Virtual colonoscopy offers alternative to endoscopy

Virtual colonoscopy is as effective as optical colonoscopy when screening for colorectal cancer, according to a study scheduled for publication in the November issue of the journal Radiology.

The study, conducted at the University of Wisconsin in Madison, found CT colonography to be highly accurate, resulting in a low incidence of follow-up with optical colonoscopy. This led researchers to conclude that, when covered by third-party payers, virtual colonoscopy may entice more people to undergo screening for colon cancer.

"Our positive experience with virtual colonoscopy screening covered by health insurance demonstrates its enormous potential for increasing compliance for colorectal cancer prevention and screening," said Dr. Perry J. Pickhardt, lead author of the paper and an associate professor of radiology at the university. "In addition, recent technical improvements have resulted in even better performance results."

In April 2004, local third-party insurance coverage was initiated in the Madison area for virtual colonoscopy screening. Over one year, researchers performed virtual colonoscopy screening exams on 1110 asymptomatic adults: 585 women and 525 men with a mean age of 58.1 years.

Large (10 mm or larger) colorectal polyps were identified in 43 patients (3.9%). Medium-sized lesions (6 mm to 9 mm) were identified in 77 patients (6.9%). Those without polyps 6 mm or larger were advised to obtain a follow-up screening exam in five years. Most patients with medium-sized lesions chose to undergo follow-up with optical colonoscopy. If all the patients with either a polyp larger than 6 mm or a nondiagnostic segment had undergone subsequent optical colonoscopy, the maximum referral rate would have been 11.9%, according to the researchers.

Sixty-one of the 71 patients who underwent subsequent optical colonoscopy had the procedure performed on the same day as virtual colonoscopy so as to avoid the need for repeat bowel preparation. The optical colonoscopy findings agreed with the virtual colonoscopy findings in 65 of the 71 patients.

"In our experience, providing a less invasive, yet equally effective screening option like virtual colonoscopy has drawn many adults off the sidelines," Pickhardt said. "Since colorectal cancer is uniquely preventable, widespread virtual colonoscopy screening could lead to a significant reduction in mortality from this disease."

Virtual colonoscopy is less invasive than optical colonoscopy, improving patient comfort and reducing risk, he said. Its 3D fly-through images are generated without the insertion of a scope, thereby eliminating the risk of bleeding or tissue perforation. Intravenous sedation is not needed as it is for colonoscopy. The CT-based procedure is also less costly than conventional colonoscopy, and more convenient, as a CT scan typically takes 10 minutes or less.

The positive clinical results of this study in the context of other advantages of CT colonoscopy will lead to further acceptance from the medical community, according to Pickhardt, who predicts national insurance coverage could be put into place within the next one to two years.

"Our goal is not to take patients away from existing strategies like optical colonoscopy, but rather to attract those who are currently not being screened at all," Pickhardt said. "Virtual colonoscopy at our institution is safer, faster, less costly, more convenient, and involves an easier bowel prep, yet is just as effective (as optical colonoscopy) for detecting important polyps and cancers."