SAN DIEGO — Colonoscopists are finding more polyps thanks to advances in technology, but it's not yet clear that detection of these additional lesions will change patient outcomes.
The initial impact of new techniques—such as high-definition colonoscopy, narrow-band imaging, chromocolonoscopy, and adjunctive viewing with the Third Eye Retroscope—may be felt mainly as rising health care costs and increasing numbers of patients who are advised to get their next screening colonoscopy in 5 years instead of 10.
A panel of expert endoscopists at the annual meeting of the American College of Gastroenterology agreed that although there's no hard evidence on the benefit of removing polyps smaller than 6 mm, they take them out if they see them.
“We haven't shown yet that finding small 4-mm and 5-mm polyps makes a difference in preventing colon cancer,” said Dr. Walter J. Coyle of the Scripps Clinic, La Jolla, Calif., who comoderated the session. But with increased detection, “we're going to be screening these people more frequently.”
Smaller lesions predict larger ones, and the “adenoma to cancer” sequence suggests that getting any adenoma out is a good thing, Dr. Kenneth R. DeVault suggested. Although no randomized trials have shown that removing smaller lesions reduces mortality, “we believe it does, and it makes sense that it does, but it's not been unequivocally proven that finding a 3-mm adenoma changes things.”
And it may never be proven, because people are unlikely to tolerate randomization to watch-and-wait management of a 5-mm polyp, said Dr. DeVault of the Mayo Clinic, Jacksonville, Fla. However, studies of virtual colonoscopy may yield useful information on the natural history of small polyps.
High-Def Detection Rates
Dr. DeVault and his associates reported on a study showing that high-definition white light colonoscopy increased adenoma detection, compared with standard-definition white light colonoscopy.
Unexpectedly, increased detection of some adenomas using high-definition white light colonoscopy did not produce a “learning effect” leading to increased detection using standard-definition white light colonoscopy, as suggested by at least one previous study (Gut 2008;57:59-64).
In the current comparison, the adenoma detection rate for standard-definition white light colonoscopy did not increases over the course of the study and remained significantly lower than detection with high-definition equipment, Dr. Anna M. Buchner reported at the meeting.
They investigators conducted a “natural experiment” from October 2006 to March 2007 at their institution, the Mayo Clinic in Jacksonville, when the clinic wanted to upgrade to high-definition equipment but lacked the funds to replace all their colonoscopes at once, Dr. DeVault said. They randomized patients and physicians to one of three rooms with high-definition white light colonoscopes or one of three rooms with standard equipment.
High-definition white light colonoscopy used for 1,204 patients showed significantly better detection rates for all polyps (42%), hyperplastic polyps (20%), and adenomas (29%), compared with detection rates using standard-definition white light colonoscopy in 1,226 patients (38% for all polyps, 17% for hyperplastic polyps, and 24% for adenomas), reported Dr. Buchner, who is now with the University of Pennsylvania, Radnor.
Small or moderate-sized adenomas were significantly more likely to be detected by high-definition colonoscopy than with standard-definition imaging: Detection rates for adenomas sized 0-5 mm were about 21% with high-definition colonoscopy and 17% with standard-definition equipment. Detection rates for adenomas sized 6-9 mm were about 8% with high-definition colonoscopy and 6% with standard-definition technology. High-definition colonoscopy also was more likely to detect polyps on the left side of the colon, she added.
For adenomas larger than 10 mm, detection rates were similar with the two techniques. Over the course of the study, detection of polyps overall increased, but adenoma detection did not.
Detecting Polyps and Adenomas
Dr. Lianne K. Cavell and her associates reported in a poster presentation that high-definition colonoscopy significantly increased detection of all polyps, compared with standard-definition colonoscopy, but did not improve detection of adenomas.
Her study compared charts for 345 patients who underwent standard-definition colonoscopy with data on 375 patients examined after the introduction of high-resolution colonoscopy. Polyps were detected in 36% of patients with high-definition colonoscopy and 29% of patients with standard-definition colonoscopy. Adenomas were detected in 53% and 47%, respectively, but that difference was not statistically significant, said Dr. Cavell of New York–Presbyterian Hospital.
The potential downside of new imaging technology is that resection of potentially insignificant polyps may increase pathology costs, procedure times, and risks related to colonoscopy, she noted.
In a study presented by panelist Dr. Charles J. Kahi, high-definition chromocolonoscopy did not significantly increase detection of adenomas, compared with high-definition white light colonoscopy. Chromocolonoscopy did, however, significantly increase detection of flat lesions, reported Dr. Kahi of Indiana University, Bloomington.