Importance of fluence rate in photodynamic therapy with ALA-induced PpIX and BPD-MA in a rat bladder tumor model

Oxygen dependent phototoxicity was investigated in vivo in an orthotopic rat bladder tumor model. Two photosensitizers, benzoporphyrin derivative monoacid ring A and 5-aminolevulinic acid-induced protoporphyrin IX were studied. For a given cumulative light dose of 30 J/cm 2, enhanced tumor destruction was obtained for both photosensitizers by either using a low fluence rate or fractionated light delivery mode. These observations may be attributed to rapid local oxygen consumption during photochemical reactions.