3740 - Two Years of Clinical Experience with Accelerator-Based Boron Neutron Capture Therapy for Head and Neck Cancer

S. Takeno^1,2, Y. Yoshino^1,2, T. Aihara^2,3, M. Higashino³, Y. Kanai^2,4, N. Hu^2,5, R. Kakino², R. Kawata³, K. Nihei^1,2, and K. Ono^2,4; ¹Department of Radiation Oncology, Osaka Medical and Pharmaceutical University, Osaka, Japan, ²Kansai BNCT Medical Center, Osaka Medical and Pharmaceutical University, Osaka, Japan, ³Department of Otorhinolaryngology - Head and Neck Surgery, Osaka Medical and Pharmaceutical University, Osaka, Japan, ⁴BNCT Joint Clinical Institute, Osaka Medical and Pharmaceutical University, Osaka, Japan, ⁵Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan

Purpose/Objective(s): Boron neutron capture therapy (BNCT) is a treatment in which tumor cells are irradiated with thermal neutrons after they have absorbed boron drug. The boron neutron capture reaction occurs in the cells that have taken up the boron drug and selectively destroys the cells, thereby maximizing the effect on the tumor cells while minimizing damage to normal tissue. Since June 2020, accelerator-based BNCT has been a healthcare service covered by health insurance in Japan to treat unresectable locally advanced or locally recurrent head and neck cancers. However, its role in the standard of treatment of surgery, radiation therapy, and chemotherapy is not yet clear. Therefore, we aimed to evaluate the clinical outcomes of BNCT as a health insurance treatment and explore its role among the standard treatment modalities for head and neck cancers. Materials/

Methods: We retrospectively analyzed data of patients treated with BNCT at Kansai BNCT Medical Center, Osaka Medical and Pharmaceutical University, between June 2020 and May 2022. Post-treatment follow-up was performed at our institution whenever possible; however, if the patient lived too far away, it was performed at the referring institution. The observation period lasted until February 2024. We evaluated the best overall response rate according to the Response Evaluation Criteria in Solid Tumors version 1.1, and adverse events according to the Common Terminology Criteria for Adverse Events, version 5.0. In addition, we performed a survival analysis and examined the factors that contributed to the treatment outcomes.

Results: Sixty-nine patients (72 treatments) were included in the study, with a median observation follow-up of 17 months. The best overall response rate was 80.5%, and the 1-year locoregional control, progression-free survival, and overall survival rates were 57.6% (95% confidence interval [CI]: 44.4–68.7%), 42.8% (95% CI: 30.7–54.3%), and 76.0% (95% CI: 63.3–84.8%), respectively. There was a trend toward longer locoregional control in patients with earlier TNM staging. Regarding late adverse events (Grade 3 or higher), skin ulceration, pharyngeal fistula, central nervous system necrosis, esophageal perforation, and laryngeal necrosis were observed in 3, 2, 2, 1, and 1 cases, respectively. The case of esophageal perforation resulted in a grade 5 perforation due to carotid rupture.

Conclusion: BNCT may be an effective treatment option for unresectable locally advanced or locally recurrent head and neck cancer with no other definitive therapies. When definitive surgery or radiation therapy are not feasible, BNCT may be considered in the early stages of the disease. Although the conditions of its indication should be carefully considered, the risk is considered acceptable given the tumor status and limited alternative treatment options.