Both real and virtual colonoscopies work: report

By Gene Emery
18 sept 2008--Doctors who perform colonoscopies should not be worried that they may lose business to so-called virtual colonoscopies, despite reports that both approaches work equally well at detecting colon cancer, a gastroenterology expert said on Wednesday.
Details of a study showing both techniques work equally well were published in the New England Journal of Medicine on Wednesday. Partial results had been presented at medical meetings.
Dr. Daniel Johnson of the Mayo Clinic in Scottsdale, Arizona and colleagues did both virtual colonoscopies and standard colonoscopies on 2,500 volunteers. They found that the virtual technique, which uses an X-ray computed tomography or CT scanner, detected 90 percent of precancerous polyps 10 millimeters or larger.
Regular colonoscopies are done by gastroenterologists using a flexible lit tube passed through the bowel. A device on the end can remove polyps for testing right away.
But with a virtual colonoscopy, also known as CT colonography or CTC, there is no sedation, so patients can quickly go back to their normal activities, the cost is significantly lower than a colonoscopy, and there is less risk of the bowel being punctured.
Both require drinking strong laxatives, a major complaint among patients. And if lesions are spotted during a virtual colonoscopy, the patient will require a standard procedure to remove them.
Virtual colonoscopies can also be uncomfortable because they require briefly inflating the bowel with carbon dioxide while the patient lies on a scanner.
"Both techniques are going to miss some lesions, both polyps and cancers," Johnson said in a telephone interview.
"In our study, there was a patient with a 35 millimeter mass that was missed in colonoscopy but found in CT colonography. None of these tests are perfect."
Colorectal cancer kills 52,000 people in the United States each year, according to the American Cancer Society. Most Americans are advised to begin getting regular colonoscopies at age 50.
Only about half of the 70 million Americans at risk for colon cancer are getting screened now, and the choice of CTC may encourage more people to be tested, he said. Gastroenterologists "are nervous that a lot of business will be taken away from them," Johnson said.
But the availability of a noninvasive method "has actually increased our colonoscopy volume," said Dr. Brooks Cash of the American Gastroenterology Association and a gastroenterologist at the National Naval Medical Center in Bethesda, Maryland, where both techniques are used.
That means more people need a follow-up colonoscopy to remove any polyps that could grow into tumors.
Cash estimated that colonoscopies typically account for 50 to 60 percent of a gastroenterologist's income.
"It appears to be a very reasonable, very accurate test for colon cancer screening," he said in a telephone interview. "It will get them (patients) into the store, if you will. Then they can use either test."
Johnson said CTC uses half the radiation of a standard CT scan.