'Virtual Colonoscopy' Good At Detecting Colorectal Polyps



Computed tomographic (CT) colonography, also known as virtual colonoscopy, has been shown to have high accuracy in detecting cancer and precancerous polyps and could serve as a primary screening option for colorectal cancer, according to the results of a major national CT colonography trial.

The American College of Radiology Imaging Network (ACRIN) trial, sponsored by the National Cancer Institute, was conducted at UCLA and 14 other sites. It is the largest multicenter study to estimate the accuracy of state-of-the-art CT colonography. UCLA enrolled more than 150 participants in the study, with more than 2,600 volunteers participating nationwide.

In the trial, CT colonography findings were evaluated using conventional colonoscopy as the reference standard.

"CT colonography could be adopted into the mainstream of clinical practice as a primary option for colorectal cancer screening," said the trial's principal investigator, Dr. C. Daniel Johnson, of the Mayo Clinic in Scottsdale, Ariz.

Peter Zimmerman, UCLA professor of radiology and principal investigator for the UCLA arm of the study, called CT colonography a "very accurate" screening tool.

"It is our hope that this less-invasive option for screening will lead more people to get screened for colorectal cancer, which would result in fewer deaths," Zimmerman said.

CT colonography employs cutting-edge, virtual reality technology to produce three-dimensional images that are viewed as a video of the inside of the colon and permit a thorough and minimally invasive evaluation of the colorectal structure.

Colorectal cancer is the third most frequently diagnosed cancer and the second leading cause of cancer death in men and women in the U.S. Although screening recommendations vary, many physicians recommend that adults age 50 and older receive a colonoscopy every 10 years. Yet despite the known benefits of screening, studies indicate that the majority of Americans in this age group are not being screened for the disease.

"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," said trial statistician Mei-Hsiu Chen, of the ACRIN Biostatistics Center at Brown University. "However, validation of the technique across multiple centers and radiologists was needed to provide more insight about the exam's viability. The ACRIN trial has now validated that CT colonography could serve as a screening exam for the population in which screening is indicated."

CT colonography was found to be highly accurate for the detection of intermediate and large polyps. Ninety percent of polyps 1 centimeter or larger were detected using this method. Even polyps as small as a half-centimeter were detected by CT colonography with a high sensitivity. Since most colon cancers develop from polyps, and screenings to find and remove these polyps can prevent colon cancer, lives can be saved with early detection.

Study participants had to be at least 50 years old, had to be scheduled for a screening colonoscopy and could not have received a colonoscopy in the past five years. Each participant had a CT colonography, followed by a same-day colonoscopy. Participants scheduled for a screening colonoscopy were recruited with assistance from gastroenterologists at participating sites. Preparations for both CT colonography and colonoscopy involve taking solutions to cleanse the colon.

"I am pleased that CT colonography can be added to the list of screening options," said Pam McAllister, an ACRIN patient advocate and a research advocate with C3: Colorectal Cancer Coalition. "Having a method that is accurate and comprehensive while being minimally invasive is needed if we are to succeed in substantially reducing deaths from colorectal cancers."


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