Gastric neoplasms (GNs) occur in approximately 10–30% of patients with familial adenomatous polyposis (FAP). While several recent studies have demonstrated the benefits of intensive endoscopic interventions for colorectal and duodenal lesions in FAP [1,2], evidence regarding such strategies for GNs remains scarce. Moreover, there are no established guidelines for endoscopic management of FAP-associated GNs, and the most appropriate resection method has yet to be defined. Recently, gel immersion endoscopic mucosal resection (GI-EMR) using Viscoclear (Otsuka Pharmaceutical Factory, Tokushima, Japan), an endoscopic field-of-view securing gel, has been reported [3]. This method provides a clear field of view even in the presence of residue or mucus, allowing for accurate resection under direct visualization while maintaining the simplicity of underwater EMR (UEMR). A previous report demonstrated that GI-EMR in the duodenum reduced procedure time and increased R0 resection rates compared with UEMR [4], suggesting potential advantages for gastric lesions as well. A previous report suggested the effectiveness of GI-EMR for GNs in patients with FAP [5], indicating its potential as an endoscopic therapeutic intervention for such lesions. However, no previous studies have evaluated treatment outcomes of GI-EMR for GNs in patients with FAP. This study aimed to evaluate the effectiveness of GI-EMR for GNs in patients with FAP compared with conventional resection methods.

This was a multicenter, retrospective, observational study of patients with FAP who underwent endoscopic resection for GNs between April 2011 and November 2024. Currently, there is no established consensus on the optimal resection method for FAP-associated GNs. In this study, ESD, which has been mainly performed for sporadic GNs (even those measuring ≤20 mm), was tentatively adopted as the standard treatment for FAP-associated GNs. Using this provisional standard as a basis, we conducted a comparative analysis with the newly developed GI-EMR technique. To compare treatment outcomes between GI-EMR and ESD, we identified cases of GNs measuring ≤20 mm in diameter, with protruding or flat elevated morphologies, which were indications for GI-EMR at our institutions, from patients who underwent endoscopic resection during the study period. In the GI-EMR procedure, the gel was injected into the stomach through the accessory channel using a syringe and the BioShield irrigator (U.S. Endoscopy). The lesion was then carefully captured with a snare and resected using a blended cut current setting (Endocut Q; effect 3, time interval 2, time duration 2).

A total of 27 GNs (seven patients) ≤20 mm in size with flat elevated or protruding morphology, in which ESD or GI-EMR was performed, were analyzed, consisting of 15 ESD and 12 GI-EMR cases. The median lesion size did not differ significantly between groups (10 mm vs. 11.5 mm, respectively, P=0.30). En bloc resection rates were 100% in both groups, while R0 resection rates were 100% for ESD and 83.3% for GI-EMR (P=0.19). The median procedure time was significantly shorter in the GI-EMR group compared with the ESD group (2 min vs. 47 min, P<0.001). Intraoperative perforation occurred in one ESD case (6.7%), but was not observed in the GI-EMR group. No delayed bleeding or perforation was reported in either group. During a median follow-up of 22.3 months, no local recurrence was observed in either group.

GI-EMR appears to be a safe and effective treatment option for GNs in patients with FAP. Although GI-EMR may be less invasive compared to ESD, the limited number of cases warrants additional studies to substantiate its safety and effectiveness.