鼻咽癌放疗中自适应再计划体积与剂量的变化

The changes of volume and dose in adaptive re-planning during radiotherapy for nasopharyngeal carcinoma

目的探讨鼻咽癌(NPC)放疗中自适应再计划的必要性和对剂量的改善。方法回顾性分析2014年7月—2017年12月中山大学肿瘤防治中心的89例NPC患者数据,患者均接受25+7分次的自适应再计划放疗。比较第一次CT扫描设计的放疗计划(计划A,25分次)与重新扫描CT后设计的自适应放疗计划(计划B,7分次)之间靶区和腮腺体积的改变。比较由计划A模拟扩展成32分次放疗的一次性计划(计划Ⅰ)与由计划A和计划B配准融合叠加生成的自适应再计划(计划Ⅱ)的靶区剂量学、均匀性指数、适形指数(CI)差异和危及器官(OAR)的剂量学差异。主要采用配对t检验进行统计分析。结果与计划A相比,计划B的大出血病变的大体肿瘤体积(GTVnx)和腮腺体积分别缩小13.14%和11.12%,转移淋巴结的计划临床靶区(PCTVnd)增大了7.75%(均为P<0.001)。计划Ⅱ中大出血病变计划靶区(PTVnx)的Dmean、D5%、D95%和高危计划靶区(PTV1)的D5%与计划Ⅰ相比均明显增大(均为P<0.05);计划Ⅱ中PTVnx和PTV1的CI比计划Ⅰ更接近1。在所有评估的OAR中,计划Ⅱ的Dmean、D50%、Dmax均明显比计划Ⅰ小(均为P<0.05)。结论放疗过程中,NPC患者会发生不同程度的原发肿瘤缩小、腮腺萎缩和淋巴结改变,再计划在放疗过程中是需要的,且能明显改善靶区和OAR的剂量。

Objective To investigate the necessity of adaptive re-planning during radiotherapy for nasopharyngeal carcinoma(NPC)and its impact on dose improvement.Methods Clinical data of 89 NPC patients admitted to Sun Yat-sen University Cancer Center from July 2014 to December 2017 were retrospectively analyzed.All patients received 25+7 rounds of adaptive re-planning during radiotherapy.Plan-A was defined as the initial CT scan-based 25-fraction radiotherapy plan,while plan-B was defined as the re-planned 7-fraction radiotherapy plan based on a subsequent CT scan.The changes in the target and parotid gland volumes were compared between plan-A and plan-B.Plan-I was a one-time simulation of plan-A extended to 32 fraction radiotherapy plan,and plan-II was generated through registration and fusion of the plan-A and plan-B for adaptive re-planning.The differences in dose metrics,homogeneity index(HI),conformity index(CI),and dose to organs at risk(OAR)were compared between plan-I and plan-II.Statistical analysis was performed by using paired t-test.Results Compared with plan-A,the gross tumor volume of massive bleeding lesions(GTVnx)and parotid gland volume of plan-B were decreased by 13.14%and 11.12%,respectively(both P<0.001).While planning clinical target volume of metastatic lymph nodes(PCTVnd)of plan-B was increased by 7.75%(P<0.001).There were significant changes in the lymph nodes of plan-A and plan-B.The Dmean,D5%,D95%of massive bleeding lesions planning target volume(PTVnx)and D5%of high risk planning target volume(PTV1)in plan-II were all significantly higher than those in plan-I(all P<0.05).The CI of PTVnx and PTV1 in plan-II was closer to 1 than that in plan-I.In all assessed OAR,the Dmean,D50%,and Dmax of plan-II were significantly lower than those of plan-I(all P<0.05).Conclusions During radiotherapy,NPC patients may experience varying degrees of primary tumor shrinkage,parotid gland atrophy,and lymph node changes.It is necessary to deliver re-planning and significantly improve the dose of target areas and OAR.