40例N_(2)期鼻咽癌Ⅳ区淋巴结选择性照射保护甲状腺功能的临床分析

Effect of Nodal Selective Irradiation in Clinical Target Volume Ⅳ on Protecting Thyroid Function of 40 Patients with N_(2) Nasopharyngeal Carcinoma

[目的]探讨鼻咽癌N_(2)期患者行Ⅳ区靶区范围缩减的可行性以及对甲状腺保护的剂量优势。[方法]选取2015年3月至2017年4月收治的目前仍生存的鼻咽癌N_(2)患者40例作为研究对象,其中根据甲状腺周围颈动脉鞘淋巴结分布以及Ⅲ区淋巴结状态进行Ⅳ区靶区内界和/或下界优化的34例患者纳入优化组。收集全部患者的一般临床特征、影像学资料、甲状腺功能资料及放疗剂量参数,分析靶区范围优化对甲状腺功能的影响。[结果]40例患者中位随访时间为63个月,放疗后甲状腺功能减退(简称甲减)发生率为45.0%(18/40),其中亚临床型甲减15例(37.5%),临床型甲减3例(7.5%),出现时间为放疗后4~48个月(中位时间13个月);优化组甲减发生率为35.3%(12/34),均为亚临床型甲减。仅有2例(5.0%)患者甲状腺周围颈动脉鞘前方有可辨认淋巴结;分别有29例(72.5%)及38例(95.0%)患者颈动脉鞘后方及外方有可辨认淋巴结,颈动脉鞘后方、外方最内侧淋巴结距甲状腺外侧缘的中位距离分别为9.5(5~21)mm、18(10~34)mm;优化组甲状腺D_(mean)及V_(30)均低于非优化组,Ⅳ区内界及下界均优化患者与未优化组患者的D_(mean)及V_(30)有显著性差异(P<0.01),全部病例均未出现颈部淋巴结复发。[结论]对鼻咽癌晚N分期患者进行合理优化颈部Ⅳ区临床靶区范围,在无淋巴结分布区域免除照射是安全可行的,可以更好地保护甲状腺功能。

[Objective]To determine the feasibility ofⅣlevel target reduction and the dose advantage for thyroid protection in patients with N_(2) nasopharyngeal carcinoma.[Methods]Forty cases with N_(2) nasopharyngeal carcinoma from March 2015 to April 2017 were selected,according to the distribution of perithyroidal carotid sheath lymph nodes and the status ofⅢlevel lymph nodes,34 media and/or caudal boundary optimized patients inⅣlevel were included in the optimization group.The general clinical features,imaging data,thyroid function data,and radiotherapy dose parameters of all patients were collected to analyze the effect of optimization on thyroid function.[Results]The median follow-up time was 63 months.The incidence of hypothyroidism was 45.0%(18/40),including 15 cases(37.5%)of subclinical hypothyroidism and 3 cases(7.5%)of clinical hypothyroidism,occurred from 4 to 48 months after railiotherapy(median time was 13 months).The incidence of hypothyroidism in the optimized group was 35.3%(12/34),all of which were subclinical hypothyroidism.Only 2 patients(5.0%)had identifiable lymph nodes anterior to the carotid sheath around the thyroid gland;29 patients(72.5%)and 38 patients(95.0%)had lymph nodes posterior and lateral to carotid sheath,respectively,and the distance from the most medial lymph node posterior or lateral to the lateral edge of the thyroid gland was 9.5(5~21)mm and 18(10~34)mm.The D_(mean) and V_(30) of thyroid gland in the optimized group were lower than those in the non-optimized group.There was significant difference between the double boundary optimized patients and the non-optimized patients(P<0.01).No recurrence of cervical lymph nodes in the whole group.[Conclusion]It is safe and feasible to optimize the CTV range and spare irradiation in areas without lymph node distributionin cervicalⅣlevel in patients with advanced N stage of nasopharyngeal carcinoma,which can better protect thyroid function.