前列腺癌质子调强与光子容积旋转调强放疗计划质量评估

Evaluation of plan quality for IMPT and VMAT in the treatment of patients with prostate cancer

目的研究基于计划靶区(PTV)的前列腺癌质子调强放疗(IMPT)计划与光子容积旋转调强放疗(VMAT)计划的剂量学特性,评估其计划质量差异,为临床应用提供参考。方法回顾性选取10例前列腺癌患者,分别用RayStation和Eclipse治疗计划系统基于PTV设计IMPT和快速旋转容积调强(RapidArc)计划,前者采用两平行对穿野进行多野优化(MFO),分别用笔形束(PB)和蒙特卡罗(MC)进行最终的剂量计算,数据模型源于IBA Protues Plus(IBA Group,比利时)笔形束扫描(PBS)质子治疗系统;后者采用双全弧计划,数据模型源于美国瓦里安Clinac iX直线加速器。通过剂量体积直方图(DVH)和剂量分布等比较两种治疗技术靶区和危及器官受量。结果对于靶区而言,PB-IMPT和MC-IMPT计划的均匀性指数(HI)均要略优于RapidArc计划,但适形度指数(CI)均要略低于RapidArc计划;PB-IMRT计划的D1%要明显的优于MC-IMPT和RapidArc计划,且差异均有统计学意义(Z=-2.805、-2.803,P<0.05);PB-IMPT和MC-IMPT计划在直肠V30(Z=-2.191、-1.988,P<0.05)和Dmean(Z=-2.599、-2.497,P<0.05),膀胱V30(Z=-2.701、-2.701,P<0.05)、V40(Z=-2.395、-2.395,P<0.05)和Dmean(Z=-2.701、-2.701,P<0.05)的保护上要优于RapidArc计划,且差异有统计学意义;对于前列腺癌PB-IMPT和MC-IMPT计划,除了靶区D1%(73.86±67.34)Gy(RBE)vs.(75.45±2.01)Gy(RBE)和HI(0.040±0.010 vs.0.058±0.020)有较明显差别外,其余两者之间差异无统计学意义(P>0.05)。结论两种不同的治疗技术均能满足临床治疗的要求,但IMPT计划相比RapidArc计划明显地降低了危及器官的受量,更好地保护了周围正常组织,提高了计划的质量,具有较为明显的剂量学优势。

Objective To study the dosimetric characteristics and plan quality of PTV-based intensity modulated proton radiotherapy(IMPT)and volumetric-modulated arc therapy(VMAT)plans for prostate cancer,so as to provide a reference for clinical application.Methods A total of 10 prostate cancer cases were included in this retrospective study.IMPT and RapidArc plans were designed by RayStation and Eclipse TPS based on PTV,respectively.For each case,IMPT plans were generated using multiple field optimization(MFO)technique with two parallel-opposed lateral fields,whereas RapidArc plans were generated using double-arc technique(two full arcs).Final dose calculation of IMPT was conducted by pencil beam(PB)and Monte Carlo(MC)algorithm,respectively,with adopted data model from the pencil beam scanning(PBS)proton therapy system of IBA Protues Plus(IBA Group,Belgium);The data model originated from the linear accelerator of Varian Clinac iX(Varian Medical Systems,America)was used for RapidArc plans.Dosimetric parameters of DVH and dose distribution were used to compare the dose differences in targets and organs at risk(OARs)between these two treatment techniques.Results For targets,HIs of PB-IMPT and MC-IMPT were slightly better than that of RapidArc,but CI of IMPT was slightly lower than that of RapidArc;D1%of PB-IMPT was significantly better than those of MC-IMPT and RapidArc(Z=-2.805,-2.803,P<0.05).PB-IMPT and MC-IMPT achieved better protection than RapidArc on rectum V30(Z=-2.191,-1.988,P<0.05)and Dmean(Z=-2.599,-2.497,P<0.05),bladder V30(Z=-2.701,-2.701,P<0.05),V40(Z=-2.395,-2.395,P<0.05)and Dmean(Z=-2.701,-2.701,P<0.05).There was no significant difference between PB-IMPT and MC-IMPT plans for prostate cancer,except for the D1%[(73.86±67.34)Gy vs.(75.45±2.01)Gy](RBE)and HI[(0.040±0.010)vs.(0.058±0.020)]of the target.Conclusions Both techniques can meet the clinical requirements,but IMPT showed significant dosimetric advantages compared with RapidArch by reducing the dose to OARs and improving the plan quality.