Boron neutron capture therapy for malignant gliomas

Abstract

Boron neutron capture therapy (BNCT) represents a promising modality for a relatively selective radiation dose delivery to the tumour tissue. Boron-10 nuclei capture slow ‘thermal’ neutrons preferentially and, upon capture, promptly undergo ¹⁰B(n,α)⁷Li reaction. The ionization tracks of energetic and heavy lithium and helium ions resulting from this reaction are only about one cell diameter in length (∼ 14 μm). Because of their high linear energy transfer (LET) these ions have a high relative biological effectiveness (RBE) for controlling tumour growth. The key to effective BNCT of tumours, such as glioblastoma multiforme (GBM), is the preferential accumulation of boron-10 in the tumour, including the infiltrating GBM cells, as compared with that in the vital structures of the normal brain. Provided that a sufficiently high tumour boron-10 concentration (∼10⁹ boron-10 atoms/cell) and an adequate thermal neutron fluence (∼ 10¹² neutrons/ cm²) are achieved, it is the ratio of the boron-10 concentration in tumour cells to that in the normal brain cells that will largely determine the therapeutic gain of BNCT.

Key Words:

• boron neutron capture therapy
• boronophenylalanine
• glioblastoma multiforme