诱导化疗对局部晚期鼻咽癌IMRT剂量学影响及再计划剂量学特点分析

Dosimetric impact of induction chemotherapy on intensity-modulated radiotherapy for locally advanced nasopharyngeal carcinoma and dosimetric characteristics of replanning

目的 通过研究诱导化疗对局部晚期鼻咽癌IMRT剂量学的影响及诱导化疗后再计划的剂量学特点,探讨诱导化疗后再计划的优特点,为临床合理设计放疗计划提供数据。方法 16例鼻咽癌患者诱导化疗前后各行1次增强CT扫描定位,并分别勾画靶区和制作放疗计划,分别定义为Plan-1及Plan-2。将诱导化疗后的靶区结构拷贝到第1段计划,融合生成第3段靶计划,定义为Plan-1-2。配对t检验Plan-1与 Plan-1-2、Plan-2与Plan-1-2靶计划的剂量学参数差异。结果 Plan-1与Plan-1-2：Plan-1-2 靶区Dmean明显降低（P〈0.05）;虽然脑干Dmean及颞叶Dmax明显降低,脊髓Dmean和Dmax均明显增加（P〈0.05）;靶区CI明显降低,HI明显增加（P〈0.05）;Plan-2与Plan-1-2：Plan-2 GTV、PGTV的Dmin和Dmean均明显增加（P〈0.05）;颞叶Dmean及脊髓Dmean和Dmax明显降低,其中脊髓Dmax降低达430.48 cGy （P〈0.05）;靶区CI明显增加,HI明显降低（P〈0.05）。结论 诱导化疗后第1段IMRT靶计划剂量学分布变差,诱导化疗后再计划更有剂量优势。

Objective To investigate the benefits of replanning after induction chemotherapy （IC） by analyzing the dosimetric impact of IC on intensity-modulated radiotherapy （IMRT） for locally advanced nasopharyngeal carcinoma （NPC） and the dosimetric characteristics of replanning after IC, and to provide data for the rational design of clinical radiotherapy plans. Methods 16 NPC patients underwent contrast-enhanced CT scan once before and after IC. Target volumes were delineated and the chemotherapy plans were created, defined as Plan-1 and Plan-2, respectively. Then the target structure after IC was copied to Plan-1, generating the third plan, defined as Plan-1-2. The paired t-test was used to compare the dosimetric parameters between Plan-1 and Plan-1-2 and between Plan-2 and Plan-1-2. Resutls Plan-1 vs. Plan-1-2：Plan-1-2 showed significantly reduced Dmean of target volume compared with Plan-1（P〈0.05）. Plan-1-2 significantly increased Dmean and Dmax of the spinal cord （P〈0.05）, although significantly reduced Dmean of the brain stem and Dmax of the temporal lobes compared with Plan-1. Plan-1-2 also had significantly reduced conformity index （CI） and significantly increased homogeneity index （HI） for the target volume compared with Plan-1（P〈0.05）. Plan-2 vs. Plan-1-2：Compared with Plan-1-2, Plan-2 significantly increased Dmean and Dmin of gross tumor volume （GTV） and primary GTV （P〈0.05） and significantly reduced Dmean of the temporal lobes and Dmax and Dmean of the spinal cord （P〈0.05）, with Dmax decreased to 430.48 cGy;Plan-2 had significantly increased CI and significantly reduced HI for the target volume compared with Plan-1-2（all P〈0.05）. Conclutions IMRT plan-1 after IC has worse dosimetric distribution, while replanning after IC has more dosimetric benefits.