Topical aminolaevulinic acid-based photodynamic therapy as a treatment option for psoriasis? Results of a randomized, observer-blinded study

Background Topical aminolaevulinic acid-based photodynamic therapy (ALA-PDT) hits recently been tried in small open studies for several inflammatory dermatoses including psoriasis. Objectives The purpose of this randomized, within patient comparison study was to investigate whether topical ALA-based PDT using a range of light doses can induce a satisfactory response in localized psoriasis. Patients and methods Twenty-nine patients with chronic plaque type psoriasis were enrolled in the study. After keratolytic pretreatment three psoriatic plaques in each patient were randomly allocated to PDT with 1% ALA and a light dose of 5 J cm(-2), 10 J cm(-2) or 20 J cm(-2), respectively. Treatment was performed twice weekly until complete clearance or for a maximum of 12 irradiations. As a measure of clinical response the psoriasis severity index (PSI) of the three target plaques was assessed separately by an observer blinded to the treatment at baseline, before each PDT treatment and 3-4 days after the last irradiation. Results Eight patients withdrew prematurely from the study. Keratolytic pretreatment alone reduced the baseline PSI in all three dose groups by about 25%. Subsequent PDT with 20 J cm-2 resulted in a final reduction of PSI by 59%, PDT with the lower doses of 10 J cm(-2) and 5 J cm(-2) decreased the baseline PSI by 46% and 49%, respectively. The difference in clinical efficacy between 20 J cm(-2) and 10 J cm(-2) or 5 J cm(-2) was statistically significant (P = 0.003; P = 0.02), whereas no difference was found between 10 J cm(-2) and 5 J cm(-2) (P = 0.4). All patients reported some degree of PDT-induced stinging or burning during irradiation. Conclusions The unsatisfactory clinical response and frequent occurrence of pain during and after irradiation renders topical ALA-based PDT an inadequate treatment option for psoriasis.