Evaluation of the safety and efficacy of carbon ion radiotherapy for locally advanced adenoid cystic carcinoma of the tongue base

Background. Most cases of adenoid cystic carcinoma (ACC) of the tongue base are radioresistant, and are diagnosed in the advanced stage. Therefore, we evaluated the safety and efficacy of carbon ion radiotherapy (C-ion RT) for locally advanced ACC of the tongue base. Methods. Eighteen patients with ACC of the tongue base were treated with C-ion RT between May 2002 and April 2014. Seventeen patients had T4a disease and 1 patient had T2 disease before C-ion RT. Results. The median follow-up period was 57 months (range, 10-132 months). The 5-year local control rate was 92%. The 5-year overall survival (OS) and disease-free survival (DFS) rates were 72% and 44%, respectively. Regarding late reactions, 2 patients developed grade 3 mandible osteoradionecrosis, and 1 had grade 3 hemorrhage of the tongue base. Conclusion. C-ion RT was effective with acceptable toxicities for locally advanced ACC of the tongue base. (C) 2016 Wiley Periodicals, Inc.