Boron neutron capture therapy: Preliminary study of BNCT with sodium borocaptate (Na2B1 2H1 1SH) on glioblastoma

To plan the optimal BNCT using BSH for glioblastoma patients, the¹⁰B concentration in tumor and blood was investigated in 11newly diagnosed glioblastoma patients. All patients received 20 mg BSH/kgbody weight 2.5–16 hrs prior to tumor removal. The quantitativedistribution of ¹⁰B was determined by prompt gamma rayspectrometry and/or -track autoradiography. ¹⁰Bdistribution in tumors was heterogeneous, ± 25% of scatteringat the microscopic level, and the distribution was also heterogeneous at thetissue level. ¹⁰B concentration in blood decreased inbi-exponential decay as a function of the time after the end of theadministration. The T/B ratio showed non-exponential increase with largevariation. The maximum T/B ratio would be around 1. The tumor/normal brain(T/N) ratio of ¹⁰B concentration was 11.0 ± 3.2. The¹⁰B content in normal brain is originated in vascular¹⁰B in parenchyma, since the ¹⁰B content innormal brain to blood (N/B ratio) being compatible with the blood content inparenchyma. These values allow for BNCT, using thermal neutrons, on braintumors located less than approximately 3.3 cm in depth from the brainsurface of neutron incidence, providing that the dose on the normalendothelium is controlled to less than the tolerance limit. In ourpreliminary study of BNCT, a 31% 3-year survival was achieved overall for 16 glioblastoma patients and a 50% 2-year survival wasachieved on 8 glioblastoma patients in our recent dose escalation studybased on these data.