Studies of temperature rise in bladder cancer and surrounding tissues during radiofrequency hyperthermia

Temperatures in the tumor on the bladder wall, tumor margin, intravesical urine, rectal cavity and pubic subcutaneous fat tissue (SCFT) were measured in a total of 48 bladder tumor patients during radiofrequency (RF)-capacitive heating of the tumors. There were close correlations (p less than 0.01) between the temperature of the tumor margin and intratumor temperature, between the intravesical temperature and the temperature of the tumor margin, between the RF power applied and the intravesical temperature and also between the thickness and the temperature of SCFT. As long as the thickness of SCFT was 20 mm or less, it was possible to raise the temperature of bladder cancer to 42.5 degrees C or above. The intravesical temperature could be regarded as an indicator for hyperthermia treatment since the intravesical urine temperature of over 42 degrees C implied a therapeutic temperature of 42.5 degrees C or more in the margin of the tumor. Since the intravesical temperature was closely related to the output power, the therapeutic magnitude of the output power could be defined at least as 400 W, by which intravesical urine temperature could exceed 42 degrees C.