Boron neutron capture therapy as a larynx-preserving treatment for locally recurrent laryngeal carcinoma after conventional radiation therapy: A preliminary report

Objective: Laryngeal preservation and a radical cure are the treatment goals for laryngeal carcinoma, and larynx-preserving therapy is generally preferred for early-stage laryngeal carcinoma. When laryngeal carcinoma recurs locally, patients are often forced to undergo total laryngectomy, resulting in loss of vocal function. However, many patients with laryngeal carcinoma who have residual or recurrent disease after radiotherapy wish to preserve their voice. The purpose of this study was to investigate the possibility of using BNCT as a larynx-preserving treatment for residual or recurrent laryngeal carcinomas following radical irradiation.

Patients and methods: This study included 15 patients who underwent BNCT for residual or recurrent laryngeal carcinoma after radical laryngeal carcinoma irradiation. The number of treatment sessions for all patients was one irradiation. Before BNCT, the recurrent laryngeal carcinoma stage was rT1aN0, rT2N0, rT2N1, rT3N0, rT3N1, and rT4aN0 in one, six, one, three, one, and three patients, respectively. The median maximum tumor diameter before BNCT was 15 mm (8-22 mm). All patients underwent a tracheostomy before BNCT to mitigate the risk of upper airway stenosis due to laryngeal edema after BNCT. Treatment efficacy was evaluated retrospectively using monthly laryngoscopy after BNCT and contrast-enhanced CT scans at 3 months. The safety of treatment was evaluated based on examination findings and interviews with patients.

Results: The median hospital stay after BNCT was 2 days (1-6). The response rate at three months after BNCT in 15 patients with locally recurrent laryngeal carcinoma was 93.3 %, and the CR rate was 73.3 %. The most frequent adverse event associated with BNCT was laryngeal edema, which occurred in nine patients the day after BNCT. The average course of laryngeal edema peaked on the second day after BNCT and almost recovered after 1 week in all patients. One patient had bilateral vocal fold movement disorders. None had dyspnea because of prophylactic tracheostomy. No grade four or higher adverse events occurred. Other grade 2 adverse events included pharyngeal mucositis, diarrhea, and sore throat. Three months after BNCT, tracheostomy tubes were removed in nine patients, retinal cannulas were placed in three patients, and voice cannulas were placed in three patients.

Conclusions: BNCT for locally recurrent laryngeal carcinoma can safely deliver radical irradiation to tumor tissues, even in patients undergoing radical irradiation. BNCT has shown antitumor effects against recurrent laryngeal carcinoma. However, further long-term observations of the treatment outcomes are required.