Virtual Colonoscopy Raises Issues for Further Study
ASGE Recommends Standard Colonoscopy for Patients

OAK BROOK, Ill., Nov. 26, 2004– The American Society for Gastrointestinal Endoscopy (ASGE) has reacted with caution to claims of the benefits of computed tomography (CT) colonography, also referred to as virtual colonoscopy, compared to standard colonoscopy.

"Standard colonoscopy is still the most accurate test for detection and removal of cancer and pre-cancerous growths (polyps) in the colon," stated David Lieberman, MD, Oregon Health Sciences University, Portland VA Medical Center, Portland, OR. Dr. Lieberman is a past ASGE President and Executive Director of the Clinical Outcome Research Initiative (CORI). He is a noted expert in the area of colon cancer screening.

"Like any medical test, colonoscopy is not perfect, and some polyps may be present, but not detected," Dr. Lieberman explained. "However, most pre-cancerous polyps and virtually all cancers will be detected, and can usually be removed during the examination."

Virtual colonoscopy refers to the use of radiological (x-ray) techniques, including computed tomography (CT) and magnetic resonance imaging (MRI) scanning with computers, to produce pictures or images of the colon. It is "virtual" because the images are produced using radiation and evaluated on a computer screen, while a standard colonoscopy uses a thin, flexible lighted viewing tube (a colonoscope) that is threaded slowly through the colon to examine the lining for polyps.

Both standard and virtual colonoscopy requires a bowel preparation to cleanse the colon. Sedation is routinely used to reduce or eliminate discomfort associated with standard colonoscopy, but patients are not sedated for virtual colonoscopy.

Unlike standard colonoscopy, virtual colonoscopy only provides images of the colon, but does not allow for immediate biopsy or polyp removal at the time of the exam. Some abnormalities detected during virtual colonoscopy will require a standard colonoscopy for confirmation and management.

"The position of the ASGE Technology Assessment Committee is that CT colonography is a rapidly evolving technology with still rather varied results from the most recently published studies," said Bret T. Petersen, MD. Chair of the Technology Assessment Committee and director of endoscopy at the Mayo Clinic in Rochester, Minn. "A single recent study yielded very positive results, while most studies suggest CT colonography still has significant room for development and improvement before it becomes a primary screening tool for colorectal cancer."

Issues concerning virtual colonoscopy include:

• Some studies show that more than half of large polyps are not detected by using virtual colonoscopy. More research is needed to determine the accuracy of the test.
• Currently, bowel prep is required to clean the colon. If the test reveals a polyp, a colonoscopy is usually recommended. In most cases, a patient may need to have one prep for the CT colonography and then a second prep for the standard colonoscopy.
• The safety of repeating CT colonography at frequent intervals has not been studied yet. It is not clear if radiation exposure from multiple exams would be safe.

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in men and women and the second leading cause of cancer-related deaths in the United States and Western Europe. The lifetime risk of developing CRC is approximately 6% of the adult U.S. population and almost half will die as a consequence of CRC.

"Early detection of cancer and, more importantly, the identification and removal of polyps that ultimately could become cancers can decrease the mortality for this disease," stated ASGE President David J. Bjorkman, MD, MSPH, SM (Epid), Dean of the University of Utah School of Medicine.

Dr. Bjorkman said, "More than one in twenty adults will develop colorectal cancer in their lifetime. Many of these cancers can be prevented or cured with screening, such as a colonoscopy. Colonoscopy is safe and accurate when performed by a fully-trained endoscopist."

For more information, contact the ASGE at http://www.askasge.org or call 1-866-305-ASGE.

About ASGE: http://www.asge.org
630-573-0600

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American Society for Gastrointestinal Endoscopy
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