Radt-37. interim results of accelerator-based boron neutron capture therapy, randomized controlled trial for recurrent and refractory high-grade meningiomas

BACKGROUND High-grade meningiomas (HGMs) recurred after X-ray treatment showed 5.2 months as median progression free survival (mPFS) and only 24.6 months as median overall survival (mOS) from the literatures. Recently, we showed much more excellent OS and PFS using reactor-based boron neutron capture therapy (BNCT) (Neuro-Oncology 24:90-98, 2022). Based on these data, we started “A phase II investigator-lead RCT using accelerator-based BNCT system for refractory recurrent high-grade meningioma”, with the aid of Japanese governmental financial support. METHODS We prepared 2 study arms, BNCT test treatment arm (12 subjects) and control best supportive care arm (6 subjects) in RCT fashion. PFS judged by third party committee was set-up as primary endpoint and PFS judged by investigators themselves and OS of BNCT arm were set-up as secondary endpoints. To diminish ethical problems of this RCT, rescue BNCT is permitted for control group patients, if they showed progress disease during the observation period. Macdonald criteria was adopted for assessment. The first patient-in was August 2019 and the last patient-in was August 2021. Interim results of this trial: Three and two grade 3 subjects were included in BNCT and control arm, respectively. Others were grade 2 subjects. As of April 20, 2023, mPFS judged by investigators showed 90 weeks and 8 weeks for BNCT and control arm, respectively (P = 0.0004). OS-2 year rates of BNCT and control arms are 91.7% and 25%, respectively (p = 0.01) CONCLUSION Primary endpoint, mPFS judged by third party committee is still being closed and unknown, so far, until the end of the trial (August 2024). With regard to secondary endpoints, there are marked differences in both arms in mPFS judged by investigators. Also, OS in BNCT arm is extremely excellent in comparison with EORTC RCT of “trabectedine” and PD-1 blockade reports, just recently appeared.