Mechanisms contributing to optimization of PDT with first-generation photosensitizers

摘要

Improved control of tumor growth has been accomplished by modification of the irradiation scheme applied to hematoporphyrin-induced sensitization. Significantly enhanced efficacy of PDT was seen with either reduction of fluence rate or with an intermittent light-dark protocol, together suggesting that consideration must be given to photochemical oxygen depletion as a rate- limiting component in the production of singlet oxygen, the mediator of cytotoxicity resulting from PDT. A model to explain the basis for the improved efficacy was developed and is being tested by study of homograft and xenograft tumors in vivo and in multicellular tumor spheroids in vitro.