SAN DIEGO — Colonoscopy remains the standard for imaging the colon, but the future may rest in nonoptical techniques such as virtual colonography and colonic visualization devices such as the PillCam, Dr. P. Jay Pasricha said at a meeting jointly sponsored by the AGA Institute and the Japanese Society of Gastroenterology.
“For a long time, colonoscopy was considered a done deal in terms of technology,” said Dr. Pasricha, chief of the division of gastroenterology and hepatology at the University of Texas, Galveston. “But it's interesting to see in the last 3-4 years that there has been a virtual revolution in the way we're thinking about colonoscopy.”
One force that has led to innovations is patients themselves, who are increasingly concerned about safety and “hassle” factors such as inconveniences related to sedation.
“They also want standardization of quality,” Dr. Pasricha said. “They don't want to go to one endoscopist and have one outcome and go to another endoscopist and have another outcome. They think of this as a standardized test; they don't view colonoscopy as a variable. It should be done the same way with the same results every time. The patients expect that.”
Another force driving new technologies is physicians who are concerned about the limitations of colonoscopy. The “miss rate” of conventional colonoscopy for adenomas greater than 1 cm is 12%-17%, Dr. Pasricha said. Reasons why adenomas are missed include anatomical factors, such as lesions hiding behind folds, and variability in examiner skills. Detection rates can vary 4- to 10-fold among clinicians in the same practice, he noted.
“Some of it is skill, some of it is the interpretation, and some of it is just how long you take,” he said. “The pressure of time has become very important in today's practice. Longer withdrawal times improve detection rates.”
He added that colonoscopy as it is currently practiced—as opposed to the large national trials, such as the National Polyp Study—“may not consistently protect against colorectal cancer or prevent mortality. However, this is the implicit promise that we have offered to our patients. Are we really delivering on that promise? We need to be sure.”
Last year, a joint task force of the American College of Gastroenterology and the American Society for Gastrointestinal Endoscopy recommended that the withdrawal time for examining the mucosa should be at least 6 minutes. As a measure of efficacy, clinicians should be able to document that 25% of male patients and 15% of female patients older than age 50 years had one or more adenomas.
Even if you follow the best-practice guidelines, clinicians “still have this problem of excessive demand [for colonoscopies] and the pressure to do more,” Dr. Pasricha said.
“You are going to have to spend more time per colonoscopy if you adhere to these guidelines. You're going to get less well paid for the time you spend if current trends in reimbursement continue; there are going to be increases in liability and probably increases in patient dissatisfaction as our performance, in terms of missed rates, gets publicity. That's going to lead to increasing oversight by regulatory agencies,” Dr. Pasricha said.
The good news, he noted, is that almost all of these problems are amenable to technologic solutions. One solution is to use nonoptical techniques such as virtual colonography and improved biomarkers.
Virtual colonography is a high-resolution CT scan with a software program that allows you to recreate or simulate the colon. “Some researchers have suggested that the sensitivity is not as good, but there are a lot of new developments in this area that are probably going to make this a reality,” he said. “It's going to be along the lines of computer-aided diagnosis, which is really going to shorten the time frame for interpretation of images.”
“Prepless” CT colonography, which eliminates the need to cleanse the colon, is another promising approach. “Once that becomes a reality, probably in the next 2-3 years, you will see a lot of patients embrace this,” he said.
Combining CT colonography with colonoscopy also shows promise. One study suggests that if you stratify patients into low-risk and high-risk categories, with the former undergoing colonoscopy directly while the latter undergo CT colonography as the initial test, you can detect 89% of advanced neoplasia, with far fewer colonoscopies being performed, compared with a rate of 94% when universal colonoscopy was performed (Gastroenterology 2006;131:1011-9).
Other promising alternatives to colonoscopy include non-physician-based colonic visualization devices such as the Aer-O-Scope and the PillCam. The Aer-O-Scope, an investigational device made by G.I. View Ltd., is a disposable, self-propelling visualization device that travels from the rectum to the cecum. It has two balloons: The distal balloon contains an optical scanning component, whereas the proximal balloon seals off the rectum.