Trial Compares Accuracy For Virtual Colonoscopy, Standard Colonoscopy
Computerized tomographic (CT) colonography, also known as virtual colonoscopy, is comparable to standard colonoscopy, which uses a long, flexible tube with a camera to view the lining of the colon, in its ability to accurately detect cancer and precancerous polyps and could serve as an initial screening exam for colorectal cancer, according to the results of the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial.
CT colonography employs virtual reality technology to produce a three-dimensional visualization that permits a thorough and minimally invasive evaluation of the entire colon and rectum. The ACRIN trial, sponsored by the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), enrolled more than 2,600 patients at 15 sites nationwide. It is the largest multi-center study to compare the accuracy of state-of-the-art CT colonography to the gold standard of conventional colonoscopy.
"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 ACRIN National CT Colonography Trial principal investigator C. Daniel Johnson, M.D., of the Mayo Clinic in Scottsdale, Ariz.
Colorectal cancer is the third most frequently diagnosed cancer and second leading cause of cancer death in men and women in the United States. Although screening recommendations vary somewhat, many recommend that adults aged 50 and older in the general population receive a colonoscopy every 10 years or more frequently, depending on known risk factors. Yet, despite the known benefits of screening, studies indicate that the majority of Americans age 50 and older are not being screened for the disease.
"Imaging advances such as virtual colonoscopy are an important step forward that could potentially increase the number of people who would agree to be screened. We hope, through continued imaging research and the development of molecular diagnostic techniques, that we will continue to improve our screening options in the years ahead and, as a result, continue to see a decline in the incidence of colorectal cancer," said NCI Director John E. Niederhuber, M.D.
"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., trial statistician, ACRIN Biostatistics and Data Management Center, Brown University, Providence, R.I.
In the ACRIN trial, the CT colonography findings were evaluated using standard colonoscopy as the reference standard. CT colonography was found to be highly accurate for the detection of intermediate and large polyps. Ninety percent of the polyps 1 centimeter or larger were detected by CT colonography. Even polyps as small as one half centimeter were detected by CT colonography with a high degree of accuracy. Since most colon cancers develop from polyps, and screening to find and remove these polyps can prevent colon cancer, an opportunity exists to save lives with early detection.
"There are clearly clinical settings in which CT colonography, colonoscopy, or both tests in combination offer distinct advantages. The most important advice we can give to patients is to get screened. How they get screened should be an individual decision based upon discussions between patients and their providers," said gastroenterologist and study author Paul Limburg, M.D., Mayo Clinic in Rochester, Minn.
Study participants had to be at least 50 years old, scheduled for a screening colonoscopy, and not have received a colonoscopy in the past five years. Each participant had a CT colonography followed by a colonoscopy, with 99 percent of both exams accomplished on the same day. Participants scheduled for a screening colonoscopy were recruited with assistance from gastroenterologists at each participating site. Preparation for CT colonography and colonoscopy both involve taking solutions to clear and cleanse the colon.
Research advocates played an important role in advising the scientists who conducted this study. "As the ACRIN patient advocate who worked with the research team and as a research advocate with C3: Colorectal Cancer Coalition, I am pleased that CT colonography can be added to the list of screening options. 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," said Pam McAllister, Madison, Wis.