Targeted 307 nm UVB-phototherapy in psoriasis. A pilot study comparing a 307 nm excimer light with topical dithranol

Background Phototherapy is a cornerstone in treatment of moderate‐to‐severe psoriasis. Narrow‐band UVB has been shown to be a potent therapeutic tool. To reduce the potential carcinogenic risk, targeted phototherapy has been developed using excimer lasers or excimer light devices (ELD). Objective The role of excimer light therapy in practice and modes of action are not completely understood. We wanted to investigate a 307 nm ELD for plaque psoriasis in comparison with topical dithranol therapy twice daily. Methods We conducted a pilot trial in 21 adult patients with moderate plaque‐type psoriasis. Two target lesions of comparable size and plaque‐modified Psoriasis Activity and Severity Index (PSI) scores were selected. Lesion A was treated three times using a newly developed 307 nm ELD. Lesion B was treated twice daily with dithranol ointment. The mean period of treatment was 9 days. Clinical evaluation included PSI scores, safety, time needed to treat, and patient's satisfaction. In addition, fluorescence‐remission imaging technique was used for objective evaluation. Results Both treatments improved the PSI score (mean 3.0 points). The treatments were safe but ELD was more convenient for patients. The time needed to treat the target lesion was significantly shorter with ELD. Targeted UVB therapy normalized NADH fluorescence in lesional skin. Conclusions The 307 nm excimer light therapy for plaque type psoriasis was equipotent to twice daily topical dithranol. Efficacy, safety, and convenience suggest that targeted UVB therapy with quasi monochromatic light is a new useful treatment option for patients with limited psoriatic plaques.