BACKGROUND Oronasal fistulae (ONF) are one of the rare but serious complications of conventional photon radiotherapy. This study aimed to identify the risk factors for the development of ONF after carbon-ion radiotherapy (C-ion RT). MATERIALS AND METHODS The data of 62 cases of sinonasal and oral cavity cancers treated with C-ion RT and followed-up in excess of 5 years were retrospectively reviewed. The correlation between the clinical and dosimetric parameters and the development of ONF was analysed. RESULTS A total of 80.6% cases had sinonasal malignancies, and most tumours had advanced T stages (96.8%). Maxillary invasion was observed in 16 cases (25.8%), and malignant melanoma was the most common histology (46.8 %). All the cases received a dose of between 57.6 Gy (RBE) and 64 Gy (RBE) in 16 fractions over 4 weeks. At a median follow up of 88.8 months, 23 cases (37.1%) developed small localised ONF; however, none were of grade III severity. On separate multivariate analyses of clinical parameters in the entire cohort and in cases without maxillary invasion, the number of teeth irradiated with more than 50 Gy (RBE) was found to be the common significant independent risk factor for development of ONF. CONCLUSION The number of teeth irradiated with more than 50 Gy (RBE) is a significant independent risk factor for the development of ONF, which is a late complication of C-ion RT delivered in 16 fractions.

中文翻译：

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评估与头颈癌碳离子放疗后晚期并发症口鼻瘘发生相关的危险因素

背景口鼻瘘（ONF）是常规光子放射治疗的罕见但严重的并发症之一。本研究旨在确定碳离子放疗 (C-ion RT) 后发生 ONF 的危险因素。材料与方法 回顾性分析62例经C-ion RT治疗并随访5年以上的鼻窦癌和口腔癌的资料。分析了临床和剂量学参数与ONF发展之间的相关性。结果 80.6%的病例为鼻腔鼻腔恶性肿瘤，大多数肿瘤为晚期T分期（96.8%）。在 16 例（25.8%）中观察到上颌浸润，恶性黑色素瘤是最常见的组织学类型（46.8%）。所有病例在 4 周内分 16 次接受了 57.6 Gy (RBE) 至 64 Gy (RBE) 的剂量。中位随访 88 次。8个月，23例（37.1%）发生小局部ONF；然而，没有一个严重程度为 III 级。在对整个队列和没有上颌骨侵犯的情况下的临床参数进行单独的多变量分析时，发现照射超过 50 Gy (RBE) 的牙齿数量是发生 ONF 的常见显着独立危险因素。结论 超过 50 Gy (RBE) 照射的牙齿数量是发生 ONF 的重要独立危险因素，ONF 是分 16 次进行 C 离子放疗的晚期并发症。发现接受超过 50 Gy (RBE) 照射的牙齿数量是发生 ONF 的常见显着独立危险因素。结论 超过 50 Gy (RBE) 照射的牙齿数量是发生 ONF 的重要独立危险因素，ONF 是分 16 次进行 C 离子放疗的晚期并发症。发现接受超过 50 Gy (RBE) 照射的牙齿数量是发生 ONF 的常见显着独立危险因素。结论 超过 50 Gy (RBE) 照射的牙齿数量是发生 ONF 的重要独立危险因素，ONF 是分 16 次进行 C 离子放疗的晚期并发症。