Photocarcinogenesis: measuring the reproducibility of a biologic response to ultraviolet radiation exposure in mice.

New drugs undergo safety evaluations of many types. For some drugs, a photocarcinogenesis study forms one of the elements in the overall toxicology package. Photocarcinogenesis studies are designed to evaluate a drug's ability to modify the growth and development of ultraviolet radiation (UVR)-induced skin tumors in albino hairless mice. "Exposure control" groups in such studies receive the UVR, either alone, or in combination with the "vehicle" or carrier associated with each study. This report presents skin tumor data from control groups compiled from nine consecutive studies conducted at this testing facility. The endpoints evaluated included median tumor onset, mortality-free prevalence and tumor yield. "Historical control data" are considered essential for designing, monitoring, interpreting and evaluating studies of a given type. In addition, a compilation of such control data can illustrate trends or provide measures of reproducibility more reliably than can individual studies. This data set shows how clearly the UVR-induced skin tumor onset time is dependent on UVR dose, how skin tumors develop sooner in female mice than in male mice at a low UVR exposure dose, and that topical administration of certain vehicle formulations can enhance photocarcinogenesis.