BNCT to Treat Glioma That Has Progressed Following Radiotherapy

Overview

Boron Neutron Capture Therapy (BNCT) is an experimental radiation therapy technique which is based on the principle of irradiating boron atoms with neutrons. When neutrons have relatively low energy, boron atoms that have been targeted to cancerous tissue using a suitable boron carrier (an amino acid derivative called BPA, boronophenylalanine) will capture the neutrons. As a result from the neutron capture the boron atoms will split into two, producing helium and lithium ions. The helium and lithium ions, in turn, have only a short pathlength in tissue (about 5 micrometers) and will deposit their cell damaging effect mainly within the tumor provided that the boron carrier (BPA) has accumulated in the tumor. In practice, the study participants will receive BPA as an approximately 2-hour intravenous infusion, following which the tumor is irradiated with low energy (epithermal) neutrons obtained from a nuclear reactor at the BNCT facility. BNCT requires careful radiation dose planning, but neutron irradiation will last approximately only for one hour. In this study BNCT is given once. The study hypothesis is that anaplastic astrocytomas and glioblastomas that have recurred following conventional radiotherapy might accumulate the boron carrier compound, and might respond to BNCT.

This is a single BNCT-facility, non-randomized, non-comparative, prospective, open-label, phase I/II study to determine the value of BNCT in the treatment of inoperable, irradiated, progressing anaplastic astrocytomas or glioblastomas following conventional radiation therapy. The neutron irradiation site is the FiR 1 reactor site, located at Otaniemi, Espoo, Finland, about 6 kilometers from the Helsinki University Central Hospital, Helsinki, where patient evaluation and post-irradiation care will take place. BPA is infused as a fructose complex (BPA-F) into a peripheral vein over 2 hours prior to neutron irradiation. Blood samples will be taken before starting the BPA infusion, and thereafter at 20 to 40 minute intervals during the infusion, following infusion, and after delivering neutron irradiation to monitor the blood boron concentration. The blood samples will be analyzed for boron to estimate the average blood boron level during neutron irradiation. A minimum tumor dose of 17 Gy (W) is given while limiting the normal brain maximum peak dose to 8 Gy (W), and the average normal brain dose to 6 Gy (W). The first 10 patients will be given BPA 290 mg/kg, following which the BPA dose will be escalated in cohorts of 3 subjects gradually up to 450 mg/kg, provided that protocol-specified unacceptable toxicity will not occur. All patients will be evaluated for response using CT or magnetic resonance imaging (MRI).