Virtual Colonoscopy Nears Prime Time
CT Colon Scan Finds Cancer as Well as Colonoscopy
Oct. 3, 2007 - Flying through your colon in virtual reality, Perry Pickhardt, MD, says he can find early colon cancer at least as well as a gastroenterologist using a very real colonoscope.
A new study backs up this boast by comparing colon cancer screening with virtual colonoscopy to screening with real colonoscopy. The study, in healthy, low-risk patients, compared the results of 3,120 consecutive virtual colonoscopies to results from 3,163 real colonoscopies.
"We found slightly more advanced polyps than colonoscopy did, and without any complications," Pickhardt tells WebMD. "The outcomes are not just good, but beyond our expectations. Nobody thought we would find more important things than did colonoscopy -- the current gold standard -- but we have."
Pickhardt, associate professor of radiology at the University of Wisconsin, is a pioneer in the field of virtual colonoscopy. Virtual colonoscopy, more accurately known as CT colonography or CTC, uses special software to view CT scans of a patient's colon. Experts using the technique can see colon polyps before they become deadly colon cancers.
"The reason we are able to find polyps so successfully is we find them on this 3-D reality fly-through," Pickhardt tells WebMD.
Doctors now agree that the best way to find colon polyps is with a colonoscope. But Pickhardt says that's going to change.
"Years from now we will be amazed we did such an invasive test for screening," he says.
Virtual Colonoscopy vs. Real Colonoscopy
The study by Pickhardt, David H. Kim, MD, and colleagues is not a randomized clinical trial. Instead of being randomly assigned to virtual colonoscopy or real colonoscopy, patients chose the screening method they wanted.
But both groups of patients were referred by the same doctors. Most patients in each group had no symptoms of colon cancer and were only at average risk.
The two techniques detected colon cancer at nearly the same rate. They also detected polyps larger than 10 millimeters -- a size considered dangerous -- at the same rate. Colonoscopy found far more tiny polyps than did CTC. But such polyps only very rarely carry cancer cells.
Colonoscopy has one big advantage: Any polyps that are found are immediately removed. Patients who have suspicious polyps found by CTC must undergo colonoscopy to have them removed. This happened to 8% of the patients in the study. Some patients with smaller polyps, however, chose to undergo CTC surveillance to see whether the polyps really were growing into something dangerous.
Seven of the patients who underwent colonoscopy screening had a colon puncture. This happens in about one in 500 colonoscopies and often requires surgical repair. The puncture rate seen in the study was in the expected range. There were no punctures in the CTC group.