Target coverage and local recurrences after radiotherapy for sinonasal cancer in Denmark 2008–2015. A DAHANCA study

The study aimed to investigate the pattern of failure and describe compromises in the definition and coverage of the target for patients treated with curatively intended radiotherapy (RT) for sinonasal cancer (SNC). Patients treated with curatively intended RT in 2008–2015 in Denmark for SNC were eligible for the retrospective cohort study. Information regarding diagnosis and treatment was retrieved from the national database of the Danish Head and Neck Cancer Group (DAHANCA). Imaging from the diagnosis of recurrences was collected, and the point of origin (PO) of the recurrent tumour was estimated. All treatment plans were collected and reviewed with the focus on target coverage, manual modifications of target volumes, and dose to organs at risk (OARs) above defined constraints. A total of 184 patients were included in the analysis, and 76 (41%) relapsed. The majority of recurrences involved T-site (76%). Recurrence imaging of 39 patients was evaluated, and PO was established. Twenty-nine POs (74%) were located within the CTV, and the minimum dose to the PO was median 64.1 Gy (3.1–70.7). The criteria for target coverage (V95%) was not met in 89/184 (48%) of the CTV and 131/184 (71%) of the PTV. A total of 24% of CTVs had been manually modified to spare OARs of high-dose irradiation. No difference in target volume modifications was observed between patients who suffered recurrence and patients with lasting remission. The majority of relapses after radical treatment of SNC were located in the T-site (the primary tumour site). Multiple compromises with regards to target coverage and tolerance levels for OARs in the sinonasal region, as defined from RT guidelines, were taken. No common practice in this respect could be derived from the study.本研究旨在探讨鼻窦癌（sinonasal cancer, SNC）患者接受根治性放疗（radiotherapy, RT）后的复发失败模式，并阐明靶区定义与覆盖范围存在的未达标准情况。2008年至2015年在丹麦接受根治性放疗的鼻窦癌患者，符合本回顾性队列研究的入组标准。本研究相关诊断与治疗信息均从丹麦头颈癌协作组（Danish Head and Neck Cancer Group, DAHANCA）的国家数据库中调取。收集复发诊断相关影像学资料，并估算复发肿瘤起源位点（point of origin, PO）。收集所有治疗计划并进行回顾审查，重点关注靶区覆盖情况、靶区体积的手动调整，以及超过预设剂量限制的危及器官（organs at risk, OARs）受照剂量。本研究共纳入184例患者进行分析，其中76例（41%）出现复发。大部分复发部位位于原发肿瘤位点（T-site，76%）。对39例患者的复发影像学资料进行评估并明确其复发肿瘤起源位点，其中29处（74%）起源位点位于临床靶区（clinical target volume, CTV）内，该位点的最低受照剂量中位数为64.1 Gy（范围3.1~70.7 Gy）。89例（48%）临床靶区、131例（71%）计划靶区（planning target volume, PTV）未达到靶区覆盖标准（95%处方剂量覆盖体积，V95%）。总计24%的临床靶区曾被手动调整，以避免危及器官受到高剂量照射。复发患者与持续缓解患者之间，靶区体积调整的比例无显著差异。鼻窦癌根治性治疗后的大部分复发均位于原发肿瘤位点。按照放疗指南的要求，在靶区覆盖与鼻窦区域危及器官耐受剂量限值方面，存在多处未达标准的权衡妥协。本研究未发现该领域存在统一的临床实践规范。