Research news from the AGA

10/25/04

Studies address heavily-debated issues surrounding virtual colonoscopy

Bethesda, Maryland (Nov. 1, 2004) – Two studies published today show that widespread use of virtual colonoscopy will ultimately decrease demand for traditional colonoscopy and increase colorectal cancer screening rates, and "prepless" virtual colonoscopy is as effective as the traditional method of colorectal cancer screening. These studies were published in the American Gastroenterological Association (AGA) journal Gastroenterology.

Colorectal cancer is the second-leading cause of cancer deaths in the United States. Guidelines of multiple agencies and professional societies underscore the importance of colorectal cancer screening for all individuals 50 years of age and older.

Virtual Colonoscopy for Colorectal Cancer Screening Reduces the Number of Traditional Colonoscopies, Researchers Say
(The Impact of CT Colonography on Colonoscopy Demand, Hur et al.)

Some researchers have argued that the widespread use of virtual colonoscopy will lead to an increase in the total number of traditional colonoscopies performed each year, as traditional colonoscopies are necessary to further study the polyps found in patients undergoing the virtual process. However, in this month's issue of Gastroenterology, Harvard researchers say that increased use of virtual colonoscopy will instead lead to a decrease in the number of traditional colonoscopies.

Results of this study suggest that the number of colonoscopies reported could be reduced by 28 percent if virtual colonoscopy was widely implemented. In a previous analysis by the AGA, virtual colonoscopy was found to be a promising treatment with limitations, such as the inability to consistently detect flat polyps or those smaller than one centimeter.

The Harvard study's projected decrease in traditional colonoscopies varied depending on the polyp size "threshold" or the size polyp used to qualify a patient for a follow-up colonoscopy--a larger polyp threshold results in fewer patients being referred for follow-up traditional colonoscopies. This effect is seen mainly because the percentage of people being falsely referred for further screening decreases with a larger polyp threshold.

"The polyp-size threshold is very important when determining who will be required to undergo additional testing for colon cancer," said Chin Hur, MD, MPH, lead study author. "This study underscores the importance of determining what size polyp is clinically significant and warrants further research."

Currently, colorectal screening compliance in the United States among adults ages 50 and older is 40 percent--a figure that could increase to as much as 55 percent upon full implementation of the screening method. However, mass implementation of virtual colonoscopy for colorectal cancer screening is limited by several factors, including the lack of clinical data that proves its efficacy, continued evolution of technology, the fact that the procedure is not reimbursable by insurance and the continued need for bowel preparation.

Researchers: Bowel Preparation Unnecessary with Virtual Colonoscopy
(CT Colonography Without Cathartic Preparation, Iannaccone, et al.)

Another study published in this month's Gastroenterology addresses the purgative bowel preparation process that's necessary before colonoscopies and its impact on patient compliance. This study found virtual colonoscopy without bowel preparation or substantial dietary restrictions to be as effective as traditional colonoscopy (with bowel preparation) in detecting colorectal polyps.

"The elimination of purgative bowel preparation makes virtual colonoscopy a patient-friendly diagnostic test for colorectal cancer," said Riccardo Iannaccone, MD, lead study author. "We hope that the new prepless test will increase rates of screening and early detection for this cancer killer."

If confirmed by other studies, the researchers from this study believe the findings will drive interest in "prepless" procedures and increase virtual colonoscopy's future standing as a viable and perhaps primary screening method for colorectal cancer. On the basis of its high patient compliance, prepless virtual colonoscopy may ultimately increase the total number of patients being screened for colorectal cancer--a current goal of most physicians.

In this study, patients were asked to drink an iodinated contrast agent diluted in water to "tag" fecal matter prior to the procedure. The purpose of this substance is to provide a way for the professional performing the procedure to distinguish solid and liquid fecal matter from potentially cancerous polyps. Nearly 90 percent of the study participants preferred the fecal tagging regimen prior to virtual colonoscopy over the purgative bowel preparation prior to traditional colonoscopy. Researchers concluded that the use of the tagging strategy, state-of-the-art screening equipment and highly-skilled radiologists contributed to the high ability of the test to detect polyps.

About the Studies

The Impact of CT Colonography on Colonoscopy Demand, Hur et al. Researchers at Harvard Medical School conducted a base-case analysis using estimates from published literature, the Clinical Outcomes Research Initiative (CORI) national endoscopic database and from the Massachusetts General Hospital's endoscopy unit. Current national colonoscopy practice, estimated using various published reports, was used as the foundation to project colonoscopy demand if virtual colonoscopy was implemented as the primary colorectal cancer screening method.

CT Colonography Without Cathartic Preparation, Iannaccone, et al. Researchers from the University of Rome conducted a prospective cohort study on 203 patients 35 years of age or older who underwent low-dose virtual colonoscopy without bowel preparation, and later underwent traditional colonoscopy. The study population consisted of patients who were symptomatic and asymptomatic (48 and 52 percent, respectively). Findings of this study need to be confirmed in a large asymptomatic, average-risk screening population.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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