Salvage surgery following boron neutron capture therapy in a case of recurrent hypopharyngeal cancer after radiotherapy: Surgical and pathological insights.

Radiotherapy (RT) is a cornerstone management strategy for head and neck cancer (HNC); however, local recurrence often requires salvage surgery, which is associated with an elevated risk of complications, particularly in previously irradiated fields. Boron neutron capture therapy (BNCT) has broadened treatment options; however, the safety and feasibility of salvage surgery after BNCT remain unclear owing to the limited case number. Herein, we describe a rare case of hypopharyngeal squamous cell carcinoma initially treated with RT, followed by BNCT for local recurrence, and ultimately with successful salvage surgery. The patient experienced no significant intraoperative or postoperative complications, and has remained recurrence-free for three years while maintaining adequate activities of daily living. Histopathological examination revealed no abnormal fibrosis exceeding that typically observed following standard RT alone throughout the resected specimen. Instead, edematous changes predominated over fibrotic alterations exclusively within the tumor region, presumed to be most affected by BNCT, accompanied by strong expression of L-type amino acid transporter 1, a potential surrogate marker of BNCT indication, suggesting the tumor-specific therapeutic effect of BNCT. This is the first report of salvage surgery for an organ previously treated with RT and BNCT, which provides valuable clinical and histopathological insights into this condition.