前列腺癌重碳离子放疗计划与调强放疗计划的比较

目的比较前列腺癌重碳离子放疗（C-ion RT）与调强放疗（IMRT）在剂量学方面的差异。方法随机选取5例前列腺癌患者,分别设计4野共面的C-ion RT计划和7野共面的IMRT计划。剂量均采用百分剂量,95％的等剂量面必须包括100％的计划靶体积（PTV）。比较靶区剂量分布的适形度指数（CI）和异质性指数（IC）,根据剂量体积直方图（DVH）,比较相同剂量水平下C-ion RT计划与IMRT计划中周围器官及非靶区正常组织的照射体积。结果在C—-ion RT计划中,CI50%、CI94%、IC分别为3．36、1．20和0．03,与IMRT计划比较差异有统计学意义（P均〈0．01）,靶区剂量分布的CI和IC均优于IMRT计划。除了95％的剂量水平外,在10％、30％、50％、70％和90％剂量水平,采用C—ion RT均可明显减少直肠的受照射体积（P均〈0．05）,同时完全保护直肠的后壁;在任何剂量水平,C—ion RT可明显减少膀胱和非靶区正常组织的受照射体积（P均〈0．05）;在10％、20％、30％和40％剂量水平,C—ion RT可明显减少双侧股骨头的受照射体积（P均〈0．05）。结论在前列腺癌的放射治疗中,与IMRT计划相比,C—ion RT计划在剂量学方面有明显优势,C—ion RT的这些优势将能够进一步提高前列腺癌的局部控制率,减少放疗引起的并发症。

Comparison of treatment planning by carbon ion radiotherapy and by intensity-modulated radiotherapy for prostatic adenocarcinoma

Objective To evaluate the potential benefit of carbon ion radiotherapy (C-ion RT) through comparison with photon intensity-modulated radiotherapy(IMRT)in dose distribution for prostatic adenoearcinoma.Methods In randomly selected 5 patients,treatment planning of C-ion RT (4 coplanar beams) and IMRT(7 coplanar fields)were worked out by computer working station.In order to make a meaningful comparison,it was defined that the 95% isodose surface had to cover 100% of the PTV in each plan;all dose was given as normalized dose with the definition of the minimum dose of the PTV being equal to 95% of prescribed dose.Dose-volume histograms (DVHs)of the tumor and organ-at-risks (OARs) were calculated.Volume irradiated more than or equal to some specified doses,conformity index ( CI ),and inbomogeneity coefficient (IC) of each treatment plan was compared,respectively.Results With C-ion RT,the mean irradiated volumes (in% ) of the rectum were significantly smaller than that with IMRT except for 95% dose level,and C-ion RT could provide complete protection to the posterior rectal wall.In addition,C-ion RT could also remarkably reduce the dose to the bladder,femoral heads and non-target normal tissues at each dose level.Dose conformation and homogeneity in the target volume of C-ion RT were better than that in IMRT ( mean CI_(50%),3.36 vs.5.04,mean CI_(95%),1.20 vs.1.46,mean IC,0.03 vs. 0.12).Conclusion Compared with IMRT,C-ion RT can obtain better dose distribution,and may reduce tumor recurrence and radiation-induced complications in prostatic adenocarcinoma.