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Abstract：
OBJECTIVE: To recommend a cranial border for level IIb in delineating clinical target volumes (CTV) for nasopharyngeal carcinoma (NPC) patients receiving intensity-modulated radiotherapy and to help reach a consensus on contouring level IIb in CTV.
METHODS: From 2012 to 2016, 331 nonmetastatic NPC patients treated with IMRT were retrospectively enrolled. Based on the AJCC 8th staging system of NPC, there were 15 stage I, 76 stage II, 103 stage III, and 137 stage IV patients. The distribution of cervical lymph nodes in NPC was assessed based on imaging. Comparisons of the safety and parotid dose parameters between patients with and without a reduction in the size of level IIb were conducted using SPSS 25.0 and R 2.14.2 software.
RESULTS: Metastasis rates in the most commonly involved lymph nodes, the lateral retropharyngeal and IIb nodes, were 82.8% and 64.0%, respectively. Among patients with level IIb involvement, the upper borders of the metastatic nodes were beyond the caudal edge of C1 in 13.7% of cases. The parotid gland D50 and V26 values were significantly reduced after modifying the upper bound of level IIb used to delineate the CTV (P = 0.000).
CONCLUSIONS: In principle, the upper bound of level IIb should reach the lateral skull base during delineation of the cervical CTV for NPC. To protect the parotid glands, however, individualized reduction of the upper bound of level IIb is recommended for patients who meet certain criteria.
METHODS: From 2012 to 2016, 331 nonmetastatic NPC patients treated with IMRT were retrospectively enrolled. Based on the AJCC 8th staging system of NPC, there were 15 stage I, 76 stage II, 103 stage III, and 137 stage IV patients. The distribution of cervical lymph nodes in NPC was assessed based on imaging. Comparisons of the safety and parotid dose parameters between patients with and without a reduction in the size of level IIb were conducted using SPSS 25.0 and R 2.14.2 software.
RESULTS: Metastasis rates in the most commonly involved lymph nodes, the lateral retropharyngeal and IIb nodes, were 82.8% and 64.0%, respectively. Among patients with level IIb involvement, the upper borders of the metastatic nodes were beyond the caudal edge of C1 in 13.7% of cases. The parotid gland D50 and V26 values were significantly reduced after modifying the upper bound of level IIb used to delineate the CTV (P = 0.000).
CONCLUSIONS: In principle, the upper bound of level IIb should reach the lateral skull base during delineation of the cervical CTV for NPC. To protect the parotid glands, however, individualized reduction of the upper bound of level IIb is recommended for patients who meet certain criteria.
摘要：
目的：为鼻咽癌（NPC）患者接受调强放疗的临床靶区（CTV），推荐IIb级的颅骨边界，并帮助就CTV中IIb级的轮廓达成共识。
方法：从2012年至2016年，回顾性纳入331例非转移性鼻咽癌患者接受IMRT治疗。基于AJCC第8期NPC分期系统，有15个阶段，76第二阶段，103阶段III，和137名IV期患者。根据影像学评估NPC中颈部淋巴结的分布。使用SPSS25.0和R2.14.2软件对有和没有IIb级大小减少的患者之间的安全性和腮腺剂量参数进行比较。
结果：最常见的淋巴结转移率，咽后外侧和IIb淋巴结，分别为82.8%和64.0%，分别。在IIb级参与的患者中，在13.7%的病例中，转移性淋巴结的上边界超出C1的尾边缘。修改用于描绘CTV的水平IIb的上限后，腮腺D50和V26值显着降低（P=0.000）。
结论：原则上，在描绘NPC的宫颈CTV时，IIb水平的上限应到达侧颅底。为了保护腮腺,然而,对于符合某些标准的患者,建议个体化降低IIb水平的上限.
方法：从2012年至2016年，回顾性纳入331例非转移性鼻咽癌患者接受IMRT治疗。基于AJCC第8期NPC分期系统，有15个阶段，76第二阶段，103阶段III，和137名IV期患者。根据影像学评估NPC中颈部淋巴结的分布。使用SPSS25.0和R2.14.2软件对有和没有IIb级大小减少的患者之间的安全性和腮腺剂量参数进行比较。
结果：最常见的淋巴结转移率，咽后外侧和IIb淋巴结，分别为82.8%和64.0%，分别。在IIb级参与的患者中，在13.7%的病例中，转移性淋巴结的上边界超出C1的尾边缘。修改用于描绘CTV的水平IIb的上限后，腮腺D50和V26值显着降低（P=0.000）。
结论：原则上，在描绘NPC的宫颈CTV时，IIb水平的上限应到达侧颅底。为了保护腮腺,然而,对于符合某些标准的患者,建议个体化降低IIb水平的上限.
