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 meta-analysis 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.