[Photodynamic therapy in urology. Biologic and pathologic mechanisms of action]

Photodynamic Therapy (FDT) is a minimally invasive therapeutic modality extraordinarily useful. In urology, FDT is very useful and may be applied through endoscopes or directly, with excellent results obtained for the diagnosis and treatment of bladder tumors, in the treatment of prostate cancer and its recurrences, and in the treatment of dermatological premalignant lesions and carcinomas of the penis. FDT is founded on the use of photosensitizing products which selectively accumulate in tumor tissues. The irradiation of these tissues with a proper wavelength light (generally in the red region of the visible spectrum lambda > or = 600 nm) produces the formation of oxygen reactive species with cytotoxic effects leading to selective death of neoplastic cells, and tumor regression. The main advantage of FDT is the restriction of cellular damage to the irradiation area, with the associated decrease of secondary effects on healthy tissues near the tumor, on the contrary to what happen with other conventional therapies for some tumors of the urinary tract. Moreover, FDT may be used in combination with radiotherapy and chemotherapy.