Boron-neutron capture therapy for brain tumor. A study on its clinical application and improvement of its efficacy

Boron-neutron capture therapy is composed of thermal neutron radiation and intracellular radiation by α-particle and lithium nucleus. Compared with the conventional radiation therapy with X-ray or γ-ray, the biological effects of α-ray are much larger on the tumor cells and the range distance of α-particle is 5-10 nm, which is much shorter than that of γ-ray. Thus, selective lesioning of tumor cells became possible by using BNCT without generation of large damages in the adjacent normal nerve tissues. The present study was conducted for the improvement of neutron beam and development of new boron compounds. The follow-up data for 84 patients with brain tumor (glioma) by the use of CT or MRI were analyzed to evaluate the efficacy of BNCT. Thus, the subjects were classified into 4 groups based on the extent of response. The numbers of cases in good-response and partial-response group were 37 and 9, respectively. The mean survival period was 640 days ranging 39-8138 days. Thus, the reduction of tumor size or its disappearance were observed in 64% of the subjects, showing a significant efficacy of BNCT for malignant brain tumor. Presently, development of epithermal neutron with high transmittance is underway. (M.N.)