鼻咽癌调强放疗后颈部递推剂量限制可行性研究

Dose limitation of posterior neck of intensity modulated radiotherapy for nasopharyngeal carcinoma

目的鼻咽癌危及器官的勾画和限量受到广泛重视,但后颈部软组织勾画常被忽视。本研究旨在探讨后颈部递推剂量限制在鼻咽癌调强放疗(intensity modulated radiotherapy,IMRT)中的剂量学研究,并观察后颈部限制剂量与头颈部淋巴水肿(head and neck lymphedema,HNL)的关系,为鼻咽癌IMRT的后颈部危及器官勾画提供参考。方法选取2017-01-01-2019-08-31在南通大学附属建湖医院行IMRT的15例鼻咽癌患者,在后颈部勾画剂量限制区域(dose limitation area,DLA),每例采用单剂量爬坡法分别设计5组IMRT计划。计划Ⅰ的DLA未限制剂量,计划Ⅱ、Ⅲ、Ⅳ和Ⅴ的DLA分别<45、35、25和15Gy,按相同处方剂量和目标条件设计IMRT。比较多组靶区剂量分布、危及器官剂量和机器跳数方面的差异。观察放疗后头颈部淋巴水肿情况。结果计划Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ的计划靶区1(planning target volume 1,PTV1)的均匀性指数(homogeneity index,HI)差异无统计学意义;计划Ⅱ、Ⅲ、Ⅳ和Ⅴ的PTV1适形度指数(conformal index,CI)优于计划Ⅰ,且计划Ⅳ更好;计划Ⅱ、Ⅲ、Ⅳ和Ⅴ较计划Ⅰ明显减少后颈部高剂量照射体积,且计划Ⅳ、Ⅴ较计划Ⅱ、Ⅲ能够进一步减少后颈部低剂量照射体积。5组计划的脑干、脊髓、晶体、腮腺、口腔及气管等危及器官剂量差异均无统计学意义,且1程计划的机器跳数相似。计划Ⅳ为治疗计划,12例(80%)患者出现1级头颈部淋巴水肿。结论鼻咽癌IMRT在后颈部剂量限制能够明显减少高剂量体积照射,DLA合适的限制剂量为25Gy,靶区的CI更好,并能够进一步减少后颈部低剂量照射体积,以利于淋巴回流,减轻头颈部淋巴水肿。

OBJECTIVE The risk of organs is widely paid attentions in nasopharyngeal carcinoma(NPC)patients,but dose limitation area(DLA)of posterior neck is often ignored.This study aimed to research the dose limitation of posterior neck when intensity modulated radiotherapy(IMRT)of NPC,evaluate the relationship between dose and head and neck lymphedema(HNL),and provid clinical reference for NPC patients.METHODS Draw the outline of DLA in the posterior neck of fifteen NPC patients,there were five groups of IMRT plan with single dose climbing method.PlanⅠhad no dosage limitation of DLA.PlanⅡ,Ⅲ,ⅣandⅤhad separately dosage limitation with 45,35,25 and 15 Gy at each group,the prescription dose and target condition should be as same as PlanⅠ.Dose distribution of the target,dosevolume parameters of organ at risk(OAR)and the total monitor units(MU)were compared among the five groups.The occurrence of HNL was statistically analyzed.RESULTS The homogeneity index(HI)of PlanⅠ,Ⅱ,Ⅲ,ⅣandⅤwere no statistical significance.The conformal index(CI)of PlanⅡ,Ⅲ,ⅣandⅤwere better than that of PlanⅠand the CI of PlanⅣwas the best.Compared with PlanⅠ,PlanⅡ,Ⅲ,ⅣandⅤsignificantly reduced high dose irradiation volume in the posterior neck.PlanⅣandⅤcould further reduce low dose irradiation volume in comparison with PlanⅡandⅢ.The quantity difference of brainstem,spinal cord,crystalline lens,parotid gland,oral cavity and trachea had no statistical significance among five groups.The MU of 5 groups were similar.Fifteen patients were treated according to PlanⅣand 12 patients were subjected to grade 1 HNL.CONCLUSIONS The plan design with the dose limitation of posterior neck of IMRT for NPC patients can reduce high dose volume in the posterior neck.The dose limitation of 25 Gy may be better,which can further reduce low dose irradiation volume.