Flat lesions seem to present earlier and develop more aggressively, Dr. DeVault noted, and the new technologies have helped him find such lesions.
In a randomized, multicenter study of 660 average-risk patients aged 50 years or older undergoing first-time screening colonoscopy, Dr. Kahi and his associates detected at least one adenoma in 55.5% of 321 patients using chromocolonoscopy and in 48.4% of 339 patients using white light colonoscopy. The 7.1 percentage point increase in the detection rate did not reach statistical significance, he reported.
Chromocolonoscopy detected an average of 1.3 adenomas per patient, and white light colonoscopy detected an average of 1.1 adenomas per patient, a difference that again was not significant.
There was a modest and significant increase in detection of small (less than 5 mm) or flat adenomas and detection of non-neoplastic lesions using chromocolonoscopy. High-definition chromocolonoscopy detected an average of 0.6 flat adenomas per patient, 0.8 small adenomas per patient, and 1.8 non-neoplastic lesions per patient, compared with 0.4 flat adenomas, 0.7 small adenomas, and 1.0 non-neoplastic lesions per patient with high-definition white light colonoscopy.
The two techniques did not differ significantly in detection of advanced adenomas or detection of advanced adenomas smaller than 10 mm in size.
Overall, the findings do not support routine use of high-definition chromocolonoscopy for colorectal cancer screening in average-risk patients, Dr. Kahi said.
In general, flat and depressed colon neoplasms are easy to miss on colonoscopy, he noted, but awareness is increasing that they are precursors for colorectal cancer. Flat or depressed lesions are more difficult to visualize than polypoid lesions with conventional colonoscopy and are more likely to contain high-grade dysplasia or invasive carcinoma.
Looking Back to the Future
The panelists agreed that one of the new technologies that could improve detection of larger lesions is the Third Eye Retroscope, which helps colonoscopists see lesions hidden behind folds.
Preliminary data from two studies presented at the meeting suggest that the Third Eye Retroscope may improve polyp detection during colonoscopy by 15%-20%. The Third Eye Retroscope is a disposable device inserted through the instrument channel of a conventional colonoscope after intubation to the cecum. The tip of the Retroscope bends 180 degrees so that the camera and an integrated light source can be directed back toward the tip of the colonoscope.
During the withdrawal phase of colonoscopy, a split-screen display provides both a conventional camera view and a continuous retrograde view from the Retroscope camera. The device can help find lesions located on the proximal aspect of flexures or haustral folds, panelist Dr. Daniel C. DeMarco said.
In a nonrandomized, subjective study of 340 colonoscopies, 17 endoscopists estimated that use of the Third Eye Retroscope increased detection of adenomas by 16%, reported Dr. DeMarco of Baylor University Medical Center, Dallas.
“We're finding lesions between 6 and 10 mm,” he noted. “Polyps that size that are adenomas are clinically significant.”
Of the 209 polyps found, the researchers estimated that 182 could have been detected with a conventional colonoscope, and the Third Eye yielded an additional 27—a 15% increase. Of the 116 adenomas found, an estimated 100 would have been seen by conventional colonoscopy and 16 (16%) only by the Third Eye, Dr. DeMarco said.
In a poster, A.M. Leufkens, Ph.D., and associates reported preliminary data from an ongoing prospective study that randomizes patients to get two exams by the same colonoscopist during tne period of sedation—either a standard colonoscopy followed by one with the Third Eye, or an exam with the Third Eye first, followed by regular colonoscopy.
Data on 126 of a planned 410 subjects show that endoscopists missed 2.6 times more polyps using the colonoscope alone than they did with the Third Eye as an adjunct to the colonoscope, reported Dr. Leufkens of University Medical Center, Utrecht, the Netherlands.
In 63 patients who had regular colonoscopy first, 55 polyps were found on the first exam; the second exam with the Third Eye yielded 18 more polyps for an “additional detection rate” of 32.7%. In 63 patients who were examined first with the Third Eye, 56 polyps were found initially; the second exam by colonoscopy alone yielded 7 more polyps for an additional detection rate of 12.5%.
Comoderator Dr. Samuel A. Giday of Johns Hopkins Bayview Medical Center, Baltimore, commented that “it's important that the differences we're seeing are small between the Third Eye, chromocolonoscopy, and narrow-band imaging.” More data are needed, he cautioned.
Guidelines from the American College of Gastroenterology and the American Society of Gastrointestinal Endoscopy state that high-quality screening colonoscopies are the result of four factors: an experienced colonoscopist, excellent bowel preparation, slow scope withdrawal time, and monitoring how often adenomas are being detected in screening colonoscopies, he said.