Boron neutron capture therapy: Preliminary study of BNCT with sodium borocaptate (Na2B12H11SH) on glioblastoma

To plan the optimal BNCT using BSH for glioblastoma patients, the B-10 concentration in tumor and blood was investigated in 11 newly diagnosed glioblastoma patients. All patients received 20 mg BSH/kg body weight 2.5-16 hrs prior to tumor removal. The quantitative distribution of B-10 was determined by prompt gamma ray spectrometry and/or alpha-track autoradiography. B-10 distribution in tumors was heterogeneous, +/-25% of scattering at the microscopic level, and the distribution was also heterogeneous at the tissue level. B-10 concentration in blood decreased in bi-exponential decay as a function of the time after the end of the administration. The T/B ratio showed non-exponential increase with large variation. The maximum T/B ratio would be around 1. The tumor/normal brain (T/N) ratio of B-10 concentration was 11.0 +/- 3.2. The B-10 content in normal brain is originated in vascular B-10 in parenchyma, since the B-10 content in normal brain to blood (N/B ratio) being compatible with the blood content in parenchyma. These values allow for BNCT, using thermal neutrons, on brain tumors located less than approximately 3.3 cm in depth from the brain surface of neutron incidence, providing that the dose on the normal endothelium is controlled to less than the tolerance limit. In our preliminary study of BNCT, a 31% 3-year survival was achieved over all for 16 glioblastoma patients and a 50% 2-year survival was achieved on 8 glioblastoma patients in our recent dose escalation study based on these data.