胰腺癌质子调强与光子容积旋转调强计划的剂量学比较

Comparisons of dose distributions between IMPT and VMAT for pancreatic cancer

目的比较质子调强和光子容积旋转调强在胰腺癌大分割放射治疗计划中的剂量学差异。方法回顾性选取10例胰腺癌患者临床资料,分别使用Eclipse和RayStation进行容积旋转调强治疗(VMAT)和质子调强治疗(IMPT)的计划设计。完成计划后的剂量文件统一导入MIM软件以提取评估参数。主要评估参数包括计划靶区(PTV)的D_(min)、D_(mean)、D_(max)、适形指数(CI)和新适形指数(nCI)、均匀指数(HI)、梯度指数(GI)、覆盖率(coverage)和危及器官的受照剂量。结果靶区方面两组的适形性差异无统计学意义(P>0.05),VMAT组取得了更高的PTV D_(min)、D_(max)、D98%、D2%、HI和覆盖率以及更优的剂量梯度GI和D2 cm(t/Z=-4.63~5.32,P<0.05),IMPT组则获得了更低的10%_PD(t=-7.47,P<0.05)。危及器官方面,两组的空回肠最大剂量D_(max)、胃D_(max)、十二指肠D_(max)以及左肾的平均剂量D_(mean)差异无统计学意义(P>0.05)。IMPT组在空回肠的体积剂量D_(5 cm^(3))、胃的D_(10 cm^(3))、十二指肠的D_(5 cm^(3))及D_(10 cm^(3))、左肾的D_(2/3)、右肾的D_(mean)及D_(2/3)上均低于VMAT组(t/Z=-8.12~-2.60,P<0.05),但是IMPT组脊髓的D_(max)和D_(0.35 cm^(3))均高于VMAT组(t=7.30、6.77,P<0.05)。结论VMAT和IMPT都能实现满足临床要求的胰腺癌大分割放射治疗计划。二者在在毗邻胰腺靶区的胃肠道组织最大受量上的保护无差异,在胃肠道的体积受量保护上IMPT拥有更大优势,但对射束肿瘤靶区前缘的危及器官保护上可能弱于VMAT。

Objective To compare dose distributions of hypofractionated radiotherapy for pancreatic cancer between IMPT and VMAT.Methods Ten pancreatic cancer cases were included in this retrospective study.Photon(Edge)and proton(Proteus®PLUS)plans were designed by Eclipse and RayStation TPS,respectively.All plans were transferred to MIM system for extraction of parameters,which included D_(min),D_(mean)and D_(max)of PTV,conformity index(CI),new conformity index(nCI),homogeneity index(HI),gradient index(GI),coverage,D_(max)and dose-volume of the organs at risk(OARs).Results There was no significant difference in CI between the two groups.The higher PTV D_(min),D_(mean),D_(max),D98%,D2%,HI,coverage and the better GI,D2 cmwere found in VMAT(t/Z=-4.63-5.32,P<0.05).The lower 10%_PD was found in IMPT(t=-7.47,P<0.05).Regarding the OARs,D_(max)of the intestine,stomach,and duodenum and D_(mean)of the left kidney were similar between two groups without significant difference(P>0.05).The D_(5 cm^(3))of the intestine,D_(10 cm^(3))of the stomach,D_(5 cm^(3))and D_(10 cm^(3))of the duodenum,D_(2/3)of the left kidney,D_(mean)and D_(2/3)of the right kidney were lower in IMPT than those in VMAT(t/Z=-8.12--2.60,P<0.05).However,the D_(max)and D_(0.35 cm^(3))of the spinal cord were higher in IMPT than those in VMAT(t=7.30,6.77,P<0.05).Conclusions Both of hypofractionated radiotherapy plans of pancreatic cancer designed by VMAT and IMPT could meet clinical needs.No significant difference was found in D_(max)of the adjacent gastrointestinal tracts between the two groups.While IMPT had the advantage over VMAT in the case of lower dose-volumes of the gastrointestinal tracts.Nevertheless,less protections of the OARs in front of the tumor volume could be provided by IMPT compared with VMAT.