Serrated lesions and adenomas in colonoscopic surveillance: additive or exponential?

Our view of serrated polyps has come a long way in the last two decades, moving from seeing them as benign lesions that do not develop into cancer to recognising them as lesions that may account for up to one-third of all colorectal cancers (CRCs).1 The ‘serrated pathway’ to CRC is now widely accepted, and serrated lesions are now a target for identification and removal at screening colonoscopy. They represent a special challenge for colonoscopists as they are difficult to detect and are up to 3.7 times more likely than adenomas to be incompletely resected.2 It is assumed that removal of precursor serrated lesions prevents development of CRC in the future; however, direct evidence for this is much more limited than for adenomas. Work on intensive surveillance of patients with serrated polyposis syndrome suggests that effective detection and resection can reduce cancer risk in a polyposis scenario.3 The role of adenomas in colonoscopic screening is not just limited to being a removable precursor lesion that halts the ‘adenoma–carcinoma sequence’ to reduce future risk. Adenoma size and multiplicity also predicts future risk of developing further advanced adenomas or CRC. On this basis, international guidelines have recommended surveillance examinations after large or multiple adenomas have been resected.4 5 Data to support such an approach for serrated polyps have been much more limited, in part because we do not have large longitudinal datasets at times where serrated polyps were being effectively detected by colonoscopists, and correctly classified by pathologists. The study by Li et al in Gut is therefore a very welcome addition …