Radiofrequency Hyperthermia for Malignant Brain Tumors: Preliminary Results of Clinical Trials

Abstract

Abstract Local hyperthermia by 13.56-MHz radiofrequency (RF) capacitive heating was evaluated in 16 patients with malignant brain tumors. Intracranial heating during operation was performed in 4 patients. RF applicators with a cooling system were placed on the cerebral convexity and medial brain surface with the tumor between them. RF power was controlled to maintain the brain temperatures under 40°C. Under this condition, the highest temperature of each tumor varied from 44 to 49°C. After heating for about 60 minutes, 2 tumors showed regression on computed tomographic (CT) scans. Extracranial heating was performed in 12 patients with cerebral glioblastoma. RF applicators were placed on the lateral sides of the scalp and applied to diametrically opposite sides of the tumor. To avoid the influence of the skull on RF conduction, we performed a bilateral craniectomy slightly larger than the applicator at the initial operation. Heating was performed for approximately 60 minutes at each session and was repeated twice a week for a total of 4 to 10 times in combination with radiation and ACNU chemotherapy. No anesthetic agent was used during heating. Brain temperatures were maintained under 42°C. The scalp under the applicators remained at 28-35°C during heating, and no heat injury of the scalp was observed after repeated heating. The highest temperatures of the tumor or cavity after tumor removal were 45-46°C in 3 cases, 43-44°C in 3 cases, 42-43°C in 4 cases, and 40-41°C in 2 cases, respectively. Six of 10 evaluable tumors on CT scan showed regression after treatment. Low density lesions appeared transiently in the RF field in the brains of 2 patients. The present study showed that RF capacitive heating can be used safely to heat malignant tumors in the human cerebrum.