Exploring BNCT as a Novel Approach for Metastatic Spinal Tumor Management ^†

[Background] Boron neutron capture therapy (BNCT) is a particle beam therapy that enables the precise targeting of tumors at the cellular level. Building on the success observed in nuclear reactors, BNCT exhibits potential as a therapeutic approach for managing invasive brain tumors, including malignant gliomas and high-grade meningiomas. Metastatic spinal tumors have been treated by surgical removal, radiation therapy, and a variety of other multidisciplinary therapies. However, none of them has been successful in overcoming this metastatic disease. This study aimed to assess the efficacy of BNCT in treating metastatic spinal tumor using a mouse model.

[Methods] In vitro experiment: neutron irradiation was applied to A549 human lung carcinoma cells with (BNCT group) or without p-boronophenylalanine (BPA) 10 µg Boron/mL for 24 h exposure before irradiation (hot control group) for 0 to 30 min. The cell killing effect was assessed by a colony forming assay. In vivo experiment: an A549 subcutaneous tumor was removed and implanted into the lumbar lamina, where it was partially resected. A few weeks later, metastatic spinal tumor models were successfully established. For the biodistribution of boron, after 2.5, 6, or 24 h of intravenous BPA administration (250 mg/mouse body weight), the metastatic spinal tumor models were sacrificed and the boron concentration of the tumor and each organ measured using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES).

[Results] In vitro neutron experiment: the BNCT group showed a greater cell killing effect than the hot control group. The highest boron accumulation in the tumor was observed at 2.5 h after BPA administration (10.5 µg B/g), and the tumor to normal spinal cord ratio (T/N) was 3.6 and the tumor to blood ratio (T/Bl) was 2.9.

[Conclusions] The findings may indicate that BNCT represents an effective approach in the management of metastatic spinal tumor. We will perform an in vivo neutron irradiation experiment on this model to evaluate the effects of BNCT on survival and neurological function.