Laser ablation of the biliary tree: in vivo proof of concept as potential treatment of unresectable cholangiocarcinoma

Objectives: The palliative treatment of cholangiocarcinoma is based on stent placement with well- known procedure-related complications. Consequently, alternative energy-based techniques were put forward with controversial long-term results. This study aims to evaluate the safety and effectiveness of biliary tree laser ablation (LA) in terms of: (i) absence of perforation, (ii) temperature increase, (iii) induced thermal damage in in vivo models. Materials and methods: The common bile duct and cystic ducts of two pigs were ablated with a diode laser (circumferential irradiation pattern) for 6 and 3 min at 7 W. Laser settings were chosen from previous ex vivo experiments. Local temperature was monitored through a fibre Bragg grating (FBG) sensor embedded into the laser delivery probe. Histopathological analysis of the ablated specimen was performed through in situ endomicroscopy, haematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide (NADH) stains. Results: Temperature reached a plateau of 53C with consequent thermal damage on the application area, regardless of laser settings and application sites. No perforation was detected macroscopically or microscopically. At the H&E stain, wall integrity was always preserved. The NADH stain allowed to evaluate damage extension. It turned out that the ablation spreading width depended on application time and duct diameter. In situ endomicroscopy revealed a clear distinction between ablated and non- ablated areas. Conclusions: The temperature distribution obtained through LA proved to induce a safe and effective intraductal coagulative necrosis of biliary ducts. These results represent the basis for further experi- ments on tumour-bearing models for the treatment of obstructive cholangiocarcinoma.