10148- ACT-7 BORON NEUTRON CAPTURE THERAPY FROM TWO-DIRECTION FOR HIGH-GRADE MENINGIOMAS ACHIEVED BY PATIENT REPOSITIONING AND CONTINUOUS BPA ADMINISTRATION

Abstract BACKGROUND High-grade meningiomas are refractory to repeated surgery and radiotherapy. We have performed boron neutron capture therapy (BNCT) for high-grade meningiomas. We report on BNCT for extensive, deep or multiple lesions in recurrent high-grade meningiomas, using two-directional neutron irradiation in a single machine-time. METHODS BNCT was performed at a reactor power of 5 MW with the Heavy Water Neutron Irradiation Facility in the Institute for Integrated Radiation and Nuclear Science, Kyoto University. The boron compound used was boronophenylalanine (BPA), which was administered intravenously (200 mg/kg/h) for 2-hour before irradiation, followed by continuous BPA administration during irradiation. Those patients were repositioned between the first and second irradiations. Prescribed doses were calculated from the tolerable dose in normal brain and mucosal tissues. RESULTS Two-directional neutron irradiation was planned eight times. The irradiation durations were 40 ± 11.3 min for the first and 34.9 ± 8.7 min for the second. The irradiation interval was 36.7 ± 3.6 min. The second irradiation was interrupted or stopped at 2 cases. The factors for the two-directional irradiation were extensive tumor location, deep midline and multiple lesions. All patients developed treatment-related adverse events within one month, including increased amylase, fever, urine color change and dermatitis. Most adverse events resolved within six months. CONCLUSIONS Two-directional neutron irradiation reduces the dose to normal tissue and allows irradiation of multiple sites, thus ensuring tumor dose to deep midline lesions and allowing irradiation of large or multiple lesions. Adverse events were similar to those seen with BNCT for malignant gliomas at single neutron irradiation, suggesting the safety of two-directional neutron irradiation and continuous administration of BPA. This report may be a pioneer in the use of two-directional neutron irradiation.