Feasibility of carbon‐ion radiotherapy for oral non‐squamous cell carcinomas

BACKGROUND: This study evaluated carbon‐ion radiotherapy (C‐ion RT) for oral non‐squamous cell carcinomas (non‐SCC). METHODS: We retrospectively obtained data from 74 patients who underwent C‐ion RT for oral malignancies between April 1997 and March 2016. The C‐ion RT was administered in 16 fractions at a total dose of 57.6 or 64.0 Gy (relative biological effectiveness). RESULTS: Forty‐three patients had salivary gland carcinomas, 29 patients had mucosal melanoma, and 2 patients had other types of pathologies. The tumors were classified as T1‐T3 (24 cases), T4a (21 cases), or T4b (29 cases). The median follow‐up was 49 months. The 5‐year rates were 78.8% for local control, 36.2% for progression‐free survival, and 58.3% for overall survival. Although 10 patients developed grade 3 osteoradionecrosis after C‐ion RT, all patients maintained their mastication and deglutition functions after sequestrectomy and prosthesis placement. CONCLUSION: C‐ion RT was effective for oral non‐SCC and had acceptable toxicities.