Preclinical Validation of the iBNCT001 Accelerator System for Boron Neutron Capture Therapy: In Vitro Efficacy, Beam Quality, and Radiation Safety Evaluation

Boron neutron capture therapy (BNCT) is a binary radiotherapy that is based on nuclear reactions between boron-10 and low-energy neutrons, which enables selective tumor cell killing. Although accelerator-based BNCT systems are increasingly being adopted, each platform requires independent biological validation. Here, we performed an in vitro preclinical evaluation of the linac-based iBNCT001 system employing a beryllium target in combination with the clinically approved boron drug SPM-011 (borofalan (10B)). Three complementary studies were conducted: (i) a cell-based BNCT efficacy study, (ii) a free-beam radiobiological evaluation, and (iii) a radiation leakage assessment using a human-phantom model. BNCT using iBNCT001 and SPM-011 induced clear boron concentration- and dose-dependent reductions in clonogenic survival across multiple tumor cell lines. Free-beam experiments determined a relative biological effectiveness (RBE) of 2.3 for the hydrogen dose component associated with high energy neutrons. In the phantom study, the maximum radiation leakage dose during head irradiation was 1.31 GyEq in the cervical region. Although this study is limited to in vitro biological assessments, the results provide non-clinical evidence supporting the efficacy, beam quality, and biological safety of iBNCT001 for future clinical BNCT applications.