Risks of cancer associated with long-term exposure to PUVA in humans: current status--1991.

Since 1975 oral 8-methoxypsoralen administered in association with ultraviolet-A radiation (UVA), (PUVA) has been widely used to treat psoriasis and other cutaneous diseases. PUVA is mutagenic, and in animals carcinogenic. Prospective study of a cohort of patients with psoriasis who were first treated with PUVA in 1975-1976 has provided data on the carcinogenic risk of this treatment. There is a dose-dependent increase in the risk of squamous cell cancer of the skin associated with exposure to PUVA. A recent large-scale Swedish study confirmed this association. The risk of squamous cell cancer of the genitals of males exposed to high doses of PUVA is especially high. A consistent, confirmed, and significant relationship of exposure to PUVA to other types of malignancies in man has not been established. Although highly effective in the treatment of psoriasis, the risk of squamous cell cancer associated with long-term therapy with PUVA must be considered in determining when this therapy is appropriate for an individual patient. Additional study of PUVA-treated patients will better define the full spectrum of the carcinogenic risk of PUVA therapy and the clinical behavior of tumors that arise in association with this treatment.