Effects of moderate hyperthermia on the rabbit sarcoma model

A method of induction of moderate hyperthermia with a plate heater and a direct current energy source was investigated in the VX-2 rabbit sarcoma model. The theoretical distribution of temperature in the rabbit brain was calculated under various heating conditions. The calculated temperatures coincided well with the temperatures of moderate hyperthermia measured by a thermocouple to a depth of 7 mm under the heater. Moderate hyperthermia was induced in the VX-2 sarcoma. Hyperthermia at 40 degrees C for 20 minutes caused no changes in the lesion. Hyperthermia at 45 degrees C for 20 minutes destroyed the lesion partially to a maximum depth of 3 mm. Hyperthermia at 50 degrees C for 20 minutes caused greater destruction, but also caused edema in the lesion and the surrounding normal brain. Hyperthermia at 55 degrees C for 20 minutes caused severe damage in both the lesion and the surrounding normal brain. Comparison of the actual destruction by hyperthermia and the theoretical temperature distribution indicated that hyperthermia at 43 degrees C for 20 minutes was effective against brain tumor, and destruction reached at least 3 mm from the heater.