Neutron-capture therapy of brain tumours: Neutron sources, neutron- capture drugs, biological tests and clinical perspectives in the Czech Republic
The paper reviews neutron sources, chemical compounds and clinical perspectives of the boron neutron-capture therapy of brain tumours. Special attention is paid to the physical characteristics and biological effectiveness of the epithermal neutron beam constructed at the LVR-15 nuclear reactor at Rez near Prague.
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- "Modern nuclear reactor based epithermal (0.5 eV-10 keV) neutron beams fulfil the requirements for effective BNCT with neutron fluxes of about 10 9 neutrons/cm 2 s (e.g. Perks et al. 1988, Moss 1990, Rogus et al. 1994, Liu et al. 1996, Burian et al. 1997, Moss et al. 1997, Auterinen et al. 2001, Kortesniemi 2002, Seppälä 2002). "
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ABSTRACT: Sodium borocaptate (BSH, Na2Bl2HllSH), a slow neutron-capture compound, was injected into the left forebrain ventricle of 1-week-old rats (150 microg BSH/3 microl phosphate buffered saline). After 90 min, the animals were irradiated by epithermal neutrons (LVR-15 nuclear reactor in Rez near Prague, flux density 8.8 x 10(7) neutrons cm-2 s-1, 8 MW reactor power, 8.2 cGy/min) for 5, 10 or 20 min. The brains were examined histologically 8 h after irradiation. In animals irradiated for 5 to 10 min (41 and 82 cGy-Eq, respectively) lethal damage of cells was found in the external granular layer of the cerebellum and the subependymal layer of the forebrain. Irradiation for 20 min (164 cGy-Eq) caused more extensive destruction of cell populations in these regions and, in addition, dead cells appeared also in the more differentiated postmitotic compartments, namely the deeper layers of the cerebellum, layers II/III of the cerebral cortex and corpus callosum. In the forebrain periventricular layer, the extent of cell damage was declining towards the olfactory bulbs. In intact animals, as well as in those injected only with the 150 microl phosphate buffered saline, the radiation damage was low and limited only to the most sensitive dividing populations of the cerebellum and the forebrain. The study demonstrates a differentiation-dependent damage of the rat brain cells by alpha particles and presents a simple model for evaluation of the biological effectiveness of slow neutron beams constructed for neutron-capture therapy of tumors.
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ABSTRACT: Purpose: A Phase I trial of cranial neutron capture therapy (NCT) was conducted at Harvard-MIT. The trial was designed to determine maximum tolerated NCT radiation dose to normal brain.Methods and Materials: Twenty-two patients with brain tumors were treated by infusion of boronophenylalanine-fructose (BPA-f) followed by exposure to epithermal neutrons. The study began with a prescribed biologically weighted dose of 8.8 RBE (relative biologic effectiveness) Gy, escalated in compounding 10% increments, and ended at 14.2 RBE Gy. BPA-f was infused at a dose 250–350 mg/kg body weight. Treatments were planned using MacNCTPlan and MCNP 4B. Irradiations were delivered as one, two, or three fields in one or two fractions.Results: Peak biologically weighted normal tissue dose ranged from 8.7 to 16.4 RBE Gy. The average dose to brain ranged from 2.7 to 7.4 RBE Gy. Average tumor dose was estimated to range from 14.5 to 43.9 RBE Gy, with a mean of 25.7 RBE Gy.Conclusions: We have demonstrated that BPA-f-mediated NCT can be precisely planned and delivered in a carefully controlled manner. Subsequent clinical trials of boron neutron capture therapy at Harvard and MIT will be initiated with a new high-intensity, high-quality epithermal neutron beam.
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