ICRU83号报告推荐方式评估宫颈癌术后辅助IMRT与传统放疗方式的差异及可行性

Difference and feasibility of intensity-modulated radiotherapy and conventional 2D radiotherapy for postoperative cervical cancer evaluated with ICRU 83 report method

目的以国际辐射单位与测量委员会(International Commission on Radiation Units and Measurements,ICRU)83号报告推荐的方式评估调强适形放疗(intensity-modulated radiotherapy,IMRT)方式与传统二维二野等中心放疗方式用于宫颈癌术后辅助放疗的差异及可行性。方法回顾性分析10例宫颈癌术后IMRT和模拟传统二维放疗的剂量体积直方图(dose-volume histogram,DVH)数据。统计计划靶区体积(planning target volume,PTV)、D100、D98、D95、D50、Dmean、D2、D0,计算均匀性指数(homogeneity index,HI);以D50评估不同放疗方式对剂量的影响;分别统计危及器官(organs at risk,OAR)的DVH参数并进行分析。结果以D50评估IMRT方式的PTV剂量较二维放疗方式提高4.47%±3.62%,其实际差值为(200±157)c Gy(t=4.2,P=0.001)。IMRT中骨盆的V10和V20高于二维放疗,V30的差异无统计学意义。IMRT中小肠的V10和V20高于二维放疗,V40低于二维放疗。IMRT中膀胱和直肠的V40、Dmean低于二维放疗,而以D1cc、D2cc、D2和Dmax为指标评估高剂量区,两种放疗方式的差异无统计学意义。结论 ICRU 83号报告推荐方式适用于IMRT计划评估;IMRT较传统放疗方式提高了靶区剂量,增加了骨盆和小肠的低剂量受照体积,降低了膀胱和直肠的整体受照剂量,但仍存在小体积较高剂量。若采用D50作为评估标准,可考虑降低剂量4.47%±3.62%。

Objective To evaluate the difference and feasibility of intensity-modulated radiotherapy and conven-tional 2D radiotherapy for postoperative cervical cancer with ICRU83 report method. Method The DVH parameters of 10 IMRT plans and 10 conventional 2D plans simulated on the same planning CT were analyzed retrospectively. The DVH parameters include D100, D98, D95, D50, Dmean, D2, D0 for PTV, and heterogeneity index was calculat-ed; the influence of different radiation modality on dose was assessed by V50; the DVH parameters of organs at risk were summarized and analyzed respectively. Result PTV D50 is raised by （4.47% ± 3.62%） in IMRT plans com-pared with 2D plans, the actual difference was （200 ± 157） cGy （t=4.2, P=0.001）. V10 and V20 for pelvic bones in IMRT was higher than that in 2D plans, V30 for pelvic bones in the two plans showed no statistical significance. V10 and V20 for small intestine were higher and V40 was lower in IMRT plans. V40 and Dmean were reduced in IMRT plans compared with 2D plans, while D1cc, D2cc, D2 and Dmax still remained as high dose volume, and there was no significant difference between the two therapies. Conclusion The method recommended by ICRU 83 report is applicable to IMRT plans. IMRT potentially increases dose to the target volume, increasing low-dose volume for small intestine and pelvic bones, while reducing dose for bladder and rectum, but small high dose volume still re-main. With D50 as a standard for dose evaluation, prescribed dose should be decreased by 4.47%±3.62%.