Radiofrequency Interstitial Hyperthermia for Brain Tumor : Development of the Heating System and Clinical Application

We have developed an interstitial heating system using 13.56MHz radiofrequency (RF) antennas for malignant brain tumor. The stainless needle coated by gold with diameter of 1.0mm was used as the antenna. The needle was insulated by silicon except the electrode and its diameter was 1.3mm. A single or multiple (2～4) antennas were inserted into the brain tumor using a CT-guided stereotactic apparatus. The temperature of the brain and the tumor were monitored by the copper-constantan thermocouple sensors. The RF interstitial hyperthermia was performed on 30 patients with malignant brain tumors, 22 malignant gliomas (10 primary and 12 recurrent), 7 metastatic tumor and 1 malignant lymphoma. The rim of the tumors which were defined by contrast enhanced CT was heated at 42.5～43.0℃ for 60 minutes. The heating was repeated 3～9 (mean 5) times, once or twice a week, combined with conventional radiation or ACNU chemotherapy. The recurrent gliomas were treated with heat alone. The patients complained no local pain or heat sensation and well tolerated the repeated heating. No major complication occurred except liquorrhea in 2 cases, subcutaneous infection in one case, intratumoral hemorrhage in one case and transient neurological symptoms in 2 cases. The anti-tumor effects were evaluated by CT and the treated tumors showed CR in 8, PR in 10, ST in 9 and PD in 3 cases, respectively. In most of CR cases, the perifocal low density lesion also disappeared. The RF interstitial hyperthermia seemed to be effective in treatment of malignant brain tumors. This technique is less invasive and the tumors in aged or poor risk patients as well as deep-seated tumors can be good candidates for the application