Standard colonoscopy is still the best way to find colon cancer and the growths that could become cancer, researchers report in the Dec. 17 online edition of the Lancet.

Doctors at Duke University Medical Center compared regular colonoscopy with 2 less invasive procedures: the double-contrast barium enema and "virtual" colonoscopy, a computer-generated image of the colon. They gave each test to 614 people at high risk for developing colon cancer.

Standard colonoscopy did a better job than either of the other tests at finding problems in the colon. It found 98% of the growths (polyps) that were 10 millimeters wide or larger, and 99% of growths 6mm-9mm. Virtual colonoscopy found 59% of larger polyps and 51% of smaller ones, while barium enema found 48% of the large growths and just 35% of the smaller ones.

Doctors have long known that a barium enema is not as accurate as colonoscopy, said Durado Brooks, MD, director of prostate and colorectal cancers for the American Cancer Society.

"Overall numbers of barium enemas have fallen off dramatically in the last decade," he said. "And since colonoscopy also provides the ability to biopsy or remove lesions, when given the choice, the vast majority of providers have opted to send their patients for colonoscopy, if it was available."

Barium enema is one of the methods ACS lists in its guidelines for colon cancer screening, but Brooks said in most practice settings, the procedure is now mainly used when a person can't undergo a colonoscopy or doesn't have access to one.

ACS does not presently recommend virtual colonoscopy for colon cancer screening because it is not yet clear that the procedure is as effective as traditional methods. So far, studies comparing virtual and standard colonoscopy have had mixed results. One major study found virtual colonoscopy was just as good as standard colonoscopy, while another found it to be inferior.

However, the technology used for virtual colonoscopy is improving, the Duke researchers said. And other studies have found that results depend on the way the scan is analyzed and the experience of the doctors who do it.

"This information, along with the results of many other studies looking at colonoscopy and virtual colonoscopy, will all be weighed as part of our screening guidelines review process in the upcoming year," Brooks said.