title: 308-nm excimer laser for the treatment of psoriasis: a dose-response study.
abstract: OBJECTIVE
  To determine the dose-response relationship of excimer laser-generated 308-nm UV-B radiation for treating psoriasis.
  
  
  METHODS
  Pilot study with a before-after design.
  
  
  METHODS
  A university dermatology service.
  
  
  METHODS
  Thirteen consecutive patients with at least 4 large, stable psoriasis plaques.
  
  
  METHODS
  Excimer laser-generated 308-nm UV-B radiation was given to each 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) were 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 severity index score was determined for each area before, every 2 weeks during, and 2 and 4 months after treatment.
  
  
  RESULTS
  The mean+/-SD MED was 203.03+/-57.84 mJ/ cm2. Treatment with high 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 remission.
  
  
  CONCLUSIONS
  With 308-nm UV-B radiation generated by an excimer laser, it is possible to clear psoriasis with as little as 1 treatment with moderately long remission. In contrast to traditional phototherapy techniques, this handheld excimer laser UV-B therapy is selectively directed toward lesional skin, thus sparing the surrounding normal skin from unnecessary radiation exposure. Treatment of other inflammatory diseases and limited psoriasis seems reasonable to pursue with this modality.
authors.affiliation: Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
authors.forename: P
authors.initials: P
authors.lastname: Asawanonda
authors.forename: R R
authors.initials: RR
authors.lastname: Anderson
authors.forename: Y
authors.initials: Y
authors.lastname: Chang
authors.forename: C R
authors.initials: CR
authors.lastname: Taylor
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D053685:Laser Therapy; D010865:Pilot Projects; D011565:Psoriasis / Q000532:radiotherapy*; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014467:Ultraviolet Therapy / Q000379:methods*