Effect of combined treatment with magnetic induction hyperthermia and chemotherapy in a rabbit brain tumor model.

The effects of interstitial magnetic induction hyperthermia alone and in combination with chemotherapy were evaluated in a rabbit brain tumor model. VX2 carcinoma cells were implanted intracerebrally in 28 rabbits. The animals were divided into four groups of seven each, and the experimental protocols were started on the 7th day after inoculation. Group 1 underwent hyperthermia alone by means of implantation of a needle (Fe-Pt alloy) in the tumor, which was maintained at 45 degrees C for 30 minutes. Group 2 received 12.5 mg/kg ACNU intravenously via a lateral ear vein. In Group 3, 10 minutes after injection of ACNU, hyperthermia was induced in the same manner as in Group 1. Group 4 were controls and received no treatment. The four groups were evaluated and compared in terms of length of survival and pathological features of their brain tumors at the time of death. The mean survival times of Groups 1, 2, 3, and 4 were 14.7, 14.7, 17.3, and 12.3 days, respectively. Statistically significant differences were found between Groups 1 and 4 and between Groups 3 and 4, but not between Groups 1 and 2. Pathological findings in the hyperthermia group included necrosis around the implant. The tumor cells surrounding the necrotic area had degenerated and the vessels were dilated and static. Thus, in this rabbit brain tumor model, hyperthermia alone was significantly superior to no treatment, and combined treatment with hyperthermia and chemotherapy was more effective than either treatment alone.