摘要目的 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D mean明显降低(P<0.05);虽然脑干D mean及颞叶D max明显降低,脊髓D mean和D max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D min和D mean均明显增加(P<0.05);颞叶D mean及脊髓D mean和D max明显降低,其中脊髓D max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.

abstractsObjective 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. Results Plan-1 vs. Plan-1-2:Plan-1-2 showed significantly reduced D meanof target volume compared with Plan-1(P<0.05). Plan-1-2 significantly increased D meanand D maxof the spinal cord(P<0.05),although significantly reduced D mean of the brain stem and D maxof 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 D meanand D minof gross tumor volume(GTV)and primary GTV(P<0.05)and significantly reduced D meanof the temporal lobes and D maxand D meanof the spinal cord(P<0.05), with D max 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). Conclusions IMRT plan-1 after IC has worse dosimetric distribution,while replanning after IC has more dosimetric benefits.