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3-D virtual colonoscopy is more sensitive than colonoscopy
Source: (cancerfacts.com)
Monday, December 01, 2003
CHICAGO – Dec. 1, 2003 – A new computer assisted imaging technique may soon offer an alternative to colonoscopy in screening people for colon cancer, say researchers.
The newer technique, called three-dimensional computed tomography (CT) colonography, also known as virtual colonoscopy, is more sensitive and less invasive than conventional colonoscopy in screening average-risk patients.
A research team led by Dr. Perry J. Pickhardt presented its findings today at the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
"I believe virtual colonoscopy will eventually join conventional colonoscopy as a major component of colorectal cancer screening in the U.S.," Pickhardt said in a prepared statement.
The new technology allows radiologists to obtain 3-D images from different angles, providing a "movie" of the interior of the colon, showing doctors whether polyps are present and where they are located.
Colon polyps are benign growths that may develop into colon cancer if not removed. Many people resist screening because of the discomfort caused by conventional colonoscopy and other tests, which require that a doctor snake a long optical device through the anus, rectum and intestines to look for polyps.
The new multicenter trial was conducted at the National Naval Medical Centers in Bethesda, Md., the Naval Medical Center in San Diego, and at Walter Reed Army Medical Center (Walter Reed) in Washington, D.C.
For this study, lead-author Pickhardt, co-author Lieutenant Colonel Dr. J. Richard Choi, and colleagues performed both conventional and virtual colonoscopy on 1,233 asymptomatic adults, 97.4 percent of whom were at average risk of having colonic polyps.
Overall, virtual colonoscopy detected more than 92.6 percent of significant polyps. 8 mm and larger, whereas conventional colonoscopy detected 89.5 percent of such polyps. Two malignant polyps were present, and virtual colonoscopy detected both of them, while conventional colonoscopy missed one.
Most polyps missed by virtual colonoscopy were small (5 mm or less) and of little or no clinical importance.
"The goal of screening with virtual colonoscopy is to increase the number of patients that would participate," said Choi, who is the principal investigator of the Virtual Colonoscopy Screening Project at Walter Reed. "Even though colorectal cancer is the second leading cause of cancer death and is almost always preventable, less than half of eligible patients undergo any form of screening."
In recent years, radiologists have begun using CT colonography to screen for colon polyps. Although less invasive, until now the procedure primarily used 2-D CT slices (images) for polyp detection, which are less sensitive.
With the addition of 3-D images, virtual colonoscopy provides the complete picture, creating precise and detailed images of the interior of the colon in a minimally invasive manner.
With virtual colonoscopy, there is no risk of bleeding or of perforating the colon. There is no need for intravenous sedation, and the procedure is less costly than conventional colonoscopy. It also is more convenient, taking 15 minutes or less, because patients need not recover from sedation.
Virtual colonoscopy has the added advantage of allowing doctors to see beyond the inner lining of the colon to the muscular layer and the colon's outer surface. This allows checking for evidence of enlarged lymph nodes around the colon, which may indicate advanced, more invasive forms of cancer.
"The findings of this study should establish virtual colonoscopy as a viable screening option," said Pickhardt, who is an associate professor of radiology at University of Wisconsin Medical School in Madison. "This less invasive screening option will likely encourage more adults to seek testing, resulting in many additional lives saved."
A recent commentary in the Journal of the American Medical Association (JAMA) advised that colon screening with any test is recommended for anyone over the age of 50.
According to Choi, as a result of this study, Walter Reed is now offering virtual colonoscopy as an alternative to conventional colonoscopy screening.
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