, underscore the importance of colorectal cancer screening for all individuals 50 years of age and older (younger for certain groups known to be at higher risk). The U.S. Preventive Services Task Force, the U.S. Multi-Specialty Task Force, and others have published recommendations for screening for colorectal cancer, the second-leading cause of cancer deaths in the United States. Currently, recommended screening tests include colonoscopy, flexible sigmoidoscopy, barium enema, and fecal occult blood tests.
The AGA Institute formed the CT Colonography Task Force to develop minimum training standards for gastroenterologists in order to provide guidance, and to ensure minimum training competencies are upheld for the performance of the exam. The AGA Institute continues to monitor CT colonography along with other potential colorectal cancer screening tests, and will continue to develop guidance tools and reports as appropriate. The AGA Institute will host a course on CT colonography for gastroenterologists on March 7-8, 2008, in Washington, DC. Additional information will be available this fall.