TUESDAY, April 13, 2004 (HealthDayNews) -- A computer-assisted screening test for colon cancer is gaining popularity because it is minimally invasive, but a new study has found it isn't yet ready for widespread use.
The researchers discovered the accuracy of the virtual colonoscopy in detecting cancers is substantially lower than that of conventional colonoscopy. And they suggest the use of the technique should be limited until both technology and training are improved.
"The accuracy of this technique was surprising and disappointing," said lead researcher Dr. Peter B. Cotton, director of the Digestive Disease Center at the Medical University of South Carolina.
This study was different from other studies, which found much better accuracy, he added. The goal of this study was to see if regular radiologists could reproduce the results of the other studies. "And the answer was they couldn't," Cotton said.
In past trials, virtual colonoscopy had been found to be reasonably accurate for diagnosing colorectal tumors. However, these studies were done at expert centers, he noted.
Virtual colonoscopy is the examination of computer-generated images of the colon made up of data from an abdominal CT scan. The advantage of the technique is that it is noninvasive and does not require inserting a tube into the colon, as is done in a standard colonoscopy.
In the study, Cotton's team had 615 patients undergo a virtual colonoscopy before having a standard colonoscopy. The researchers then compared the accuracy of both methods in detecting colon polyps.
Virtual colonoscopy found only 39 percent of the polyps that were at least 6 millimeters in size and only 55 percent of the polyps that were at least 10 millimeters in size.
These results were compared with standard colonoscopy, which detected 99 percent of the polyps at least 6 millimeters in size and 100 percent of the polyps that were at least 10 millimeters in size, according to the report in the April 14 issue of the Journal of the American Medical Association.
Based on these findings, Cotton said that "people should think hard before they spend money on a procedure that is not yet proven to be accurate."
Virtual colonoscopy is not covered by most health insurance, Cotton added. "If you read some of the hype, it sounds very attractive, but it's only valuable if it does the job, and our study shows that in the real world it may not do so."
Cotton also noted that even with a virtual colonoscopy, patients have to do the same bowel preparation as done for a standard colonoscopy. This preparation involves not eating solid foods and using laxatives to clean the bowel.
Moreover, with a standard colonoscopy any polyps that are found can be removed during the procedure. If any polyps are found during a virtual colonoscopy, the patient will have to undergo a standard colonoscopy and go through bowel preparation again.
Cotton said virtual colonoscopy "is not ready for prime time now."
The technique shows promise, however. With greater technical improvements in scanners and the software that runs them, coupled with better and more specific training of radiologists, Cotton said virtual colonoscopy will be a valuable addition to the detection of colon cancer.
Cotton stressed that patients with colorectal symptoms should have a colonoscopy, as should anyone over 50 and especially all those with a family history of colon cancer.
Dr. David F. Ransohoff, a professor of medicine at the University of North Carolina, said that, with this report, "virtual colonoscopy looks less good than it did in other studies."
Researchers need to figure out why there are differences in the studies, added Ransohoff, author of an accompanying editorial in the same journal issue.
"In the long run, virtual colonoscopy will be one attractive option for cancer screening, but it needs further development before it is implemented in widespread use," Ransohoff said.
More information
The American Cancer Society has a page on colon cancer, while the National Cancer Institute can tell you more about virtual colonoscopy and other screening methods.
