鼻咽癌调强放疗临床靶区中Ⅳ区优化对甲状腺剂量的影响

Effect of optimizing clinical target volume in neck node level Ⅳ on thyroid dose in nasopharyngeal carcinoma

目的评估鼻咽癌调强放疗临床靶区中Ⅳ区优化的安全性以及对甲状腺剂量的影响,为鼻咽癌调强放疗靶区的优化提供依据。方法选取64例接受调强放疗的鼻咽癌患者,分为Ⅳ区优化组（CTV不包含Ⅳ区）和非优化组（Ⅳ区仍在CTV范围内）各32例;采用治疗计划系统测量甲状腺的放疗剂量参数,比较优化组与非优化组之间,以及不同临床期别、T分期和N分期之间甲状腺的剂量参数;用Kaplan-Meier法进行生存分析。结果鼻咽癌患者合理优化Ⅳ区未降低区域局控率,且可以显著降低甲状腺的平均剂量以及体积百分剂量V50（P〈0.05）;Ⅳ期患者的甲状腺平均剂量及V50显著高于其余各期别,N0~2期患者中Ⅳ区优化组的甲状腺平均剂量及V50显著低于非优化组。结论鼻咽癌患者合理优化临床靶区中Ⅳ区的范围是安全的,可更好地保护甲状腺。

Objective To assess the effect of optimizing the neck node level Ⅳ in IMRT clinical target volume（ CTV） for nasopharyngeal carcinoma（ NPC） on the treatment outcome and thyroid dose,in order to provide the basis for optimization of IMRT target area in NPC. Methods For selected 64 cases of NPC patients treated with IMRT,including 32 cases of neck node level Ⅳ region which optimized,and a control group of 32 cases which Ⅳ region is still within the CTV; Radiation dose parameters of thyroid were measured using treatment plan system for all patients. These radiation dose parameters of thyroid were compared between optimization and no optimization groups,as well as among different clinical stages,T and N stages,respectively. Meanwhile,a survival analysis was performed using Kaplan-Meier method. Results Reasonably optimizing the neck node level Ⅳ in CTV can significantly reduce the thyroid mean dose and volume percent dose V50（ P〈0. 05） and does not decrease the local control probability. The thyroid mean dose and V50 of patients with stage Ⅳ were much higher than those with other stages,and for the N0-2patients,optimization of neck node level Ⅳ in CTV can significantly reduce the thyroid mean dose and V50 comparing with no optimization group. Conclusion For NPC patients,reasonably optimizing the neck node level Ⅳ in CTV is safe and can much better protect the thyroid gland.