Prospective observational study of carbon‐ion radiotherapy for non‐squamous cell carcinoma of the head and neck

To evaluate the efficacy and safety of carbon‐ion radiotherapy for non‐squamous cell carcinoma of the head and neck, 35 patients were enrolled in this prospective study. The primary end‐point was the 3‐year local control rate, and the secondary end‐points included the 3‐year overall survival rate and adverse events. Acute and late adverse events were evaluated according to the Common Terminology Criteria for Adverse Events, version 4.0. The median follow‐up time for all patients was 39 months. Thirty‐two and three patients received 64.0 Gy (relative biological effectiveness) and 57.6 Gy (relative biological effectiveness) in 16 fractions, respectively. Adenoid cystic carcinoma was dominant (60%). Four patients had local recurrence and five patients died. The 3‐year local control and overall survival rates were 93% and 88%, respectively. Acute grade 2–3 radiation mucositis (65%) and dermatitis (31%) was common, which improved immediately with conservative therapy. Late mucositis of grade 2, grade 3, and grade 4 were observed in 11, one, and no patients, respectively. There were no adverse events of grade 5. Carbon‐ion radiotherapy achieved excellent local control and overall survival rates for non‐squamous cell carcinoma. However, the late mucosal adverse events were not rare, and meticulous treatment planning is required. Trial registration no. UMIN000007886.