Clinical Results and Prognostic Factors in Boron Neutron Capture Therapy for Recurrent Squamous Cell Carcinoma of the Head and Neck Under the Japan National Health Insurance System: A Retrospective Study of the Initial 47 Patients.

Purpose: Recurrent head and neck cancer presents a therapeutic challenge because of cumulative toxicity from initial radiation therapy, limiting reirradiation options. Boron neutron capture therapy (BNCT) offers a promising alternative, selectively delivering a radical dose to tumors while sparing adjacent normal tissue. This study investigates the initial clinical outcomes and prognostic factors associated with BNCT for recurrent squamous cell carcinoma of the head and neck.
Methods and Materials: This retrospective analysis investigated the initial 47 patients treated with BNCT between May 2020 and February 2021 in Japan. All patients had received radiation therapy with a median dose of 70 Gy (range, 44-176) before BNCT. Median tumor size was 11 cm ³ (range, 1-117 cm ³ ), with 23% of tumors larger than 30 cm ³ , and 87% of patients had prior systemic therapy. The most common prescribed dose to the pharyngeal mucosa was 15 Gy-Eq (36%), followed by 18 Gy-Eq (34%). The minimum dose given to tumor was 27.4 Gy-Eq (range, 13.3-45.2). In 23 patients, ¹⁸ F-fluoro-borono-phenylalanine positron emission tomography was performed within 1 week before BNCT, and the tumor-to-blood ¹⁰ B ratio was 3.5 (range, 2.0-8.7).
Results: Efficacy analysis revealed a 51% complete response rate and a 74% overall response rate. Disease-free survival rates at 1 and 2 years were 34.6% and 26.6%, respectively. Overall survival rates at 1 and 2 years were 86.1% and 66.5%, respectively. Multivariate analysis revealed that, among the patient characteristics, whether the lesion was mucosal had a significant effect on achieving complete response.
Conclusions: This study provided valuable insights into the early integration of BNCT into routine clinical practice, highlighting its efficacy and safety. Technical improvements are needed to ensure precise dose administration. Ongoing prospective studies, such as the phase II REBIVAL study, will further elucidate the role of BNCT in recurrent head and neck cancer.
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