Early response and acute adverse effect after particle radiation therapy for adenoid cystic carcinoma of the head and neck

Objective To study the early response and acute/subacute adverse effects after particle radiation therapy for adenoid cystic carcinoma (ACC) of the head and neck. Methods Between May 2015 and March 2016, a total of 8 patients with ACC of the head and neck were treated using proton and/or carbon-ion radiation therapy. Three patients had early stage and 5 had locally advanced disease. Five patients had an R2 and three achieved an R1 resection. Results Seven patients received intensity-modulated proton therapy (IMPT) followed by intensity-modulated carbon-ion therapy (IMCT) boost. One patient received IMPT only. Among the five patients who had an R2 resection, 2/3 patients had partial response (PR)/stable disease (SD) at the end of radiation, 0/3 achieved PR/complete response (CR) at 1-month follow-up, and 1/2 achieved PR/CR at 3-months′ follow-up after the completion of radiation, respectively. Two patients experienced Grade Ⅲ mucositis during radiation therapy. No patient experienced moderate or severe skin reactions. At the time of this analysis, all patients are alive and no patient had disease progression or recurrence. Conclusions The short-term outcomes indicated that particle therapy is safe and potentially efficacious in the management of head and neck ACC. However, longer follow up is needed to assess late toxicities and long-term efficacy. Key words: Head and neck ACC; Proton; Heavy ion; Radiation therapy