一种新的子宫内膜癌术后全盆腔适形弧放射治疗技术

A novel conformal arc radiotherapy technique for postoperative whole pelvic radiotherapy of endometrial cancer

目的:探索和评价一种新的子宫内膜癌术后全盆腔适形弧放射治疗技术。方法:采用新适形弧技术将计划靶区矢状面体中线2侧各删除宽1.25cm的区域,以生成左右2个剂量成形结构,分别以2个剂量成形结构及其中心为靶区及等中心设计2个180°适形弧。通过对10例子宫内膜癌患者2个等中心的适形弧治疗(two-axis conformalarc therapy,2A-CAT)、三维适形放疗和调强放疗计划的剂量分布进行比较,对2A-CAT进行剂量学评价。结果:适形弧、三维适形和调强放疗计划的平均适形度指数分别为0.83、0.61和0.88,均匀性指数分别为1.15、1.08和1.10。适形弧计划中小肠+结肠、直肠、膀胱和盆腔骨的平均照射剂量较三维适形放疗计划分别低1.19、3.39、4.65和1.64Gy,但较调强放疗计划略高。适形弧计划中正常组织的平均照射剂量较调强放疗计划高1.87Gy,差异有统计学意义(P<0.01),而与三维适形放疗计划的差异无统计学意义。结论:新适形弧放射治疗技术与三维适形放疗技术相比,可明显改善剂量分布的适形度和对危及器官的保护,但较调强放疗技术略差。

Objective：To explore and evaluate a novel conformal arc radiotherapy technique for postoperative whole pelvic radiotherapy of endometrial cancer.Methods：The technique involves two-axis conformal arc therapy （2A-CAT） with 180 degree rotation around two isocenters each in two separate dose shaping structures,which were formed by cutting off the central 2.5 cm area of planning target volume （PTV） in the sagittal plane of the body. In order to produce concave and conformal dose distributions to protect the organs at risk,these two dose shaping structures were considered as the target volume for the dynamic multileaf collimator （MLC） instead of the PTV itself. Dosimetric comparison of this new 2A-CAT technique with three-dimensional conformal radiotherapy （3DCRT） and intensity-modulated radiotherapy （IMRT） was performed in ten patients with endometrial cancer. Results：The mean conformity index was 0.83,0.61,and 0.88 for the 2A-CAT,3DCRT,and IMRT plans,respectively. The mean homogeneity index was 1.15,1.08 and 1.10,respectively. The mean dose to small bowel and colon,rectum,bladder and pelvic bones in 2A-CAT was 1.19 Gy,3.39 Gy,4.65 Gy,and 1.64 Gy lower than that of 3D-CRT （P〈0.05）,but a little higher than that of IMRT. The mean dose to normal tissue in 2A-CAT was 1.87 Gy higher than that of IMRT （P〈0.01）. The difference in mean dose to normal tissue between 2A-CAT and 3D-CRT was not significant. Conclusion：Compared with 3DCRT,the 2A-CAT technique significantly improves the dose conformity and gives more protects on the organs at risk,although there is still a space for improvement compared with IMRT.