Aims Endoscopic mucosal resection (EMR) is the mainstay of therapy for large colorectal
polyps. A previous study from our group has shown low adverse events and low recurrence
rates after EMR with margin and selective base ablation using hybrid argon plasma
coagulation (hAPC) [1]. We were interested in evaluating, in a second study phase, the safety and efficacy
of EMR with systematic margin, complete base and vessel ablation using hAPC in a multicenter
prospective setting and to evaluate combined outcomes over these two study phases.
Methods Adults (18–89 years) undergoing EMR of nonpedunculated colorectal polyps≥20mm were
enrolled consecutively in a prospective multicenter study from 2019 to 2024 in Canada
(University of Montreal, University of Toronto, University of British Columbia) and
the United States (Penn State College of Medicine). In the first study phase, patients
received margin ablation using hybrid argon plasma (hAPC) after EMR, with additional
therapies at the discretion of the endoscopist including selective base ablation,
defect clipping and/or prophylactic treatment of visible vessels. In the second study
phase, patients received, after EMR completion, systematic ablation of the post-resection
margin, the complete base and any visible vessels using hAPC, with vessel ablation
as the primary prophylactic therapy for bleeding. The co-primary outcomes were adverse
events within 30 days, including severe post-endoscopic bleeding, and the proportion
of local recurrence at the first surveillance colonoscopy (SC1), based on image-enhanced
endoscopy and biopsies of the scar and based on histology of resected visible recurrences.
Results A total of 239 patients (mean age 66.5 years, 46.4% female) were included and underwent
269 EMRs (mean polyp size 34.4 mm, 78.4% proximal to the splenic flexure, 96.3% piecemeal
resections). Epinephrine was injected and/or used in the hAPC solution in 98.9%. Margin
ablation was performed in all cases, and partial or complete base ablation was performed
in 229 cases (85.1%). Prophylactic therapy of visible vessels was performed in 141
cases (52.4%) using hAPC ablation of visible vessels for the majority (108/141, 76.6%).
Defect clipping was performed in 56 cases (20.8%). Severe post-endoscopic bleeding
occurred in 2.2% [95% CI, 0.8-4.8] (6/269). Non-severe post-endoscopic bleeding occurred
in 4.5% [95% CI, 2.3-7.7] (12/269). Post-procedural perforation occurred in 0.7% [95%
CI, 0.1-2.7] (2/269). At SC1, performed at a median of 5.8 months, the overall local
recurrence rate was 2.2% [95% CI, 0.8-4.8] (6/269).
Conclusions In a prospective multicenter study, EMR with selective or complete hAPC ablation
of the resection base and visible vessels in addition to margin ablation demonstrated
high technical success, low adverse events and low recurrences. A randomized controlled
trial is ongoing to compare the safety and efficacy of base and margin ablation to
margin ablation only.
