An investigation of photodynamic therapy in the treatment of pancreatic carcinoma: Dihematoporphyrin ether uptake and photobleaching kinetics

Results of dihematoporphyrin ether (DHE) uptake and fluorescence kinetics show that the concentration in the pancreas is on the order of 40-60 μg DHE/g of tissue at an injected dose of 40 mg/kg. Previously concentrations on this order have only been found in organs of the reticuloendothelial system. Two intrapancreatic carcinoma models, one of acinar origin (rat) and one of ductal orgin (hamster), were studied. Both showed equal or higher concentrations of DHE as compared to normal pancreas when fluorescence measurements and chemical extraction procedures were performed. Photodynamic therapy (PDT) treatment of the normal pancreas and pancreatic tumors yielded atypical results. When the normal pancreas with DHE present is exposed to 630 nm light from a dye laser (75 mW/cm², 30 min), the normal photobleaching measurable by fluorescence decay does not occur. Yet, the pancreatic tumor responds with a relatively normal fluorescence decay pattern, with hemorrhaging and a resultant loss of measurable DHE concentration. These results represent the emergence of an entirely new modality, with substantial potential for the treatment of cancer of the pancreas.