Comparison of photochemotherapy and dithranol in the treatment of chronic plaque psoriasis.

A two-centre trial has been carried out on 224 patients with chronic plaque psoriasis randomly allocated to treatment with a standard dithranol regimen of 8-methoxypsoralen and long-wave ultraviolet light (P.U.V.A.). Lesions in 91% of the 113 in the P.U.V.A. group cleared satisfactorily compared with 82% of 111 in the dithranol group, but clearing took longer (34.4 +/- 1.8 S.E. days) with P.U.V.A. than with dithranol (20.4 +/- 0.9 S.E. days). P.U.V.A. treatment took less patient-time and nurse-time and was more convenient and acceptable to the patients. Patients in whom lesions had failed to clear with dithranol, and some who had needed methotrexate for control, responded satisfactorily to P.U.V.A. A few patients who had failed on P.U.V.A. were treated with dithranol and responded to it. There is a case for the use of P.U.V.A. for patients who would otherwise require methotrexate and those who cannot be managed successfully with dithranol. There is also no reason to withhold P.U.V.A. in patients of 60 years or above with chronic plaque psoriasis. However, despite its superiority in terms of cost and patient acceptability, P.U.V.A. cannot be recommended as the first line of treatment for patients with uncomplicated, dithranol-responsive plaque psoriasis until there is more information on relapse-rate and toxicity.