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No data to support leaving small colon polyps in place

April 27, 2007

The American Gastroenterological Association (AGA) Institute is eager to increase the number of patients who receive screening for colon cancer. There are a variety of established screening methods that are widely available, and emerging technologies, such as computed tomography colonography (CT colonography), that are under investigation. As the medical community evaluates CT colonography, the AGA Institute offers the following comments regarding the study by Pickhardt et al published in Cancer on the cost-effectiveness of colorectal cancer screening with CT colonography and the impact of not reporting diminutive lesions.

"To date, there are no long-term, adequately controlled studies that define whether leaving small polyps is truly safe. The science is not there, and only anecdotal conclusions can currently be made," says John I. Allen, MD, MBA, AGAF, incoming chair of the AGA Institute Clinical Practice & Quality Management Committee. "We are especially concerned as more literature emerges about small, flat, right-sided polyps. These were traditionally called hyperplastic polyps but now are recognized to be sessile serrated polyps that have a malignant potential. Radiologic imaging would not be expected to detect these polyps. This should remind us all of the need for meticulous evaluation, slow withdrawal and inspection of the proximal colon during optical colonoscopy."

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.

"The need to define the natural history and biological significance of small polyps is central to refining colorectal cancer screening, irrespective of modality," says Joel V. Brill, MD, AGAF, incoming chair of the AGA Institute Practice Management & Economics Committee. "We support any technology that helps more patients get screened for colorectal cancer. However, in the rush to increase screening rates, we cannot lose sight of the importance of providing patient care that is based on evidence. Right now, the data to support leaving small polyps in place is lacking."

CT colonography is an emerging technology that shows promise, but it is not widely available. Medicare and most insurance companies do not cover the test for colon cancer screening. Many practical issues associated with CT colonography still need to be addressed - including standardization of test performance, patient preparation and interpretation of test results - before CT colonography can be recommended for routine clinical practice. If a polyp that needs removal is found during CT colonography, the patient must then undergo a colonoscopy. Some patients might find it more convenient to have a single definitive optical colonoscopy. Additionally, after a patient has a negative colonoscopy, there are studies that show that it is possible to wait for 10 years for subsequent screening. There is no information on whether it is safe to wait 10 years between CT colonographies.

"Patients should not put off screening for colorectal cancer and polyps. All adults should discuss options with their physicians and be certain of their life-time risk for colon cancer. People with a family history that includes colon cancer are at higher risk, as are certain racial and ethnic populations and people with inflammatory bowel disease or previous colon polyps or cancer. By age 50, all adults should undergo one of the colorectal cancer screening tests currently available to them," says Dr. Allen.

Guidelines of multiple agencies and professional societies, including the AGA Institute, underscore the importance of screening for all individuals 50 years of age and older (younger for certain groups known to be at higher risk). Currently, there are several tests that may be used to screen for colorectal cancer, the second-leading cause of cancer deaths in the United States. Recommended tests include colonoscopy, flexible sigmoidoscopy, fecal occult blood test and barium enema.

American Gastroenterological Association