摘要目的：探讨鼻咽癌IMRT的CTV中Ⅱb 区的上界，并寻找个体化缩减Ⅱb 区范围的标准。方法回顾分析2012—2014年收治的142例（ AJCC 2010分期标准Ⅰ、Ⅱ、Ⅲ、Ⅳ期分别为8、37、41、56例）初治鼻咽癌患者采用IMRT情况。根据影像阅片研究鼻咽癌颈部淋巴结分布规律。比较缩减Ⅱb 区范围者与未缩减者腮腺剂量参数差异并t检验及t＇检验。结果咽后外侧淋巴结和Ⅱb 区淋巴结是最常见受累淋巴结，转移率分别为75?4％和67?6％。在Ⅱb 区受累患者中51?0％出现了高位阳性淋巴结，6?3％阳性淋巴结上界超过了RTOG分区定义的Ⅱb 区上界。对符合拟定标准患者缩减Ⅱb 区范围是安全的，优化靶区后可显著降低腮腺D50、V26（ P＝0?000）。结论在勾画鼻咽癌颈部CTV时，原则上Ⅱb 区上界应至侧颅底，但对符合拟定标准者可个体化缩减Ⅱb 区上界，以更好地保护腮腺。

abstractsObjective To explore the upper bound of Ⅱb region in the clinical target volume ( CTV ) for intensity?modulated radiotherapy ( IMRT ) for nasopharyngeal carcinoma ( NPC ) , and to establish a standard for personalized reduction in the range ofⅡb region. Methods A retrospective analysis was performed on the IMRT results of 142 patients newly diagnosed with NPC who were admitted to our hospital from 2012 to 2014. According to the American Joint Committee on Cancer 2010 staging system, there were 8 patients with stageⅠ disease, 37 stage Ⅱ, 41 stage Ⅲ, and 56 stage Ⅳ. The distribution pattern of cervical lymph nodes in NPC was studied based on the imaging results. Comparison of the dose to parotid glands between patients with and without reduction in the range ofⅡb region was made by t test and t'test. Results The metastasis rates of the most common diseased lymph nodes, lateral retropharyngeal lymph node and Ⅱb lymph node, were 75?4% and 67?6%, respectively. In the patients with metastases inⅡb region, 51?0% had high?risk positive lymph nodes and 6?3% had positive lymph nodes beyond the upper bound of Ⅱb region defined by the Radiation Therapy Oncology Group system. It was safe to narrow down Ⅱb region in patients who met the formulated standard. The D50 and V26 values for parotid glands were significantly reduced after optimization of CTV ( P=0?000) . Conclusions The upper bound ofⅡb region, in principle, should reach the lateral skull base during the delineation of the cervical CTV for NPC. In order to protect the parotid glands, however, personalized reduction in the upper bound of Ⅱb region is recommended for patients who meet the formulated standard.