The feasibility and toxicity of the second course of boron neutron capture therapy in recurrent head and neck cancer patients.

The feasibility and safety of a second course of boron neutron capture therapy (BNCT) are unknown. In this study, we retrospectively analyzed the treatment outcomes and toxicities in recurrent head and neck cancer (RHNC) patients who underwent BNCT twice at Southern TOHOKU BNCT Research Center. In total, 33 patients who underwent BNCT twice for RHNC at Southern TOHOKU BNCT Research Center between June 2020 and March 2024 were included. The indications for second BNCT were local recurrence or residual tumor after the first course. Eligible patients either declined salvage surgery or had no curative treatment options other than second BNCT. The median age was 65 years (range, 23-84 years), and the median interval from the first to the second BNCT was 4.1 months (range, 2.3-14.2 months). The median follow-up period after second BNCT was 27.3 months (range, 3.8-60.4 months), and the median survival time after second BNCT was 33.6 months. The 1-year/2-year overall survival and local control after second BNCT were 81.8%/57.1% and 38.3%/22.3%, respectively. The response rates to the first and second courses of BNCT were 81.8% and 70%, respectively. Acute and late Grade 3 or higher toxicities were observed in 5 (15.1%) and 20 patients (60.6%), respectively. Only one patient developed Grade 5 aspiration pneumonia. A second course of BNCT developed a high incidence of late Grade 3 or higher toxicities with limited clinical benefit. Therefore, it may be considered only in carefully selected patients without alternative treatment options.