Boron neutron capture therapy (BNCT) is a new cancer treatment modality that is based on a nuclear reaction occurring between boron atoms concentrates within a tumor and a neutron beam. Since the alpha particles and Li (lithium) nuclei generated by the reaction of 10B (n, α) 7Li, have a short range (less than the diameter of a cell), BNCT can selectively destroy tumor cells in which this reaction occurs without serious damage to the surrounding normal cells. BNCT for unresectable locally advanced and/or recurrent head and neck cancers using an accelerator-based BNCT system was approved by the Japanese government for coverage by the national health insurance program in June 2020. Entire tumors could be expected to be irradiated with at least 20 Gy-Eq. (D80 >20 Gy-Eq, calculated based on a tumor/blood boron concentration ratio of 2.5). This treatment is contraindicated in patients with a high risk of carotid artery rupture and infectious meningitis. We have treated 150 unresectable head and neck cancer cases who met the entry criteria between June 2020 and March 2023. We propose to investigate the short- and long-term outcomes of BNCT and establish appropriate indications for this treatment in patients with recurrent/unresectable head and neck cancer.
