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AGA Institute statement on CT colonography study

October 08, 2007

Colorectal cancer is the second-leading cause of cancer deaths, affecting both men and women nearly equally and is one of the most preventable cancers. The American Gastroenterological Association (AGA) Institute supports clinically proven technologies that increase the number of patients screened for colon cancer.

The AGA Institute offers the following comments on the study by Kim et al., "CT Colonography Versus Colonoscopy for the Detection of Advanced Neoplasia," published in the Oct. 4, 2007, issue of the New England Journal of Medicine.

"This study expands our knowledge about computerized tomographic colonography (CTC), or virtual colonoscopy," said Robert Sandler, MD, MPH, AGAF, president-elect of the AGA Institute. "The AGA Institute welcomes research that will help to clarify the role CT colonography will play in the screening and detection of colorectal cancer and polyps, but many questions remain. This study by Kim and colleagues shows that CT colonography may be another tool in encouraging patients who have not already done so to get screened for colon cancer."

When a polyp is found during an optical colonoscopy, the physician can remove it immediately. In the study by Kim, diminutive polyps (<5 mm) were not deemed dangerous enough for removal. There are no long-term, adequately controlled studies that define whether leaving small polyps is safe. The AGA Institute recommends that all patients with diagnosed polyps, regardless of size, should be referred for optical colonoscopy.

"Fortunately, small polyps often aren't cancerous - but some are," said Don Rockey, MD, AGAF, chair of the AGA Institute Task Force on CT Colonography. "If patients are comfortable not having small polyps removed, then CTC might be the test for them. Those who want to have their polyps removed - all of them, not just the big ones - might choose optical colonoscopy. Since the natural history of small polyps is not fully understood, the AGA has asked the National Institutes of Health to pursue a study to establish the clinical significance of diminutive polyps (<5mm) using adequate controls and long term follow up. We clearly need data that provides physicians with information on the natural history of polyps and guidance on their management."

According to recommendations put forth in September by the AGA Institute Task Force on CT Colonography:

* 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.

Colon cancer screening rates in eligible populations remain low. The AGA Institute supports all clinically proven options for colon cancer screening and encourages patients to discuss them with their physicians.

American Gastroenterological Association