Tae Il Kim, MD, PhD, from the Department of Internal Medicine, Yonsei University College of Medicine, in Seoul, Korea discusses this Original Article “High-risk metachronous polyps are more frequent in patients with traditional serrated adenomas than in patients with conventional adenomas: a multicenter prospective study.”
Conventional adenomas (CAs) are major precursor lesions of colorectal cancer (CRC). However, the importance of serrated polyps, a heterogeneous group of lesions that include hyperplastic polyps (HPs), sessile serrated adenomas (SSAs), and traditional serrated adenomas (TSAs) with variable malignant potential, has been recognized recently because of their possible contribution to interval cancer. Although the malignant progression of serrated adenomas, especially the relationship between SSAs and interval cancer, has been underlined, the malignant potential of TSAs has not been well established. In addition, current guidelines for serrated polyps recommend a 3-year colonoscopic surveillance interval in TSA cases, but the quality of evidence supporting this recommendation is low. Therefore, to assess the relative rate of neoplastic development and progression in TSAs, we compared the risk of metachronous polyp occurrence during surveillance between TSAs and CAs after removal of the initial polyps.
Most studies suggest that serrated adenomas have significant malignant potential and are associated with increased development of metachronous polyps, synchronous advanced conventional neoplasias, and CRC compared with CAs. In addition, some authors indicate that SSAs are more likely to progress to CRC than TSAs. However, only a few small studies have compared the malignant potential between CAs and TSAs, and results have been conflicting. Because of interobserver variation in pathologic interpretation, few studies have carefully categorized serrated polyps based on histology and included a sufficient long-term follow-up. We used the prospective multicenter patient cohort, in which all polyps were reclassified into CAs, HPs, TSAs or SSAs by specialized GI pathologists, to reduce interobserver variability in the initial diagnosis.
TSAs are associated with a higher recurrence rate of all subtypes of polyps, including CAs, serrated adenomas, and HPs, compared with CAs. Furthermore, patients with TSAs on baseline colonoscopy had a greater number of and larger-sized polyps and were more likely to have high-risk metachronous polyps in surveillance colonoscopies than patients with CAs, and the presence of TSAs on an initial colonoscopy was one of the most significant factors predicting the presence of high-risk adenomas on surveillance colonoscopies.
Elaborate colonoscopy follow-ups and prospective investigation of patients with TSAs should be undertaken to identify the natural history and determine optimal surveillance.
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