A New, Massive Study Demonstrates that Virtual Colonoscopy Can Be Accurate

About 150,000 Americans will be diagnosed with some form of colorectal cancer in 2008, and an additional 49,000 people will die from colon or rectal cancer this year, making this horrible form of the disease the second most deadly cancer in the world. To detect colorectal cancer, patients must be screened. Traditionally, screening demanded an invasive and painful procedure, but now an extensive study of nearly 2,600 people has demonstrated that a painless, computer-aided exam can accurately detect colorectal cancer as much as 90 percent of the time.

Computerized tomographic (CT) colonography, which is often called virtual colonoscopy, uses virtual reality- similar to video game or movie-making technology-to produce a three-dimensional rendering of a given patient's entire colon and rectum , detecting cancerous lesions and adenomas. But until recently it was not known how statistically accurate a CT colonography was in screening asymptomatic adults for disease.

Dr. C. Daniel Johnson and more than a dozen his colleagues released the results of their recent, 15-site and 2,600 person, American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial in the September 18, 2008 issue of the New England Journal of Medicine. The study aimed to determining just how accurate CT colonography is as a screening tool.

"CT colonography could be adopted into the mainstream of clinical practice as a primary option for colorectal cancer screening. We hope that this additional, less-invasive option for cancer screening will lead more people to get screened and will ultimately result in fewer deaths from colorectal cancer," said Johnson.

The study, which focused on healthy participants 50 years old or older at 15 locations around the United States, found the CT Colonography detected large (10mm or larger in diameter) adenomas and adenocarcinomas 90 percent of the time. Smaller adenomas (6mm or larger in diameter) were correctly identified about 78 percent of the time, making CT Colonography comparable to traditional and invasive colonoscopy.

"Previous single-site studies had indicated that CT colonography held promise in screening for colorectal cancer due to its accuracy, safety, cost-effectiveness, and patient acceptability. However, validation of the technique across multiple centers and radiologists was needed to provide more evidence of the exam's viability. The ACRIN trial has now validated that CT colonography could serve as an initial screening exam for the population in which screening is indicated," said Mei-Hsiu Chen, Ph.D., who served as the study's statistician.

So What is CT Colonography?

CT Colonography relies on x-rays, databases, and computer modeling to generate two- and three-dimensional images of a patient's colon or rectum, helping doctors detect colorectal polyps, diverticulosis, and cancer. You can see a video of a virtual colonoscopy online at http://www.cc.nih.gov/drd/colonoscopy.html. During a typical colonoscopy, a patient will lie on a table while a thin tube is inserted into the rectum. The tube may be inflated for better imaging.

By way of comparison, a traditional colonoscopy uses a long, flexible tube to penetrate the rectum and place a very small and warm camera in the colon.

Colon and Rectal Cancer, National Cancer Institute, downloaded on September 20, 2008 from http://www.cancer.gov/cancertopics/types/colon-and-rectal

Large, Multi-Center Trial Demonstrates Comparable Accuracy for Virtual Colonoscopy and Standard Colonoscopy, National Cancer Institute, September 17, 2008, downloaded on September 20, 2008 from http://www.cancer.gov/newscenter/pressreleases/VirtualColonoscopyRelease

Accuracy of CT Colonography for Detection of Large Adenomas and Cancers: Abstract, New England Journal of Medicine, September 18, 2008, downloaded on September 20, 2008 from http://content.nejm.org/cgi/content/short/359/12/1207

Large, Multi-Center Trial Demonstrates Comparable Accuracy for Virtual Colonoscopy and Standard Colonoscopy, National Cancer Institute, September 17, 2008, downloaded on September 20, 2008 from http://www.cancer.gov/newscenter/pressreleases/VirtualColonoscopyRelease

Accuracy of CT Colonography for Detection of Large Adenomas and Cancers: Abstract, New England Journal of Medicine, September 18, 2008, downloaded on September 20, 2008 from http://content.nejm.org/cgi/content/short/359/12/1207

Large, Multi-Center Trial Demonstrates Comparable Accuracy for Virtual Colonoscopy and Standard Colonoscopy, National Cancer Institute, September 17, 2008, downloaded on September 20, 2008 from http://www.cancer.gov/newscenter/pressreleases/VirtualColonoscopyRelease

Cancer Imaging Program, National Cancer Institute, downloaded on September 20, 2008 from http://imaging.cancer.gov/imaginginformation/cancerimaging/page9