consisting of surgery followed by chemotherapy with temozolomide (tmz) and conventional radiation therapy. they were candidates for treatment with bnct because their tumors had recurred and were progressing in size. they received an intravenous infusion of a proprietary formulation of 10b-enriched boronophenylalanine ("borofalan," stellapharma corporation, osaka, japan) prior to neutron irradiation. the primary endpoint of this study was the 1-year survival rate after bnct, which was 79.2%, and the median overall survival rate was 18.9 months. based on these results, it was concluded that c-bns bnct was safe and resulted in increased survival of patients with recurrent gliomas. although there was an increased risk of brain edema due to re-irradiation, this was easily controlled. as a result of this trial, the sumitomo accelerator was approved by the japanese regulatory authority having jurisdiction over medical devices, and further studies are being carried out with patients who have recurrent, high-grade (malignant) meningiomas. however, further studies for the treatment of patients with gbms have been put on hold pending additional analysis of the results. treatment of recurrent or locally advanced cancers of the head and neck katsumi hirose and his co-workers at the southern tohoku bnct research center in koriyama, japan, recently have reported on their results after treating 21 patients with recurrent tumors of the head and neck region. all of these patients had received surgery, chemotherapy, and conventional radiation therapy. eight of them had recurrent squamous cell carcinomas (r-scc), and 13 had either recurrent (r) or locally advanced (la) non-squamous cell carcinomas (nscc). the overall response rate was 71%, and the complete response and partial response rates were 50% and 25%, respectively, for patients with r-scc and 80% and 62%, respectively, for those with r or la scc. the overall 2-year survival rates for patients with r-scc or r/la nscc were 58% and 100%, respectively. the treatment was well tolerated, and adverse events were those usually associated with conventional radiation treatment of these tumors. these patients had received a proprietary formulation of 10b-enriched boronophenylalanine (borofalan), which was administered intravenously. although the manufacturer of the accelerator was not identified, it presumably was the one manufactured by sumitomo heavy industries, ltd., which was indicated in the acknowledgements of their report. based on this phase ii clinical trial, the authors suggested that bnct using borofalan and c-bens was a promising treatment for recurrent head and neck cancers, although further studies would be required to firmly establish this. the future clinical bnct first was used to treat highly malignant brain tumors and subsequently for melanomas of the skin that were difficult to treat by surgery. later, it was used as a type of "salvage" therapy for patients with recurrent tumors of the head and neck region. the clinical results were sufficiently promising to lead to the development of accelerator neutron sources, which will be used almost exclusively in the future. challenges for the future clinical success of bnct that need to be met include the following: optimizing the dosing and delivery paradigms and administration of bpa and bsh. the development of more tumor-selective boron delivery agents for bnct and their evaluation in large animals and ultimately in humans. accurate, real time dosimetry to better estimate the radiation doses delivered to the tumor and normal tissues in patients with brain tumors and head and neck cancer. further clinical evaluation of accelerator-based neutron sources for the treatment of brain tumors, head and neck cancer, and other malignancies. reducing the cost.