HighlightsHigh LET and high RBE of carbon ion made it a promising tool for treating pancreatic cancers.Dose averaged LET minimum within the GTV is significantly associated with local control.Outcome of CIRT in pancreatic cancers can be improved by modulating dose averaged LET within the GTV.

Background and purpose: Locoregional recurrence after carbon-ion radiotherapy (CIRT) for primary head and neck malignancies, such as malignant mucosal melanoma, adenoid cystic carcinoma, and sarcoma, occurs occasionally. However, the treatment options are limited. We report on the toxicity and efficacy of re-irradiation using carbon ions for recurrent head and neck malignancies after CIRT. Materials and methods: Data of 48 patients with recurrent head and neck malignancies treated with reirradiation with CIRT at our institution (2007-2016) were retrospectively analyzed. Twenty-one patients (43.8%) had malignant mucosal melanoma, 17 (35.4%) had adenoid cystic carcinoma, six (12.5%) had bone and soft tissue sarcomas, and four patients (8.3%) had other disease types. Tumor recurrences at reirradiation were located in the paranasal cavity (n = 18, 37.5%), nasal cavity (n = 9, 18.8%), nasopharynx (n = 4, 8.3%), orbit (n = 3, 6.3%), cavernous sinus (n = 3, 6.3%), and at other sites (n = 11, 22.9%). The median dose of initial CIRT and that at re-irradiation were 57.6 Gy and 54.0 Gy (relative biological effectiveness [RBE]), respectively. None of the patients received concurrent chemotherapy. Results: The median follow-up period after re-irradiation was 27.1 months. Five patients (10.4%) developed Grade 3 acute toxicities and 18 (37.5%) developed Grade 3 late toxicities, including Grade 5 central nervous system necrosis in one patient. The 2-year local control, locoregional control, progression-free survival, and overall survival rates were 40.5, 33.5%, 29.4%, and 59.6%, respectively. Conclusion: Re-irradiation using carbon ions may be a reasonable treatment option with tolerable toxicity for patients with recurrent head and neck malignancies after CIRT.

Background We evaluated the long‐term efficacy and safety of carbon‐ion radiotherapy (C‐ion RT) for skull base chordoma, a rare neoplasm. Methods Thirty‐four patients with skull base chordoma who were treated with C‐ion RT were prospectively enrolled and analyzed retrospectively. C‐ion RT was delivered with 60.8 Gy (relative biological effectiveness [RBE]) in 16 fractions at four fractions per week. Results The median follow‐up period was 108 months. The 5‐ and 9‐year local control rates were 76.9% and 69.2%, respectively. The 5‐ and 9‐year overall survival rates were 93.5% and 77.4%, respectively. Regarding grade 3 or more severe late reactions, one patient developed a grade 3 mucosal ulcer, two developed grade 4 ipsilateral optic nerve injuries, and one developed a grade 5 mucosal ulcer at 9 years and 3 months after C‐ion RT. Conclusion C‐ion RT with 60.8 Gy (RBE)/16 fractions is a promising treatment option for inoperable skull base chordoma.

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