Although colorectal polyps smaller than 10 mm are usually removed by cold snare polypectomy (CSP), small polyps sometimes include high-grade dysplasia or intramucosal carcinoma, which require endoscopic resection with electrocautery including hot snare polypectomy (HSP) and endoscopic mucosal resection (EMR), because they have the potential to invade the muscularis mucosa. However, endoscopic resection with electrocautery carries a non-negligible risk of adverse events, including bleeding and perforation, due to deep thermal injury. Thus, low-power pure-cut hot snare polypectomy (LPPC-HSP) has been developed as a minimally invasive technique with low power, low voltage, and no coagulation current [1,2]. This method uses pure-cut current and reduces the power of electrocautery, expecting less deep thermal damage compared with conventional HSP with blend or coagulation current, resulting in a lower risk of perforation and bleeding. To determine whether LPPC-HSP is appropriate for lesions such as high-grade dysplasia and intramucosal carcinoma that can extend into the muscularis mucosa, it is necessary to examine the actual resection depth of LPPC-HSP; however, its actual resection depth has not been evaluated. This study aimed to investigate the resection ability of LPPC-HSP for small colorectal polyps.

This single-arm, prospective, observational study included patients who underwent LPPC-HSP for nonpedunculated colorectal polyps smaller than 10 mm. For LPPC-HSP, a 10- or 15-mm oval snare with a wire diameter of 0.30 mm (SnareMaster Plus S Olympus Medical Co.) was used without submucosal injection, and the polyps were resected with a low-power pure-cut current (Autocut; VIO300D: effect, 1 [10 W]; VIO3: effect, 0.4). The primary outcome was the rate of sufficient vertical R0 resection (SVR0) [3], defined as R0 resection that included a sufficient submucosal layer beneath the whole lesion. Based on previous studies of EMR for small colorectal polyps, which reported the R0 resection rates of EMR ranging from 62% to 87.3% and the containing submucosal tissue rate of 92%, the expected rate of SVR0 was set at 70%. With a non-inferiority margin of 10%, the pre-defined threshold rate was set at 60%. The secondary outcomes were the en bloc resection rate, the incidence of adverse events, and the pathological evaluation including the R0 resection rate, the proportion of specimens containing muscularis mucosae and the submucosa, and the thickness of the submucosa.

Finally, this study included 95 patients with 150 lesions. En bloc resection was achieved in all cases. R0 resection was achieved in 124 lesions (83%). All specimens contained the muscularis mucosa, and the submucosa tissue was included in 132 lesions (88%). The median maximum submucosal layer thickness was 1331 μm (IQR, 736-2044). The primary outcome, the SVR0 rate, was 115 lesions (76.7 %; 90% confidence interval [90% CI], 70.3–82.2%). The lower limit of the 90% CI exceeded the pre-defined threshold of 60%, thereby meeting the primary endpoint. No bleeding, perforation, or other serious adverse events occurred.

The vertical resection ability of LPPC-HSP was acceptable. LPPC-HSP may be applicable to colorectal polyps smaller than 10 mm that have potential malignancy, similar to conventional resection methods with electrocautery.