 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. The first 12 patients are treated using a BPA dose of 290 mgkg, following which the dose of BPA is increased stepwise to 500 mgkg, provided that unacceptable toxicity will not occur. 