Surgical margin-negative endoscopic mucosal resection with simple three-clipping technique: a randomized prospective study (with video)

Although endoscopic mucosal resection is an established colorectal polyp treatment, local recurrence occurs in 13 % of cases due to inadequate snaring. We evaluated whether pre-clipping to the muscularis propria resulted in resected specimens with negative surgical margins without thermal denaturation. Of 245 polyps from 114 patients with colorectal polyps under 20 mm, we included 188 polyps from 81 patients. We randomly allocated polyps to the conventional injection group (CG) (97 polyps) or the pre-clipping injection group (PG) (91 polyps). The PG received three-point pre-clipping to ensure ample gripping to the muscle layer on the oral and both sides of the tumor with 4 mL local injection. Endoscopic ultrasonography was performed to measure the resulting bulge. Outcomes included the number of instances of thermal denaturation of the horizontal/vertical margin (HMX/VMX) or positive horizontal/vertical margins (HM+/VM+), the shortest distance from tumor margins to resected edges, and the maximum bulge distances from tumor surface to the muscularis propria. The numbers of HMX and HM+ in the CG and PG were 27 and 6, and 9 and 2 (P = 0.001), and VMX and VM+ were 8 and 5, and 0 and 0 (P = 0.057). The shortest distance from tumor margin to resected edge [median (range), mm] in polyps in the CG and PG was 0.6 (0-2.7) and 4.7 (2.1-8.9) (P = 0.018). The maximum bulge distances were 4.6 (3.0-8.0) and 11.0 (6.8-17.0) (P = 0.005). Pre-clipping enabled surgical margin-negative resection without thermal denaturation.