To evaluate the safety and efficacy of carbon-ion radiation therapy (C-ion RT) for locally advanced sinonasal malignant tumors in a multicenter retrospective study (J-CROS 1402 HN). Clinical data were collected for patients who had sinonasal malignant tumors of stage N0-1M0 and received C-ion RT at 4 institutions in Japan between November 2003 and December 2014. Of the 458 patients, 393 had naïve tumors and 65 had recurrent tumors. The tumors were located in the nasal cavity (n = 263), maxillary sinus (n = 109), ethmoid sinus (n = 71), and other locations (n = 15). The histologic types were mucosal melanoma (n = 221, 48%), adenoid cystic carcinoma (n = 122, 27%), squamous cell carcinoma (n = 31, 7%), olfactory neuroblastoma (n = 30, 7%), adenocarcinoma (n = 21, 5%), and other types (n = 33, 7%). Of the 458 patients, 300 (66%) had T4 tumors. All patients received definitive C-ion RT. The median follow-up period was 25.2 months for all patients (range, 1.4-132.3 months). The 2-year overall survival and local control rates were 79.6% and 84.1%, respectively. As analyzed according to histology, the 2-year overall survival rate was 68.0% for mucosal melanoma, 96.8% for adenoid cystic carcinoma, 70.0% for squamous cell carcinoma, 96.7% for olfactory neuroblastoma, and 89.7% for adenocarcinoma. Regarding late toxicities, 17% of patients developed grade 3 and 4 toxicities, of which visual impairment was the most common. The results of our multicenter study have demonstrated that C-ion RT can provide excellent clinical outcomes with acceptable late toxicities in patients who have locally advanced sinonasal malignant tumors.

Proton beam therapy (PBT) is a potential new alternative to treatment with photon radiotherapy that may reduce the risk of late toxicity and secondary cancer, especially for pediatric tumors. The goal of this study was to evaluate the long‐term benefits of PBT in cancer survivors. A retrospective observational study of pediatric patients who received PBT was performed at four institutions in Japan. Of 343 patients, 62 were followed up for 5 or more years. These patients included 40 males and 22 females, and had a median age of 10 years (range: 0–19 years) at the time of treatment. The irradiation dose ranged from 10.8 to 81.2 GyE (median: 50.4 GyE). The median follow‐up period was 8.1 years (5.0–31.2 years). The 5‐, 10‐ and 20‐year rates for grade 2 or higher late toxicities were 18%, 35% and 45%, respectively, and those for grade 3 or higher late toxicities were 6%, 17% and 17% respectively. Univariate analysis showed that the irradiated site (head and neck, brain) was significantly associated with late toxicities. No malignant secondary tumors occurred within the irradiated field. The 10‐ and 20‐year cumulative rates for all secondary tumors, malignant secondary tumors, and malignant nonhematologic secondary tumors were 8% and 16%, 5% and 13%, and 3% and 11%, respectively. Our data indicate that PBT has the potential to reduce the risk of late mortality and secondary malignancy. Longer follow‐up is needed to confirm the benefits of PBT for pediatric tumors.