Photodynamic therapy in dermatology – an update

Topical photodynamic therapy (PDT) is a well-established treatment modality which has mainly shown to be effective for dermatooncologic conditions like actinic keratoses (AK), Bowen's disease, in situ squamous cell carcinoma and superficial basal cell carcinoma (BCC). However, a therapeutical benefit of PDT is also evident for inflammatory dermatoses like localized scleroderma, acne vulgaris and granuloma annulare. Recent work has been focused on the development and evaluation of topical photosensitizers like the heme precursor 5-aminolevulinic acid (5-ALA) or its methyl ester (methyl aminolevulinate) inducing photosensitizing porphyrins. These drugs do not induce strong generalized cutaneous photosensitization like the systemically applied porphyrins or their derivatives. For dermatological purposes, incoherent lamps or light-emitting diode arrays can be used for light activation. Depending on the applied light dose and the concentration of the photosensitizer either cytotoxic effects resulting in tumor destruction or immunomodulatory effects improving the inflammatory conditions occur. Treating superficial oncologic lesions (tumor thickness <2-3 mm) cure rates achieved by PDT are equal to the cure rates of the respective standard therapeutic procedure. The benefits of PDT are the low level of invasiveness and the excellent cosmetic results after treatment.