SAN ANTONIO – , Carol Rouphael, MD, reported at the annual meeting of the American College of Gastroenterology.
She presented a retrospective study of 3,377 patients who had their first colonoscopies at age 50 or older in 2006 or later, when high-definition colonscopes took over.
The clinical implications of the study are clear: “Our findings suggest the colonoscopy interval for individuals with three or more nonadvanced adenomas should be similar to low-risk adenoma patients; that is, 5-10 years,” said Dr. Rouphael, a gastroenterology fellow at the Cleveland Clinic.
Studies conducted in the early 2000s using standard-definition colonoscopes showed that the risk of metachronous advanced neoplasia (MAN) – that is, colorectal cancer or a pathologically advanced adenoma – was twice as great in patients with three or more small tubular adenomas compared with patients with just one or two of them. Thus, guidelines called for such patients to undergo repeat colonoscopy at a shorter time interval post polypectomy, typically 3 years. But with contemporary colonoscopy using high-definition optics, gastroenterologists are detecting a lot more small adenomas. Dr. Rouphael and coworkers wondered if the definition of high risk established more than a decade ago, prior to the use of high-definition colonoscopes, still held true. They concluded that the answer is no.
Eleven percent of patients in their study had features indicative of high-risk adenoma on the initial colonoscopy. Twenty-four percent of these patients had an adenoma with advanced pathology, meaning villous features or high-grade dysplasia; 51% had an adenoma 10 mm or more in size without advanced pathology; and the remaining 25% of patients were classified as having high-risk adenoma on the basis of having three or more small tubular adenomas.
Follow-up colonoscopy was performed a median of 42 months later in the high-risk adenoma group, 54 months later in the low-risk adenoma patients with one or two small tubular adenomas, and at 61 months in those with no adenomas. At follow-up, MAN was discovered in 3.8% of patients with no adenomas at baseline, 4.6% of the low-risk adenoma group, and 9.3% of the overall high-risk adenoma group. However, within the high-risk adenoma group the risk of MAN varied widely: 6.3% in patients with three or more nonadvanced adenomas, 6.1% in those with three or four nonadvanced adenomas, 7.7% in patients with five or more nonadvanced adenomas, 8.3% in those with a 10-mm or larger adenoma without advanced pathology, and 14.6% in patients with an adenoma with advanced pathology at baseline.
In a multivariate analysis adjusted for age, sex, ethnicity, and time between first and follow-up colonoscopy, the risk of MAN did not differ significantly between patients with three or four nonadvanced adenomas and those with one or two, nor between patients with five or more versus one or two. In addition, there was no significant difference in MAN risk between patients with no adenomas at baseline and those with one or two low-risk, nonadvanced adenomas. In contrast, patients with a 10-mm or larger adenoma without advanced pathology at baseline were 1.9-fold more likely to have MAN at follow-up colonoscopy than were patients with one or two small tubular adenomas. And patients having an adenoma with advanced pathology at baseline were at 3.7-fold greater risk of developing MAN than were those with baseline low-risk adenoma, according to Dr. Rouphael.
She reported having no financial conflicts regarding her study, which won the Fellows-in-Training Award at the annual meeting.
SOURCE: Rouphael C. ACG 2019 Abstract 9.