Given the risk of colon cancer in people with long-standing ulcerative colitis (UC), the standard of care calls for regular surveillance colonoscopies. But Michael F. Picco, M.D., a gastroenterologist at Mayo Clinic in Jacksonville, Fla., argues that white-light endoscopy with random biopsy sampling is an imperfect way of detecting early signs of dysplasia.
"Lesions in patients with UC are generally flat, making them difficult to see with conventional colonoscopy," he says. "And taking dozens of random samples doesn't guarantee that we're not missing cancer somewhere in the colon."
But he says that chromoendoscopy, a relatively simple technique that stains the colon with dye, can enhance the detection of precancerous lesions.
"Chromoendoscopy allows us to target areas of the colon more efficiently, increasing the likelihood of finding dysplastic changes. In fact, previous studies have shown up to a fourfold increase in the diagnostic yield for intraepithelial neoplasias using chromoendoscopy."
Dr. Picco adds such impressive results are generally obtained when chromoendoscopy is performed by highly experienced endoscopists working in specialized centers. "For the technique to gain wider acceptance, interobserver agreement on abnormalities is essential."
To confirm the feasibility of chromoendoscopy and assess interobserver agreement, Dr. Picco led a recent study in which investigators from all three Mayo sites who were unfamiliar with chromoendoscopy analyzed more than 500 white-light and indigo carmine chromoendoscopy images obtained during surveillance colonoscopy on 57 patients with UC.
The images contained 155 polyp abnormalities. The majority of the lesions were less than 0.4 inches (1 centimeter), and included 86 pseudopolyps as well as 40 hyperplastic, 18 adenomatous and 11 dysplastic lesions.
Dr. Picco says that investigators identified between 126 and 149 of the abnormalities, leading to an overall agreement rate of 95 percent. The number of missed polyps was low and confined to very small lesions — less than 0.2 inches (5 millimeters).
"Although preliminary, these results show that chromoendoscopy can be successfully used by inexperienced observers," he says. "The technique adds about 15 minutes to the standard surveillance colonoscopy procedure, but the fourfold yield is well worth it."
He notes that the additional time is needed not just for staining the colon but also for taking standard random biopsies. "In the future, enhanced detection methods like chromoendoscopy may eliminate the need for random biopsies, saving both time and laboratory fees."
Other study investigators include:
Dr. Picco, along with Dr. Wallace, is also investigating the use of confocal microscopy for ulcerative colitis surveillance. In this study, patients first undergo chromoendoscopy. Any lesions seen are then visualized using the confocal microscope, which provides up to 1000 times magnification. The aim is to determine whether a diagnosis of dysplasia can be made on living tissue without having to perform biopsies. The study, which is ongoing, has enrolled 40 patients to date.