Carcinogenicity of combined ultraviolet B radiation and psoralen plus ultraviolet A irradiation treatment of mice.

Overview

Psoralen plus ultraviolet A (PUVA) therapy and UVB phototherapy are frequently used in the treatment of psoriasis and other skin diseases. Both treatments are thought to be carcinogenic, but little is known about their interaction in the induction of skin cancer. Tumors induced in mice treated with both PUVA and UVB, either given sequentially or concurrently, seemed to be more antigenic as a group than tumors treated by PUVA alone, as determined by their lower frequency of growth when transplanted into naive mice. In this study, we treated C3H mice with a subcarcinogenic dose of UVB radiation for 4 weeks, followed by PUVA treatment for 41 weeks (sequential experiment) or with both UVB radiation (minimal carcinogenic dose) and PUVA for 41 weeks (concurrent experiment) and monitored the development of skin cancers. Although a few tumors appeared earlier in the groups treated with both UVB and PUVA in both experiments, no significant differences were observed in the rate of tumor development in mice treated with UVB and PUVA versus those treated with PUVA alone.