Photodynamic Therapy

PHOTODYNAMIC THERAPY

Porphyrins are potent photosensitizing intermediates in heme synthesis and are thought to accumulate in malig-nant cells. This feature is used in photodynamic therapy, in which a synthetic porphyrin is administered and the patient is exposed to visible light. This modality has been shown to be effective in treating basal cell and squamous cell skin cancers, although a limiting toxicity has been that patients remain extremely photosensitive for weeks after treatment because of the long elimina-tion half-life of the porphyrin analogues.