Sep. 21, 2008 More patients stand to benefit from a comprehensive, less invasive method to accurately detect colorectal cancer and precancerous polyps, a multicenter study involving Brown University and institutions nationwide has found.
The method, called computerized tomographic (CT) colonography, employs virtual reality technology to produce two- or three-dimensional visualizations that permit a thorough and minimally invasive evaluation of the entire colon and rectum. The procedure 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 problems and could serve as an initial screening exam for colorectal cancer.
The results of the American College of Radiology Imaging Network (ACRIN) National CT Colonography Trial are published in this week's issue of the New England Journal of Medicine.
The goal of the trial was to assess the accuracy of CT colonography, also known as virtual colonoscopy, using conventional colonoscopy as the gold standard. The ACRIN trial, funded by the National Cancer Institute (NCI), enrolled more than 2,600 patients at 15 sites nationwide.
“I think this is going to be a definitive study when it comes to establishing that CT colonography has a place in the armamentarium of modalities for colorectal cancer screening,” said Constantine Gatsonis, a biostatistics professor and director of the Center for Statistical Sciences at Brown. “It says that basically from here on, the question is how to implement CT colonography in screening programs.”
The center’s faculty and staff provide methodological leadership to ACRIN, design studies, and monitor and analyze the data. The center's Meridith Blevins, Mei-Hsiu Chen, Ilana Gareen, Ben Herman, and Alicia Toledano contributed to the ACRIN trial.
“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.
“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," said Chen, who led the statistical analysis at the Brown center. “The ACRIN trial has now validated that CT colonography could serve as an initial screening exam for the population in which screening is indicated.”
In the ACRIN trial, 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 last 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.
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