Interstitial hyperthermia of malignant brain tumors by an implant heating system using stereotactic techniques.

Interstitial hyperthermia of malignant brain tumors has been produced by a heated ferromagnetic implant with a low Curie point. Induction heating of the implant, which is stereotactically implanted in a tumor, is obtained by eddy currents in a high-frequency magnetic field. Safe, repeated and long-term treatment of 35 cases of malignant brain tumors has been done using this system. The overall response rate was 31.4%, but the rate for metastatic brain tumors, deep-seated gliomas and others were 50.0, 36.8 and 33.3%, respectively. Deep-seated gliomas were more effectively treated than superficial gliomas by combination with radiation therapy. The common pathological finding was a clearly demarcated coagulative necrosis of ellipsoid shape around the implant.