To assess the rates of CRC at EMR scar sites of HGD lesions during surveillance colonoscopy (SC).

A multicentre cohort study analysing prospectively collected data from six tertiary referral centres was conducted. Patients with adenomatous LNPCPs resected by EMR, eligible for a minimum of 5 years of follow up, and demonstrating high-grade dysplasia (HGD) on histopathology were included. Exclusions were malignant lesions at index, serrated lesions, incomplete resections and ileocecal valve lesions due to fundamental differences in resection technique. SC was proposed at 6 months (SC1), 18 months (SC2), 3 years (SC3), and 5 years(SC4).

Over a 12-year period to December 2020, 3381 LNPCPs underwent attempted EMR, of which 494 (14.6%) with HGD met inclusion criteria. Mean age was 68, 272 were male, and median lesion size was 40mm (interquartile range [IQR] 30-50mm). A nodular component (Paris0-Is, 0-IIa+Is) was seen in 322 (67.2%). Piecemeal EMR was performed in 423 (86.6%) and margin STSC in 208 (42.1%). Six deep mural injury type IV occurred (five treated with clips, one surgery), and one (0.2%) delayed perforation resulting in surgery. SC occurred in 446/471 (95%) eligible patients at SC1 (median 6 months; IQR 5–8), 336/418 (80%) at SC2 (19 months; IQR 16–24), 203/309 (66%) at SC3 (41 months; IQR 32–51), and 107/192 (56%) at SC4 (70 months; IQR 58–83). One patient (0.2%) developed adenocarcinoma at the EMR scar (caecal lesion) at 24 months, managed with hemicolectomy (T2N0M0). 

: EMR for HGD lesions is safe and effective, with extremely low long-term CRC risk when paired with timely surveillance.