Boronophenylalanine (BPA)-Based Boron Neutron Capture Therapy (BNCT) in the Treatment Head and Neck Tumors

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 will be repeated, and the 2 treatments will be given 3 to 5 weeks apart. The study hypothesis is that head and neck cancers 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, open-label, phase I to II trial to determine the value of BNCT in the treatment of inoperable, irradiated, locally advanced cancers of the head and neck region. An attempt to perform 18F-labeled boronophenylalanine (18F-BPA) SPECT or PET imaging will be made before BNCT. Patients whose tumor uptake is \>2.5 times that of the corresponding normal head and neck tissue will be enrolled, and treated with a single fraction BPA-based BNCT twice, 3 to 5 weeks apart. Another 18F-BPA SPECT or PET study may be performed 1 to 3 months after BNCT to determine the SPECT/PET response. 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. Prior to BNCT, BPA is infused as a fructose complex (l-BPA-F) into a peripheral vein over 2 hours. Blood samples will be taken for monitoring whole blood boron concentration before starting the BPA infusion, and thereafter at 20 to 40 minute intervals during the infusion, following infusion, and after delivering neutron irradiation. The blood samples will be analyzed for blood boron concentration to estimate the average blood boron concentration during neutron irradiation. All patients will be evaluated for response using CT or magnetic resonance imaging (MRI).