Photodynamic Therapy of Bladder Cancer

Abstract

Photodynamic therapy (PDT) is based on interactions between light and a photosensitizer in the presence of oxygen. Photosensitizer-tagged cells are selectively destroyed. Medical interest in the cytotoxic responses of photosensitizers was recorded as long ago as 1900 by Raab (1900), who showed that a nonpigmented protozoan could be sensitized to visible light by the introduction of an appropriate dye (acridine). The protozoans that took up the dye were killed when exposed to sunlight. Neither the dye nor the light alone could achieve this. The use of porphyrins as photosensitizers has quite a long history. The first observation of porphyrin accumulation was made by Policrd (1924). In 1961, a new porphyrin composition, referred to as hematoporphyrin derivative (HPD), was introduced by Lipson et al. (1961). Pioneering efforts in clinical HPD photosensitization were made by Dougherty, who published reports on a series of PDT-treated patients from 1978 onward. (Dougherty et al. 1978; Dougherty 1984). Urologic use of PDT was first reported by Kelly et al. (1975), with the successful destruction of human transitional cell carcinoma in mice.