Early Preclinical Experience with a Novel Endobronchial Radiofrequency Ablation System for Lung Cancer Treatment

This paper introduces a novel technology for treating early-stage non-small cell lung cancer using an endobronchial approach via a flexible radiofrequency ablation (RFA) catheter. Methods - The RFA system consisted of an ablation catheter, radiofrequency generator, irrigation pump for infusion of hypertonic saline (HS) and a laptop. The catheter carried an occlusion balloon, a 5 mm long RF electrode, with irrigation holes, and a 1 mm long electrode for bipolar impedance measurements. The outer diameter was 1.4 mm for compatibility with current bronchoscopes, navigation systems and radial EBUS. The RFA system was extensively bench tested on fresh heart, liver and lung animal tissues using power levels of 30 - 60 W, RF energy delivery durations of 3 - 15 min and HS concentrations of 5% and 23.4%. Two swine were then treated at 60 W for 15 min per bronchus. Several bronchi were involved. For both animals and for all treatment sites, 20% HS was used. Animals were survived for six weeks. Results - Bench studies showed that 60 W, 7 - 15 min ablations can produce large ablation volumes, in excess of 3 - 4 cm diameter. In the chronic animal study, no clinically adverse events occurred. There was no evidence of hemorrhage. Animals vital signs, breathing patterns and their behavior were normal throughout the six-week period. Their appetite was normal and they gained weight according to expectations. The RF ablation created discrete volumes of thermal coagulative necrosis which were subsequently encapsulated ("walled off") by zones of organized fibrosis. The dimensions of coagulative necrotic sequestra met expectations, as at six weeks they exceeded volumes corresponding to 2 cm nodules, the size of tumors normally addressed in the peripheral lung by localized therapy. Conclusion - This therapy showed promise. Appropriate energy settings combined with suitable treatment locations safely produced large ablation volumes of uniform thermal coagulative necrosis. Further studies and optimization of treatment parameters can develop it into a mainstream therapy for treating early-stage lung tumors in humans.