Successful salvage surgery for BNCT-induced hypopharyngeal fistula with carotid artery protection using a pedicled pectoralis major muscle flap.

Boron Neutron Capture Therapy (BNCT) is an emerging treatment for locally advanced or recurrent head and neck cancer, but severe late complications, including pharyngeal fistula and carotid blowout, may occur. We report a 71-year-old man with a hypopharyngeal fistula 2 mm from the common carotid artery after BNCT for hypopharyngeal squamous cell carcinoma. Progressive necrosis posed a high risk of carotid exposure and rupture, prompting urgent salvage surgery. After debridement, a 15 × 20 mm full-thickness pharyngeal wall defect remained adjacent to the carotid artery. A pedicled pectoralis major muscle flap was wrapped around the carotid artery for circumferential protection, and the mucosal edge was sutured to the muscle body to close the fistula. The exposed muscle surface subsequently epithelialized. Oral intake was resumed after swallowing rehabilitation, with no fistula recurrence, surgical-site complications, or tumor recurrence by postoperative month 9. In carefully selected cases with a localized defect suitable for secondary epithelialization and high risk of carotid blowout, a pedicled muscle flap may represent a useful reconstructive option for carotid protection and fistula closure.