This is a single-center, non-randomized, non-comparative, open-label, phase I/II trial to determine safety and efficacy of BNCT in the treatment of nonoperable, irradiated, locally advanced cancers of the head and neck region. Patients will be treated with a single-fraction boronophenylalanine (BPA)-based BNCT. All patients will be evaluated for response using CT or magnetic resonance imaging (MRI).