Evaluation of the in vivo effect of argon plasma coagulation with prior submucosal injection (Hybrid APC) in the esophagus of pigs

Background Although argon-plasma coagulation (APC) is useful for treating early gastrointestinal cancer, safer ablation for oesophageal cancer is needed because the esophageal wall is very thin. The efficacy of APC with prior submucosal injection of saline (hybrid APC) by using a resected oesophagus of pig has been reported, but there has been no study in which the effects, biological reactions and delayed adverse effects of hybrid APC were evaluated. In this study, we evaluated the histological efficacy of APC with prior submucosal injection of saline (hybrid APC) by using an in vivo porcine model. Methods APC alone and hybrid APC were performed. Various settings of argon were used. The pigs were sacrificed after treatment (study 1) and 1 week after treatment (study 2). Histological evaluation of the deepest spot of coagulation from the basal layer (study 1) and non-atrophic muscle zone (study 2) in resected specimens was performed. Type A damage was defined as superficial tissue damage of the tunica mucosa, whereas type B damage was defined as an injury pattern limited to the tunica muscularis. The depths of type A and type B damage were measured in study 1. Immunohistochemical analysis was also performed in study 2. Results (study 1) Hybrid APC except for that at an excessive setting could prevent type B damage of the muscle layer. Standard APC at any setting could not prevent type B damage of the muscle layer. Results (study 2) The non-atrophic muscle zone was significantly larger in the hybrid APC group. Immunohistochemical analysis showed that the numbers of activated myofibroblasts and infiltrating neutrophils and macrophages were significantly smaller in the hybrid APC group than in the standard APC group. Conclusion APC following submucosal injection of saline contributes to sufficient and safe coagulation for oesophageal lesions.