A retrospective multicenter study was conducted to assess the clinical outcomes of carbon-ion radiotherapy for head and neck malignancies(Japan Carbon-Ion Radiation Oncology Study Group[J-CROS] study: 1402 HN). Patients with head and neck malignancies with N0-1M0 status who were treated with carbon-ion RT at four institutions in Japan between November 2003 and December 2014 were analyzed retrospectively. Nine hundred and eight patients were enrolled. Primary sites included the sinonasal cavity in 458 patients(50.4%), choroid in 119(13.1%), oral cavity in 83(9.1%), major salivary gland in 69(7.6%), orbit in 48(5.3%), nasopharynx in 46 (5.1%), and the others in 85(9.4%). Twenty-eight patients(3.1%) had T1 tumors, 59(6.5%) had T2 tumors, 295(32.5%) had T3 tumors, 509(56.1%) had T4 tumors, and 17(1.8%) had unclassified tumors. The disease histologic type was as follows: 387 patients (42.6%) had malignant melanoma, 289 (31.8%) had adenoid cystic carcinoma, 63 (6.9%) had squamous cell carcinoma, 47 (5.2%) had adenocarcinoma, and 122 (13.4%) had others. The median follow-up duration was 28 months. The 3-year and 5-year local control rates were 81% and 74%, respectively. The 3-year and 5-year overall survival rates were 76% and 64%, respectively. Late toxicities of grade 4 or more were observed in 4.4% of the patients. Carbon-ion radiotherapy is one of the promising treatment options for locally advanced head and neck malignancies, particularly radio-resistant tumors such as non-squamous cell carcinomas.
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