Risk of skin tumors in psoralen- and ultraviolet A-treated patients.

From 1973 to 1981, the clinical data of 1,136 patients with psoriasis and another 1,210 with various skin tumors were accessioned with the aid of computerized data files. Skin tumors and psoriasis occurred in 48 patients. After psoralen plus 320-400 nm UV (PUVA) therapy for psoriasis was introduced in 1976, 381 patients with this disease were treated. Follow-up data revealed no change in the tumor incidence rate after this treatment began. Age-related calculations of the relative probabilities for the presence of skin cancer in patients with psoriasis after PUVA revealed a grossly normal pattern (which appeared to be unaffected by PUVA). We observed a skin tumor in 2 patients 5 years after PUVA therapy.