Boron neutron capture therapy for unresectable residual external auditory canal carcinoma

Boron neutron capture therapy (BNCT) is a radiation therapy that utilizes the alpha rays produced by the thermal neutron capture reaction of boron nuclei. With BNCT, only unresectable head and neck cancer (HNC) is currently covered by medical insurance in Japan. Some authors have reported the outcomes of BNCT for HNC, but individual case reports are lacking; therefore, the detailed clinical course of such patients remains poorly understood. Herein, we report a case of BNCT treatment for an unresectable residual lesion of external auditory canal carcinoma. A 59-year-old man was diagnosed with squamous cell carcinoma of the right auditory canal. He underwent right lateral temporal bone resection surgery followed by additional chemoradiotherapy; however, a residual preauricular lesion and an unresectable residual lesion deep in the middle ear were identified 2 months later. BNCT was administered for the middle ear and preauricular lesion. Although the preauricular lesion required an additional surgical excision, the middle ear lesion remained locally controlled at the 3-year follow-up. Grade 3 brain radiation necrosis and skin disorders occurred as late adverse events, however, the patient continued his daily activities without any impairment in his quality of life.