Treatment with UV-B for psoriasis and nonmelanoma skin cancer -: A systematic review of the literature

Background: In a cost-effectiveness study currently being conducted of short-contact anthralin treatment for psoriasis in an outpatient setting as compared with the standard treatment with UV-B radiation, the excess incidence (IDD) of skin cancer due to exposure to UV-B could not be ascertained because the study did not last long enough. A meta-analysis of published data was deemed appropriate. Objective: To quantify the IDD of nonmelanoma skin cancer as a function of the total dose of UV-B and specific for time since first exposure, age at first treatment, and other treatments received. Methods: Systematic review of the literature with metaanalysis of all available evidence published in English, French, German, or Dutch between 1980 and 1996. Results: Four articles contained information that enabled us to calculate an overall IDD of nonmelanoma skin cancer. The estimates varied between -0.6 and 2 extra skin cancers per 100 patients with psoriasis treated with UV-B phototherapy per year. However, these estimates were calculated under several assumptions, and do not allow for the construction of a dose-response model specific for time since exposure or age at first treatment. A model based on animal data suggests that a total of 5 excess skin cancers can be expected per 100 treated in the 60 years after the start of treatment with 500 minimum effective doses of UV-B per year from age 25 years. Conclusions: The available evidence is insufficient for quantifying the IDD of nonmelanoma skin cancer in patients with psoriasis treated with UV-B radiation. However, it seems unlikely that the excess risk exceeds 2% per year. As yet, it is not possible to assess at what level of exposure this IDD occurs, or how long after exposure excess risk is present.