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

Abstract

Background: Our aim in this study was to investigate the feasibility and safety of performing radiofrequency (RF) ablation in the pancreas with endoscopic ultrasound (EUS).

Methods: RF was applied to normal pancreatic tissue in 13 anesthetized Yorkshire pigs with specially modified 19-gauge needle electrodes (1.0 to 1.5 cm tip). The pancreas was localized with EUS and punctured through a transgastric approach. RF current (285 +/- 120 mA) was delivered for 6 minutes. Diagnostic imaging (EUS and CT) and serum amylase and lipase levels were obtained at baseline, immediately after ablation, and 1 to 14 days after the procedure. Pigs were killed immediately (n = 5), 1 to 2 days after ablation (n = 2), and 2 weeks after the procedure (n = 6). Pathologic examination was performed.

Results: Sixteen ablations were performed. During ablation, round hyperechoic foci (diameter to 1.0 cm) gradually surrounded the tip of the electrode. Immediately after the procedure CT demonstrated 1 cm hypodense foci that did not enhance with iodinated contrast. In pigs killed immediately and 1 to 2 days after ablation, pathologic examination showed discrete, well-demarcated spherical foci of coagulation necrosis measuring 8 to 12 mm in diameter surrounded by a 1 to 2 mm rim of hemorrhage. Radiologic-pathologic correlation was within 2 mm. In 4 of 6 (67%) pigs killed on day 14, retraction of the coagulated focus was observed. A 1 to 3 mm fibrotic capsule surrounded the coagulated tissue in the remaining 2 pigs. One pig had mild hyperlipasemia, a focal zone of pancreatitis (<1 cm), and later a pancreatic fluid collection. Biochemical parameters were normal in the remaining pigs. Other complications included three gastric and one intestinal burn caused by improper electrode placement.

Conclusions: EUS-guided RF ablation can be used safely to produce discrete zones of coagulation necrosis in the porcine pancreas. Potential clinical uses of this technology include management of small neuroendocrine tumors and possibly palliation of unresectable pancreatic adenocarcinoma.