Treatment outcome of ion beam therapy in eight patients with head and neck cancers.

Ion beam therapy has enabled us to treat formerly untreatable malignant tumors. The aim of the present study was to investigate the long-term follow-up course of patients with head and neck cancers who received ion beam therapy. The subjects were 8 patients (3 men and 5 women aged 43-78 years) with head and neck cancers who visited our department from 2006 to 2015 and received ion beam therapy. Six patients received carbon ion beam therapy, and the other two patients received proton beam therapy. The medical records of the patients were retrospectively analyzed. The primary site was the nasal and paranasal sinuses in six cases, nasopharynx in one case, and external auditory canal in one case. The histological type was olfactory neuroblastoma, malignant melanoma, and adenoid cystic carcinoma in two cases each, and chondrosarcoma and squamous cell carcinoma in one case each. The exposure dose ranged from 64 to 70.4 GyE. The average follow-up period was 42.0 months. Early adverse events were generally mild, and complete therapeutic response was obtained in all cases. However, five patients developed severe late complications including craniospinal dissemination, osteoradionecrosis of the maxilla and skull base, brain necrosis, and loss of eyesight. Three patients died of distant metastasis, local recurrence and/or brain necrosis within 2 years, and four patients have been surviving with distant metastasis or severe late complications. Ion beam therapy exhibits outstanding antitumor effects, but the severe late complications of the therapy must also be recognized.