An animal model of Photodynaniic Therapy induced esophageal stricture - preliminary report

摘要

Photodynamic Therapy (PDT) using Photofrin has been recently approved by the FDA for the treatment of esophageal cancer and Barrett's esophagus. A major limitation of PDT for Barrett's esophagus is the development of esophageal stricture in up to 53% of patients. Mechanisms of PDT stricture formation have not been elucidated. The major difficulty is the lack of an animal model for PDT-induced stricture. We have used a pig model in which the esophagus is very similar to that of the human esophagus. Two (Scrofa) domestic pigs were injected with Photofrin at dosage of 2 mg/kg 48 hours prior to photoactivadon with 630 nm light. Following anesthesia, a laser probe (2.5 cm in length) was passed through the oral cavity to approximately the mid-point of the esophagus via an endoscope. Light energy (400 Joules (J)/cm) was delivered as a single dose in one pig or repeated at 72 hours in the second pig. In this pig model, upper endoscopy, Barium swallow and pathological studies confirmed stricture formation following esophageal PDT exposure of 400 J as one or two fractions. We believe that this is the first animal model created to study esophageal strictures resulting from PDT.