Careful timing of illumination is important for efficient and safe photodynamic therapy of the rat esophagus

Barrett's esophagus is a premalignant lesion of the espophagus with a 30-40x greater risk of developing adenocarcinoma. Photodynamic therapy (PDT) focuses on the destruction of the Barrett's epithelium, followed by squamous re-epithelialization. Administration of S-aminolevalinic acid (ALA) induces endogenous production of the phitosensitizing agent Protoporhyrin IX (PpIX). to find optimal treatment parameters, the best time of illumination after administration of ALA and the occurrence of side-effects were determined.
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Conclusions: In the normal rat esophagus illumination at 2 h after ALA administration causes diffuse epithelial damage. Illumintaion after4, 6 or 12 h after ALA administration causes esophageal dilatation, eventually leading to functional impairment and weight loss.