Usefulness of narrow-band imaging for the detection of remnant sessile-serrated adenoma (SSA) tissue after endoscopic resection: the KASID multicenter study

Background: A sessile-serrated adenoma (SSA) has a high risk for incomplete resection. Little is known regarding how to immediately detect remnant SSA tissue after endoscopic resection. We investigated the usefulness of narrow-band imaging (NBI) to detect remnant SSA tissue after endoscopic mucosal resection (EMR). Methods: We performed a prospective randomized study on 138 patients who had suspicious SSA on colonoscopy at five centers. After EMR on the suspected SSA determined on the endoscopic morphology, all lesions were randomized into two inspection methods, NBI and white light endoscopy (WLE), to detect remnant tissue on the resected margin. If remnant tissue was detected, an additional resection was performed. Finally, we obtained quadrant biopsies on the resection margin to evaluate the incomplete resection. The proportion of incomplete resection was calculated by combining the detection of remnant tissue and the positivity of SSA cells on the final quadrant biopsies. The primary outcome was the proportion of remnant tissue detection, and the secondary outcome was the proportion of incomplete resection of SSA. Results: In all, 145 lesions from 138 patients were removed. The diagnostic rate of SSA was 87.6% (127/145). After randomization, NBI inspection was performed on 69 lesions, and WLE inspection was performed on 76 lesions. The histologic diagnostic rate of SSA was 89.9% (62/69) in the NBI group and 85.5% (65/76) in the WLE group (p > 0.05). There were no significant differences in the detection of remnant tissue (12.9% (8/62) vs. 15.4% (10/65), p > 0.05), the proportion of SSA in remnant tissue (11.3% (7/62) vs. 12.3% (8/65), p > 0.05), or the proportion of incomplete resection (6.5 (4/62) vs. 10.8 (7/65), p > 0.05) between the NBI and WLE inspection groups, respectively. Conclusion: NBI was not superior to WLE for detecting remnant SSA tissue after EMR and could not decrease the proportion of incomplete resection of SSA.