Virtual colonoscopy, a new, high-tech twist on a standard test to find colon cancer before it shows symptoms, needs improvement, said authors of a new report.

The researchers found that patient comfort must be better in order for virtual colonoscopy to become widely accepted.

"Efforts to improve patient experience during virtual colonoscopy need to be investigated," said Kenneth R. McQuaid, MD, and colleagues in a report in the journal Gastrointestinal Endoscopy (Vol. 54, No. 3).

Colonoscopy is one of best screening tests for colon cancer.

Cancer screening tests are given to those who have some risk of developing a specific cancer yet show no signs of it. The test can find the disease in its early stages when the chances of successful treatment are highest.

During the standard colonoscopy, the patient is drowsy from medication as the doctor passes a very thin, lighted tube with a tiny video lens through the rectum into the colon. The doctor views the inside of the colon on a screen.

Any polyps — pre-cancerous growths — seen during the test can be removed through the colonoscope, preventing them from turning into cancer. An already existing colon cancer can be visualized through the video lens and an appropriate treatment can shortly follow.

In virtual colonoscopy, instead of a tube being inserted into the colon, images from a CT scan (X-ray with many pictures) outside the body show the inside of the colon.

Before either test, the patient cleans the colon by drinking a large amount of a flavored liquid the day before. At the time of the test, the colon is filled with air to make it easier to view inside it.

To learn which test patients preferred, McQuaid and colleagues screened 295 patients, first with virtual colonoscopy and then with conventional colonoscopy, at the San Francisco Veterans Affairs Medical Center.

The patients said they felt more pain, discomfort, and felt less respected during the virtual colonoscopy than during the standard colonoscopy.

Overall, patients said they would rather have a standard procedure than the virtual one, even if it meant waiting almost a month longer for the test.

Bernard Levin, MD, vice president of cancer prevention at M.D. Anderson Cancer Center, said, "There will always be a bias, because one procedure involves sedation which makes it more comfortable." Levin is the chair of the American Cancer Society (ACS) national colorectal cancer roundtable.

According to Durado Brooks, MD, director of prostate and colorectal cancer control for the ACS, virtual colonoscopy is a promising development, but still needs more work.

"Virtual colonoscopy can have a high number of false positives, a showing of a suspicious growth where there really isn't one," said Brooks.

If the virtual test shows what looks like a suspicious growth, it must be followed by standard test to remove any growth truly present, so screening with virtual colonoscopy could prove to be expensive, he added.

And standards haven't been set for how the tests are done and who reads them, Brooks said, so virtual colonoscopy images can be interpreted in different ways.

"This is a very exciting, very promising new technology, but for right now it must still be considered investigational," Brooks said.