Laboratory of Radiation Physics, Odense University Hospital, Denmark; Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
Department of Oncology, Odense University Hospital, Denmark.
Radiother Oncol. 2018 Jan;126(1):43-47. doi: 10.1016/j.radonc.2017.09.019. Epub 2017 Oct 4.
Defining margins around the Gross Tumour Volume (GTV) to create a Clinical Target Volume (CTV) for head and neck cancer radiotherapy has traditionally been based on presumed knowledge of anatomical routes of spread. However, using a concentric geometric expansion around the GTV may be more reproducible. The purpose of this study was to analyse the inter-observer consistency of geometric CTV delineation with adaptation for anatomical boundaries versus anatomically defined CTVs.
Radiation oncologists at four Danish cancer centres delineated high, intermediate and elective dose CTVs (CTV1, CTV2 and CTV3, respectively) in a patient-case template (stage IV squamous cell carcinoma of the oropharynx), first using mainly anatomical margins (original standard) and then using concentric geometric expansion (new standard). Each centre made a dummy-run radiotherapy plan based on the delineated CTVs. The difference between the CTV contours and the radiotherapy plans was evaluated across the centres.
Anatomy-based contours were significantly more heterogenous and showed larger volume differences between centres than geometric margins. Dice similarity coefficient increased by 0.29 and mean surface distance decreased by 4mm for CTV1. Use of consistent CTV volumes resulted in more consistent irradiated volumes between centres.
Introduction of geometric margins resulted in more uniform CTV1 and CTV2 delineation. Geometric CTV expansion was easier, left less room for misinterpretation, and resulted in more uniform treatment plans with similar irradiated high and intermediate dose volumes across all centres.
为头颈部癌症放射治疗的肿瘤靶区（CTV）定义围绕大体肿瘤靶区（GTV）的边缘，传统上是基于对解剖扩散途径的假定知识。然而，使用 GTV 周围的同心几何扩展可能更具可重复性。本研究的目的是分析几何 CTV 勾画的观察者间一致性，以及适应解剖边界与解剖定义的 CTV 的一致性。
丹麦四个癌症中心的放射肿瘤学家在一个患者模板（口咽期 IV 期鳞状细胞癌）中勾画高、中、选择性剂量 CTV（CTV1、CTV2 和 CTV3），首先主要使用解剖边界（原始标准），然后使用同心几何扩展（新标准）。每个中心根据勾画的 CTV 进行模拟放疗计划。在各中心之间评估 CTV 轮廓和放疗计划之间的差异。
基于解剖的轮廓明显更不均匀，且各中心之间的体积差异也更大。对于 CTV1，Dice 相似性系数增加了 0.29，平均表面距离减少了 4mm。使用一致的 CTV 体积导致各中心之间的照射体积更一致。
引入几何边界导致 CTV1 和 CTV2 的勾画更均匀。几何 CTV 扩展更简单，减少了误解的空间，并且在所有中心都产生了更均匀的治疗计划，具有相似的高剂量和中剂量照射体积。
