Skin tumors in the European PUVA Study. Eight-year follow-up of 1,643 patients treated with PUVA for psoriasis.

In the continuation of the European PUVA Study, 1,643 patients of the original cohort of 3,175 patients enrolled in this prospective study were reevaluated for skin tumors after an average observation period of 96 months. Thirty-six patients with a total of seventy-one tumors (forty squamous cell carcinomas, twenty-three basal cell carcinomas) were observed. In contrast to the U.S. sixteen-center study, we were unable to demonstrate a clinically relevant increase in the risk of tumors induced by psoralens with ultraviolet A (PUVA), and we also failed to show a clear relationship between PUVA exposure and tumor development. Almost all patients with tumors had been exposed to various carcinogens before the initiation of PUVA. No tumors were detected in patients without such prior treatment, although 10% of the patients had received more than 3,000 joules/cm2 total cumulative phototoxic PUVA dose during the observation period. The discrepancy between the results of the U.S. study and our findings may partly be explained by a variety of factors such as a different treatment approach, a different attitude toward sun exposure, and the overall lower incidence of skin cancer in the European population.