The feasibility of combining local heat treatment with wholebody hypothermia in an effort to improve therapeutic gain was assessed. Superficial, non perfused phantom tumors were fashioned in eight anesthetized mongrel dogs by transplantation of the spleen from the abdomen to a subcutaneous site on the hind limb. After pretreatment of the animal with the vasodilator hydralazine (0.5 mg/kg, IV) to enhance normal tissue perfusion, the spleen implant was heated with a 2450-MHz microwave diathermy apparatus, first with the animal's core body temperature in the normal range (39°C) and then after the animal had been packed in ice to reduce core temperature to 30°C. Applied power density and temperatures in both the phantom tumor and underlying muscle tissue were recorded during brief interruptions of diathermy until steady-state temperatures had been achieved. Under normothermic conditions with time-averaged applied power of 0.038 W/ml to phantom tumor and 0.014 W/ml to underlying muscle, tumor temperature rose to 45.9 ± l.8°C, while muscle temperature remained at 40.5 ± 0.7°C. During whole-body hypothermia applied power could be increased to 0.114 W/ml in phantom tumor and to 0.025 W/ml in muscle. Muscle temperature rose only to 33.8 ± l.6°C, while that of the nonperfused phantom tumor rose to 53.6 ± 4.3°C with systemic hypothermia. These results are in agreement with predictions based on the bioheat transfer equation, i.e., heat extraction from well-perfused normal tissues is greatly augmented by cooling of the arterial blood, allowing greater power input to the tumor-bearing region, higher tumor temperatures, and enhanced therapeutic gain during local heat treatments of poorly perfused tumor nodules.
cancer, heat therapy, hyperthermia, therapeutic advantage, tumor, safety
Date of this Version
Babbs, Charles F.; Voorhees, William D. III; Clark, Robert R.; and DeWitt, David P., "Use of Combined Systemic Hypothermia and Local Heat Treatment to Enhance Temperature Differences Between Tumor and Normal Tissues" (1985). Weldon School of Biomedical Engineering Faculty Publications. Paper 102.