The effect of ultrasound-induced hyperthermia combined with local x-irradiation in pre- and posttransplantation treatment of the line 1 lung carcinoma

Pathogen-free Balb/c (14 to 16 weeks old) female mice were injected with 10⁶ tumor cells in the left thigh. Preliminary experiments were done to determine the temperature rise and the thermal distribution within the tumor-bearing thigh. The temperature at the surface of the femur was assumed to be at least equal to the temperature measured by the thermocouple inserted at the center of the thigh. The skin temperature remained a few degrees lower than the temperature of the tumor.

The legs of each group of animals were treated on day seven or day eight after tumor transplantation with one of the five treatment modalities: ultrasound for 60 minutes, ultrasound for 30 minutes, 7000 rad X-irradiation, ultrasound for 60 minutes plus 7000 rad, ultrasound for 30 minutes plus 7000 rad. The ultrasound treatments were given immediately prior to the X-irradiation treatments. Ultrasound alone did not have an effect on tumor growth rate and did not enhance the effect of 7000 rad on tumor growth.

To determine the effects of ultrasound-induced hyperthermia and combined ultrasound-induced hyperthermia and X-irradiation on host-tumor interactions, experiments were designed to measure inhibition of tumor growth after pretransplantation treatment of the tumor bed.

The left thighs of the mice were treated with ultrasound for 30 minutes, 500 rad X-irradiation, or the combined treatments. The treatments were given one day, seven days or 30 days before tumor transplantation. A TBE was demonstrated with an X-irradiation dose of 500 rad, which persisted for at least 30 days. A TBE was also demonstrated after ultrasound exposure for 30 minutes. The effect of the ultrasound exposure was still observable after seven days, but not after 30 days. Enhancement by ultrasound of the TBE by 500 rad was only observed when the treatments were given one day before tumor transplant. The results indicate that the damage to the tissue produced by the ultrasound-induced hyperthermia is different from the damage produced by the X-irradiation.