TOPICAL PHOTODYNAMIC THERAPY IN DERMATOLOGY

Although photodynamic therapy (PDT) was first used in the treatment of skin diseases, phase-III-clinical trials were primarily conducted for the treatment of bladder cancer, endobronchial and oesophageal carcin oma. In dermatology PDT has most extensively been used for the treatme nt of malignant cutaneous lesions. Up to now those patients have been treated systemically with first-generation photosensitizers. However, prolonged skin photosensitivity is a major disadvantage of this form o f therapy. Topical PDT utilizing a variety of sensitizers bypass this unwanted effect. Of strong interest is 5-aminolevulinic acid (ALA), fi rst introduced in the topical PDT of skin disorders in 1990 by Kennedy and co-workers. ALA serves as a pro-drug, i.e. the active photosensit izing compound is protoporphyrin IX which is synthesized in vivo after exogenous application of ALA. In several oncologic and non-oncologic skin conditions including non-melanoma skin cancer, premalignant condi tions like actinic keratoses and in psoriasis, topical ALA-PDT showed it's effectiveness. Besides ALA, new sensitizers like benzoporphyrines and porphycenes may play a role in topical PDT. However, at the momen t, there is still a need for comparative studies and standardized ther apeutic protocols to define the place of topical PDT in Dermatology.