Abstract No. 617 Nonthermal ablation of pancreatic cancer in a pig model, using vascular-targeted photodynamic therapy (VTP)

Abstract

To examine whether pancreatic cancer in a pig model can be safely ablated using vascular-targeted photodynamic therapy (VTP), a nonthermal ablation modality that combines an intravascular photosensitizer (WST11) and percutaneous laser fibers. Pancreatic tumors (n=8) were induced in 5 Oncopigs (transgenic swine with Cre-inducible p53 and Kras mutations) using an adenoviral vector carrying the Cre recombinase gene. Non-thermal ablation of the tumors was performed using VTP: Intravenous infusion of WST11 (4 mg/kg, 10 min) was followed by near-infrared illumination (753 nm, 20 min) of the tumor through three optical fibers with 1-cm spacing, placed percutaneously into the tumor under CT guidance. Contrast-enhanced CT was performed immediately after, and at 7-days post ablation. Ablation sizes on CT were compared using a t test. Necropsy was performed 7 days post-ablation and lesions were examined histologically. There were no complications after ablation of pancreatic tumors (4 pancreatic head tumors, and 4 pancreatic tail tumors), based on imaging, laboratory results, and clinical evaluation. The average diameters of the ablation zones on contrast-enhanced CT increased from 1.2±0.1 cm at 200 mW/cm to 2.1±0.2 cm at 300 mW/cm (p<0.01). Pathology showed a zone of coagulative necrosis, hemorrhage, and occluded blood vessels. All vessels outside the ablation zone remained patent. VTP can be safely applied for reproducıble ablation of pancreatic tumors, while sparing large blood vessels outside the ablation zone. Preservation of nearby blood vessels could potentially enable ablation of unresectable pancreatic cancer with vascular involvement.