Department of Radiation Oncology, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, Cancer Hospital affiliate to School of Medicine, University of Electronic Science and Technology of China, Radiation Oncology Key Laboratory of Sichuan Province, Chengdu, China.
School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.
Radiother Oncol. 2022 Jul;172:10-17. doi: 10.1016/j.radonc.2022.04.026. Epub 2022 Apr 29.
To analyze the distribution pattern of lymph nodes (LNs) metastasis of level Ib in nasopharyngeal cancer (NPC) and propose shrinkage of clinical target volume (CTV) boundaries to avoid unnecessary radiation for some space with very low-risk of involvement.
Pretreatment images of pathologically proven NPC patients were reviewed and those with positive level Ib LN metastasis was enrolled. The geometric center of each level Ib LN in the neck was marked on a template CT. The spatial relationship of nodes with key structures in level Ib was analyzed. Modified level Ib CTV according to the 2013 International CTV consensus was proposed based on the LN distribution pattern. A PlanIQ Feasibility DVH module was implemented to evaluate the feasibility analysis of the best possible sparing of organs at risk (OAR) with modified Ib CTV.
A total of 1518 NPC patients were reviewed and 54 with positive level Ib nodes were enrolled. Four sub-level anatomical regions were defined within the gross area of level Ib. Of 106 positive nodes identified, none, one, 88, and 17 were found in the intraglandular (IG), medial mandibular (MM), supra perivascular (SP), and infra perivascular (IP) sub-level, respectively. This study proposes sparing the IG and MM sub-level and including the area within a specified distance from the submandibular gland (11 mm for SP, 17 mm for IP) for CTV coverage. Compared with planning based on CTV-consensus, planning based on CTV-proposed results in a significantly reduced CTV volume, and mean dose (D) of both the ipsilateral SMG and bilateral SLG.
Based on detailed analysis of the relationship between positive node distribution and several important anatomical structures, modified level Ib CTV for prophylactic irradiation was proposed to reduce the dose of OAR irradiation.
分析鼻咽癌（NPC）Ib 区淋巴结（LNs）转移的分布模式，提出缩小临床靶区（CTV）边界，以避免对某些涉及风险极低的空间进行不必要的照射。
回顾经病理证实的 NPC 患者的治疗前图像，纳入 Ib 区阳性淋巴结转移的患者。在模板 CT 上标记颈部每个 Ib 区淋巴结的几何中心。分析 Ib 区淋巴结与 Ib 区内关键结构的空间关系。根据 2013 年国际 CTV 共识，提出基于 LN 分布模式的改良 Ib 区 CTV。使用 PlanIQ Feasibility DVH 模块评估改良 Ib CTV 对最佳保护危及器官（OAR）的可行性分析。
共回顾了 1518 例 NPC 患者，纳入了 54 例 Ib 区阳性淋巴结的患者。在 Ib 区的大体区域内定义了四个亚解剖区域。在 106 个阳性淋巴结中，分别有 0、1、88 和 17 个位于腺内（IG）、下颌内侧（MM）、血管周围上（SP）和血管周围下（IP）亚区。本研究提出保留 IG 和 MM 亚区，并包括距下颌下腺特定距离内的区域（SP 为 11mm，IP 为 17mm）作为 CTV 覆盖范围。与基于 CTV 共识的计划相比，基于 CTV 建议的计划可显著降低 CTV 体积和同侧 SMG 以及双侧 SLG 的平均剂量（D）。
基于阳性淋巴结分布与几个重要解剖结构之间关系的详细分析，提出了改良的 Ib 区预防性照射 CTV，以减少 OAR 照射剂量。
