Theoretical Basis

BNCT (Boron Neutron Capture Therapy) is a binary radiation therapy modality. BNCT is based on a nuclear fission reaction that occurs when a stable boron-10 isotope captures a low energy (< 0.5 eV) neutron, generating two highly ionisating particles: an alpha (4He) particle and a lithium (7Li) ion. The path lengths of the alpha particle and the lithium ion are short, 9 μm and 5 μm, respectively. Therefore, most of the radiation effect will be targeted within the boron-10 containing (tumor) cells.

The effectiveness of BNCT depends on the boron-10 concentration within the cell. A selective irradiation of tumor cells can be achieved using a suitable boron-10 containing compound, such as 4-dihydroxylboryl-L-phenylalanine (L-BPA). Using L-BPA it is possible to deliver high concentrations of boron to the tumor relative to the surrounding normal tissues. L-BPA is an amino acid analogue of the naturally occurring amino acids phenylalanine and tyrosine. L-BPA can penetrate the blood-brain barrier, and it is thus a suitable boron carrier compound also for brain tumor treatments.

Due to the limited aqueous solubility of pure L-BPA, L-BPA complexed with fructose (L-BPA-f) is used for intravenous infusions.