EUS-guided radiofrequency ablation in the pancreas: Preliminary results in a porcine model

Background: Percutaneous radiofrequency ablation has been used to treat primary hepatocellular carcinoma and hepatic metastases lesions. This minimally invasive technique produces focal, predictable foci of coagulation necrosis with precise anatomic localization. We hypothesize that this technique may be potentially valuable for the ablation of malignant and premalignant pancreatic neoplasm such as cystic and neuroendocrine tumors. This pilot study was designed to assess the feasibility of inducing focal pancreatic ablation using EUS and a specially modified needle system. Methods: Examinations were performed in anesthetized Yorkshire pigs (50-70 kg). The pancreas was localized via EUS (Pentax 36-UX) and a modified needle (Villman 19 ga) FNA advanced into the parenchyma via a transgastric approach. Radiofrequency current (200-300 mm) was then delivered for 6 minutes at 70-90 Celsius (electrode temp). Abdominal CT scans were obtained at baseline and immediately following ablation. Pigs were then sacrificed and pathologic examination performed. One pig was observed for 24 hrs prior to sacrifice. Results: 8 pancreatic lesions were produced in 5 pigs. Lesions were evident endosonographically as round hyperechoic foci which gradually appeared surrounding the needle. CT scan demonstrated 0.8-1.2 cm focal lesions which did not enhance with intravenous contrast. Pathologic examination in those immediately sacrificed showed discrete spherical foci of coagulation necrosis measuring 8-10 mm in diameter surrounded by a 1-2 mm rim of hemorrhage. In addition, there was mild to minimal hemorrhage seen between lobuli within 1.5 cm of the needle track. In the pig followed for 24 hr, there was a 10 mm region of coagulation necrosis with no gross evidence of pancreatitis. Complications included pharyngeal perforation in one pig (related to difficult esophageal intubation) and one gastric mural burn due to incomplete penetration of the serosa prior to ablation. Conclusions: These preliminary studies demonstrate that EUS can be used to reliably deliver and thereby produce predictable foci of coagulation within the pancreas. We are presently investigating: the intermediate-term effects of this therapy including the risk of pancreatitis on a group of survival pigs.