Sensitization and photodynamic therapy of normal pancreas,duodenum and bile ducts in the hamster using 5-aminolaevulinic acid

Photodynamic therapy (PDT) using 5-aminolaevulinic-acid-(ALA)-induced protoporphyrin IX (PPIX) increases survival in hamsters with pancreatic cancer. However, experiments with other photosensitizers on this model show a high risk of duodenal perforation. In this paper, the pharmacokinetics and PDT effects of ALA on normal tissues in the pancreatobiliary region are presented. Using quantitative fluorescence microscopy, maximum PPIX fluorescence was seen in the bile ducts, less in the duodenal mucosa and least in the muscularis propria and pancreas. For PDT, 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 damage without perforation. Surface irradiation of the whole periampullary region (50 J cm^–2) caused extensive damage, sometimes with perforation. 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.