Enhancement of bleomycin activity against Lewis lung tumors in mice by local hyperthermia.

The cytotoxicity of the drug bleomycin in vitro has previously been shown to be enhanced by hyperthermia. This report demonstrates in vivo a more than additive interaction between local tumor hyperthermia (43 degrees, 60 min) and bleomycin (15 mg/kg s.c.) against s.c.-implanted Lewis lung carcinomas in mice. Local hyperthermia was produced by the application of 2450-MHz microwaves to the region of the tumor without induction of significant whole-body hyperthermia. The combined drug and heat treatments were applied to tumors on Days 4, 7, and 10 following implantation. The response of the tumors to simultaneous treatment was a 17-day growth delay compared with controls, whereas the local hyperthermia and bleomycin individually resulted in only 3- and 4-day growth delays, respectively. If the two treatments were given either 4 or 24 hr apart only an additive effect on growth delay was observed.