一种用于患有咽旁间隙侵犯及Ⅱa级颈淋巴结受累的鼻咽癌患者容积调强弧形治疗中剂量优化的腮腺分割勾画方法。
A split-parotid delineation approach for dose optimization in volumetric modulated arc therapy for nasopharyngeal carcinoma patients with parapharyngeal space invasion and level IIa cervical lymph node involvements.
作者信息
Xiao Wei, Lin Zhixiong, Zhang Wuzhe, Li Mei, Wu Vincent W C
机构信息
1 Cancer Hospital, Shantou University Medical College, Shantou, Guangdong, China.
2 Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR.
出版信息
Br J Radiol. 2016;89(1060):20150635. doi: 10.1259/bjr.20150635. Epub 2016 Feb 3.
OBJECTIVE
This study evaluated the potential benefit of a split-parotid delineation approach on the parotid gland in the treatment planning of patients with nasopharyngeal carcinoma (NPC).
METHODS
50 patients with NPC with parapharyngeal space (PPS) and/or level IIa cervical node involvements were divided into three groups: PPS only, level IIa cervical node only and both. Two volumetric-modulated arc therapy plans were computed. The first plan (control) was generated based on the routine treatment-planning protocol, while the second plan (test) was computed with the split-parotid delineation approach, in which a line through the anterolateral margin of the retromandibular vein was created that divided the parotid gland into anterolateral and posteromedial subsegments. For the test plan, the anterolateral subsegment was prescribed, with a dose constraint of 25 Gy in the plan optimization. Dosimetric data of the parotid gland, target volumes and selected organs at risk (OARs) were compared between the control and test plans.
RESULTS
The mean dose to the anterolateral subsegment of the parotid gland in all three groups was kept below 25 Gy. The test plan demonstrated significantly lower mean parotid dose than the control plan in the entire gland and the anterolateral subsegment in all three groups. The difference was the greatest in Group 3.
CONCLUSION
The split-parotid delineation approach significantly lowered the mean dose to the anterolateral subsegment and overall gland without greatly compromising the doses to target volumes and other OARs. The effect was more obvious for both PPS and level IIa cervical node involvements than for either of them alone.
ADVANCES IN KNOWLEDGE
It is the first article based on the assumption that parotid gland stem cells are situated at the anterolateral segment of the gland, and applied the split-parotid delineation approach to the parotid gland in the treatment planning of patients with NPC with PPS and level IIa cervical node involvements, so that the function of the post-radiotherapy parotid gland might be better preserved.
目的
本研究评估了在鼻咽癌（NPC）患者治疗计划中，腮腺分割勾画方法对腮腺的潜在益处。
方法
50例伴有咽旁间隙（PPS）和/或Ⅱa级颈淋巴结受累的NPC患者被分为三组：仅PPS受累组、仅Ⅱa级颈淋巴结受累组和两者均受累组。计算了两个容积调强弧形治疗计划。第一个计划（对照）基于常规治疗计划方案生成，而第二个计划（测试）采用腮腺分割勾画方法计算，即在颌下后静脉前外侧缘作一条线，将腮腺分为前外侧和后内侧亚段。对于测试计划，在计划优化时规定前外侧亚段的剂量限制为25 Gy。比较对照计划和测试计划中腮腺、靶区体积和选定危及器官（OAR）的剂量学数据。
结果
所有三组腮腺前外侧亚段的平均剂量均保持在25 Gy以下。测试计划显示，在所有三组中，整个腮腺和前外侧亚段的平均腮腺剂量均显著低于对照计划。第3组的差异最大。
结论
腮腺分割勾画方法显著降低了前外侧亚段和整个腮腺的平均剂量，同时对靶区体积和其他OAR的剂量没有造成太大影响。对于PPS和Ⅱa级颈淋巴结均受累的情况，其效果比单独受累更为明显。
知识进展
这是第一篇基于腮腺干细胞位于腺体前外侧段这一假设的文章，并将腮腺分割勾画方法应用于伴有PPS和Ⅱa级颈淋巴结受累的NPC患者的治疗计划中，从而可能更好地保留放疗后腮腺的功能。
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