局所再発鼻咽頭癌に対する緩和的ホウ素中性子捕捉療法：後ろ向き研究

Boron neutron capture therapy (BNCT) is a targeted form of particle radiotherapy (RT) that better spares normal tissues than does conventional photon RT. We describe our experience with compassionate-use BNCT for locally recurrent nasopharyngeal cancer (rNPC) after prior radiotherapy.

Data from patients with rNPC who received BNCT outside of clinical trials at the Tsing-Hua Open-Pool Reactor between 2020 and 2024 were retrospectively analyzed.

Ten patients (eight men and two women) with a median age of 54 years and recurrent stage T2-T4N0-N1 disease were included. The median radiation dose before BNCT was 70 (range: 70-124) Gy. For the initial BNCT session, the median average tumor dose was 16.4 (range: 11.7-25.1) Gy-Eq delivered in a single fraction. Two patients underwent a second BNCT session for residual or recurrent disease at 3 and 12 months after the first, respectively. The median follow-up period was 10.7 (range: 2.2-50.9) months. Overall, one complete response and one partial response were observed after one or two BNCT sessions among eight evaluable cases. The most common acute toxicities were low-grade mucositis and dermatitis. No cases of carotid blowout syndrome were reported. Temporal lobe necrosis occurred in one patient who received two BNCT sessions. The one-year overall survival rate was 44.4%, and the one-year progression-free survival rate was 33%. One patient survived for more than 4 years.

In this small cohort of patients with recurrent NPC, compassionate BNCT with moderate doses yielded a 25% response rate and one long-term survivor (4 years). Protocol modifications involving adjusted dose-fractionation schedules and combination with other treatment modalities in future prospective trials may improve the outcomes for recurrent NPC.