Intravascular hyperthermia: experimental study of transcatheter treatment

External hyperthermia has frequently been used to treat superficial malignant tumors. We postulated that transarterial internal hyperthermia may be effective for deeply located hypervascular tumors. We performed intravascular hyperthermia (IVH) for malignant hypervascular tumors that were transplanted into animals and evaluated the resulting histologic changes and antitumoral effects.

We designed a special catheter to heat the injected saline. Sixteen rabbits with hypervascular VX2 tumors ranging from 2 to 2.5 cm in diameter in their left hindlimb muscles served as subjects. IVH was performed via the left femoral artery (temperature = 50 degrees C) in 11 rabbits. Two sessions of IVH were performed during 1 week. Two weeks after the two sessions of IVH, the rabbits were sacrificed and their tumors and feeding arteries were resected. Five control rabbits had 37 degrees C saline infused using the same technique.

The temperature in the central zone of the tumor increased markedly to 42.3 +/- 0.5 degrees C (mean +/- standard deviation), compared with 40.3 +/- 0.4 degrees C and 39.2 +/- 0.5 degrees C in the peripheral zones of the tumor and the surrounding tissue, respectively. Tumor sizes were calculated on angiograms as having decreased by 63 +/- 35% of their initial sizes during the 2 weeks after the two IVH sessions. However, tumor sizes increased to 171 +/- 41% in the control group (p < .01). Necrosis in the peripheral zones of the tumors in the IVH group was more severe than that in the control group (p < .05). Necrosis in the central zones of the tumors in the IVH group was slightly more severe. The surrounding tissue was not damaged. Although the femoral artery was not severely damaged, there was severe damage to the feeding arteries.

IVH reduced the size of hypervascular tumors in our rabbits. The antitumoral effects are attributed to direct damage of the tumor vessels and to the effect of heat on the tumor cells.