Thermotherapy of ${\rm VX}_{2}$ Rabbit Carcinoma: I: Augmentation by Irradiation

An induction-type radiofrequency generator was used to heat thigh implants of the ${\rm VX}_{2}$ rabbit carcinoma. The tumor temperature could be easily raised to over 50°C, while the temperature of normal adjacent muscle generally remained at about 43°C. The marked hypovascularity of the tumor, as demonstrated angiographically, probably explains this disproportionate hyperthermic reaction to administered heat. Twenty-five untreated rabbits succumbed to their tumors after a mean interval of 38 days. Of 24 rabbits with tumors heated to between 48 and 50°C for 30 to 45 min, 5 (21%) were permanently cured. Of 10 rabbits treated with 1000 R in a single dose, none were cured. Of 12 rabbits treated with 1000 R, followed after 3.5 hr with 30 min of heating to 48-49°C, 11 were locally cured. Thus a synergistic effect between hyperthermia and irradiation was demonstrated.