308-nm excimer laser for the treatment of psoriasis - A dose-response study

Objective: To determine the dose-response relationship of excimer laser-gen erated 308-nm UV-B radiation for treating psoriasis. Design: Pilot study with a before-after design. Setting: A university dermatology service. Patients: Thirteen consecutive patients with at least 4 large, stable psori asis plagues. Interventions: Excimer laser-generated 308-nm UV-B radiation was given to e ach of 4 plaques, which received 1, 2, 4, and 20 treatments, respectively. Untreated areas within each plaque served as controls. Within each plaque, 8 doses based on multiples,of a predetermined minimal erythema dose (MED) w ere tested in distinct sites. The multiples were 0.5 and 1 (low dose); 2, 3 , 4, and 6 (medium dose); and 8 and 16 (high dose). At every treatment, the dose for each site remained fixed at the same MED multiple. A psoriasis se verity index score was determined for each area before, every 2 weeks durin g, and 2 and 4 months after treatment. Results: The mean+/-SD MED was 203.03 +/- 57.84 mJ/cm(2). Treatment with hi gh fluences produced significantly better results than that with medium and low fluences at weeks 4, 6, 8, and 10 (P<.05). At 4 months' follow-up, all sites that received low or medium fluences had recurrences, whereas those that underwent a single treatment at 8 and 16 MED multiples remained in rem ission. Conclusions: With 308-nm UV-B radiation generated by an excimer laser, it i s possible to clear psoriasis with as little as 1 treatment with moderately long remission. In contrast to traditional phototherapy techniques, this h andheld excimer laser UV-B therapy is selectively directed toward lesional skin, thus sparing the surrounding normal skin from unnecessary radiation e xposure. Treatment of other inflammatory diseases and limited psoriasis see ms reasonable to pursue with this modality.