Clinical Results and Prognostic Factors in BNCT 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

Abstract

PurposeRecurrent head and neck cancer presents a therapeutic challenge due to cumulative toxicity from initial radiation therapy, limiting re-irradiation 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. Materials and MethodsThis retrospective analysis investigated the initial 47 patients treated with BNCT between May 2020 and February 2021 in Japan. All patients had received radiotherapy with a median dose of 70 Gy (range, 44–176) prior to BNCT. Median tumor size was 11 cm3 (range, 1–117 cm3), with 23% of tumors larger than 30 cm3, 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, 18F-FBPA-PET was performed within 1 week before BNCT, tumor to blood 10B ratio was 3.5 (range, 2.0–8.7). ResultsEfficacy 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 impact on achieving complete response. ConclusionsThis 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.