Reducing Neoplasia Recurrence After Endoscopic Resection of Large Colorectal Polyps

This trial is an open-label, two-arm, parallel-group, multicenter, randomized controlled superiority trial. Patients undergoing EMR will be randomly assigned in a 1:1 ratio to undergo additional STSC margin ablation (control group and current standard of care) or h-APC ablation of the margins and base (experimental group). Patients will be enrolled in the study before the endoscopy procedure, or in the outpatient clinic. Eligible patients who have consented to participate in the study will be asked to take a standard colonoscopy preparation regimen before their scheduled procedure. EMR intervention will be performed for all eligible patients with a large laterally spreading lesions (LSLs) by expert endoscopists. Only if a polyp meets inclusion criteria, the study subject will be enrolled and randomized into one of these 2 groups: * Group 1: EMR + h-APC margin and base thermal ablation * Group 2: EMR + STSC of the margin The standard EMR technique will be used for the primary removal of all polyps. Submucosal injection will be used to lift the polyp from the muscularis propria. Injection will be used as per the current standard of care using a contrast agent and a lifting agent (e.g., NaCl 0.9% or Voluven). Snare electrocautery resection will be facilitated until complete visible removal of the complete polyp. Electrocautery snare technique will be facilitated using standard microprocessor-controlled electrocautery. If residual polyp tissue cannot be removed by a snare, other means such as cold snare (i.e., for small residual polyp tissue that cannot be engaged into standard snares) or avulsive methods will be used. Randomization will be performed after resection is complete and before thermal ablation. After the complete removal of the polyp, depending on the randomization group, h-APC or STSC techniques will be used for margin and base or only margin ablation of the post-EMR defect. If multiple large polyps are found and removed, the study polyp will be marked with two tattoos 3 cm distal and 3 cm proximal to the lesion, to clearly identify the study polyp associated scar in the follow-up colonoscopy. Polyps will be sent to the pathology lab and evaluated according to standard practice by institutional pathologists. To determine the homogeneity and depth of h-APC margin ablation in the pathology lab, some ablated margins might be resected using the standard cold snare technique. Telephone calls after 14 days following the EMR will be conducted to assess possible adverse events that occurred within the first 14 days after EMR. Follow-up 1: Surveillance colonoscopy occurring 6 months after the EMR intervention for the assessment of recurrence (biopsy from the post-EMR site to be confirmed by pathology) following the intervention (h-APC) and the control (STSC) techniques. Follow-up 2: Surveillance colonoscopy at 18 months (± 6 months) after the EMR intervention for the assessment of recurrence (biopsy from the post-EMR site to be confirmed by pathology) at FU1. Patients with visible recurrence at the EMR site will undergo additional resection for complete eradication of recurrence. Patients with no visible but pathology-confirmed recurrence will be rescheduled for another colonoscopy with subsequent treatment of the post-EMR site and another follow-up colonoscopy for biopsies and confirmation of complete/incomplete eradication within 18 months after the initial EMR.