Study finds virtual colonoscopy not ready for widespread use

By Kimberly Wong

A study by researchers at UCSF Medical Center has found that virtual colonoscopy may not measure up to conventional colonoscopy for widespread colorectal cancer screening in the U.S.

Using a “decision analytic model” that integrates statistical information with sophisticated computer analysis, the research team projected the clinical and economic impact that each screening strategy could have on a national scale. The conventional procedure is currently the most comprehensive tool available for screening, while virtual colonoscopy is a newer technology and is still being refined as a standard screening method.

“The main question of the study was: how good of a test does virtual colonoscopy have to be in order to compete with conventional colonoscopy for widespread implementation?” said Uri Ladabaum, MD, MS, UCSF assistant professor of medicine and lead author of the study that appears in the July issue of Clinical Gastroenterology and Hepatology.

Colon cancer is highly treatable if caught early by screening, yet the number of people who get checked is disappointingly low, according to Ladabaum.

Over the past year, research teams at other institutions conducted two large U.S. studies that reviewed the two colonoscopy procedures, producing conflicting results and discussion by some medical specialists about certain aspects of the study methodology, according to Ladabaum.  One study showed virtual colonoscopy was excellent at detecting abnormalities in the colon, while the other reported less favorable findings. The objective of the UCSF team was to add perspective to these results, he said.  “If the positive results from this recent prominent study could be reproduced widely in the community, virtual colonoscopy might be comparable to conventional colonoscopy.”

Conventional colonoscopy is an invasive procedure that involves inserting a long tube-shaped camera through the length of the colon to look for abnormalities. Virtual colonoscopy is less invasive, involving placement of a small tube in the rectum to inflate the colon and then using a CT scan and imaging software to create two- and three-dimensional images to detect abnormalities.

Patient interest in undergoing virtual colonoscopy has grown because it is less invasive. With virtual colonoscopy—as well as other colon cancer screening tools such as sigmoidoscopy, double-contrast barium enema, and fecal occult blood test—patients with abnormal results must still undergo colonoscopy for the removal of polyps or to biopsy possible cancers, Ladabaum said, and this was factored into the UCSF analysis.

The UCSF researchers also incorporated data from the other two national studies into their analysis along with information from the United States Census to predict outcomes of both screening methods.

In order for virtual colonoscopy to compete with conventional colonoscopy, Ladabaum said several conditions would be required. It would need to perform as well as the conventional procedure at picking up small and large growths called polyps that have the potential to become cancerous and detect nearly all growths that already are cancerous. The test would have to have an acceptably low rate of false-positives, and if results appeared abnormal, the follow-up colonoscopy would have to pick up nearly all of the true lesions found by the virtual test.

Based on their findings, the UCSF researchers conclude that the clinical results that could be expected from virtual colonoscopy as it is currently available to the general community would not be as good as with conventional colonoscopy.

In addition, findings showed that using virtual colonoscopy would cost more. “Even if the two strategies produced the same clinical benefits,” said Ladabaum, “the virtual colonoscopy test would need to cost approximately three-fourths as much as conventional colonoscopy in order for the two strategies to be equally cost-effective.”

Diagnostic colonoscopy costs between $800 and $1,200 and the true cost of virtual colonoscopy has yet to be determined, but current charges are equal or higher.

While some patients may prefer virtual colonoscopy, Ladabaum concludes that it’ s not ready for routine use. He reiterated the recommendations of major national organizations that all persons be screened at age 50 with currently available options, including testing for blood in the stool, sigmoidoscopy or colonoscopy. Those at average risk who choose colonoscopy should have it every 10 years. Even if virtual colonoscopy improves and is accepted in the future, people at above-average risk (such as those with family history of colorectal cancer) should get a colonoscopy.

“If virtual colonoscopy can be perfected, it could be an important screening tool for the appropriate populations,” said Ladabaum. “It may have a major impact if it convinces those who aren’t getting screened to actually undergo screening. Even though technological advancements have been coming along rapidly, virtual colonoscopy is not yet ready for widespread acceptance.”

Other investigators were Kenneth Song, MD, Department of Medicine, UCSF; and A. Mark Fendrick, MD, School of Public Health and Center for Health Outcomes, Innovation, and Cost-Effectiveness Studies, University of Michigan, Ann Arbor.