SENSITIZATION AND PHOTODYNAMIC THERAPY OF NORMAL PANCREAS, DUODENUM AND BILE-DUCTS IN THE HAMSTER USING 5-AMINOLEVULINIC ACID

Photodynamic therapy (PDT) using 5-aminolaevulinic-acid-(ALA)-induced protoporphyrin IX (PPIX) increases survival in hamsters with pancreati c cancer. However, experiments with other photosensitizers on this mod el show a high risk of duodenal perforation. In this paper, the pharma cokinetics and PDT effects of ALA on normal tissues in the pancreatobi liary region are presented. Using quantitative fluorescence microscopy , maximum PPIX fluorescence was seen in the bile ducts, less in the du odenal mucosa and least in the muscularis propria and pancreas. For PD T, light was delivered either using a bare fibre touching the tissue ( single-point illumination), or irradiating a 1.5 cm diameter circular area. Single-point PDT (50 J) produced only localized reversible damag e without perforation, Surface irradiation of the whole periampullary region (50 J cm(-2)) caused extensive damage, sometimes with perforati on, Before PDT can be used safely to treat tumours of the pancreas and bile duct, further studies are necessary to understand its effect on larger areas of normal tissue.