Relapse Rate and Duration of Therapeutic Effect of Oral Psoralen plus Ultraviolet a (PUVA) in the Treatment of Plaque-type Psoriasis: Original Data Utilizing Standardized Measures of Effect Duration

Abstract

Background Treatments with long duration of therapeutic effects are ideal for the long-term treatment of psoriasis. This study evaluates psoralen plus ultraviolet light A (PUVA) therapy using standardized definitions of relapse and durability of therapeutic effect. Objectives The purpose of this study was to evaluate the relapse rate and duration of therapeutic effect for PUVA patients who achieved at least 75% reduction in the Psoriasis Area and Severity Index (PASI 75) score after 12 weeks of treatment. Methods This study involved 40 patients with psoriasis; 30 received PUVA and 10 received UVA with placebo for 12 weeks during the double-blind treatment phase. During the post-treatment follow-up, patients who achieved PASI 75 after 12 weeks of PUVA were followed for 48 weeks without treatment to evaluate for relapse (time when subjects return to ≤50% reduction in baseline PASI) and durability of therapeutic effect (time from stopping treatment until 50% of improvement in PASI from the treatment is lost). Results Using per-protocol analysis, 18 out of the 21 patients (86%) who completed the double-blind treatment phase achieved PASI 75 after 12 weeks of PUVA. None of the placebo-treated patients achieved PASI 75. Of the patients who reached PASI 75 after 12 weeks, 89% (16/18) did not relapse after 12 weeks, 69% (11/16) did not relapse after 24 weeks, and 36% (5/14) did not relapse after 48 weeks follow-up. Of the patients who relapsed during the 48-week follow-up, the median time to relapse was 32 weeks. The durability of therapeutic effect was at least 12 weeks, 24 weeks, and 48 weeks respectively in 100% (18/18), 75% (12/16) and 42% (6/14) of the patients. Limitations The study was relatively small with only 14 patients completing the total follow-up period and per-protocol analysis was used. In addition, the patients were generally younger and less severe than those evaluated in biologic studies. There was no direct head-to-head comparison with other treatment modalities to evaluate relative relapse rates. Conclusions The study results support previous reports in the literature and the general clinical impression that PUVA provides prolonged duration of response in patients with plaque-type psoriasis.