PHOTODYNAMIC THERAPY IN DERMATOLOGY

Photodynamic therapy (PDT) uses exogenously administered or endogenous ly formed photosensitizers activated by light to induce cell death via formation of singlet oxygen and other free radicals. Photodynamic the rapy is increasingly used for the treatment of skin cancers and other indications. The efficacy of PDT depends on the structure of the photo sensitizer, the administration modality, the light source, and the tre atment procedure. We reviewed the most recent clinical and experimenta l developments in PDT research related to dermatology. The substrate u nder most intense investigation in PDT research is delta-aminolevulini c acid (ALA). Photodynamic therapy with topically applied ALA has been shown to be highly efficient in the treatment of cutaneous neoplasms by using intralesionally formed porphyrins as photosensitizers. For so lar keratoses, best response rates have been described. delta-Aminolev ulinic-PDT is also efficient in the treatment of superficial basal cel l and squamous cell carcinomas. In addition, the fluorescence of ALA-i nduced porphyrins under a Wood light is highly selective in neoplastic cutaneous tissue and offers a useful technique in detecting and delin eating skin tumors with ill-defined borders.