NI-04 Evaluation of post boron neutron capture therapy for recurrent meningioma using fluoride-labeled boronophenylalanine PET

We have applied boron neutron capture therapy (BNCT) for 46 recurrent high grade meningiomas (HGM). Twelve cases among them, fluoride-labeled boronophenylalanine positron emission tomography (18F-BPA-PET) were utilized before and after BNCT to evaluate the tumor activity. The lesion to normal brain (L/N) ratios of 14 lesions of these 11 cases were investigated. In all cases L/N ratio decreased after BNCT. The L/N ratio of recurrent (HGM) was 3.2±1.5 (mean±SD) before BNCT and 2.1±0.6 after that. In contrast enhanced MRI, 13 out of 14 lesions shrank or unchanged at least 3 months after BNCT, while one lesion transiently increased and then decreased within 3 months, showing pseudoprogression. In addition, 6 of 12 lesions which could be followed on MRI for more than 3 months progressed after 8 months. 4 of them were performed PET at the time of progressing. The L/N ratio of 2 progressing lesion which were diagnosed as recurrence due to continuously increasing were showed increasing. The L/N ratio of the other 2 lesions which were diagnosed radiation necrosis due to unchanged or shrinkage showed decreasing. Moreover, some systemic metastasis detected in PET image. F-BPA-PET seems to be useful for the evaluation of tumor activity.