颈段、胸上段食管癌3DCRT/IMRT剂量学比较

摘要

目的 通过对颈段、胸上段食管癌三维适形(3DCRT)和调强(IMRT)放疗计划的剂量学比较,选择符合临床要求的最优方案.方法 14例颈段、胸上段食管癌患者模拟定位后参考食管钡餐和内镜检查结果勾画GTV,按照统一标准确定CTV、PTV,分别设计3DCRT、5野均匀分布IMRT-A和5野非均匀分布IMRT-B共3套放疗计划,以95％ PTV获得100％处方剂量进行归一,分析各计划靶区剂量分布及危及器官受量的差异.结果 本组病例所有的IMRT计划均能满足治疗要求,而4例3 DCRT计划不能满足要求,本研究仅对10组可行计划进行进一步的剂量学比较.预防照射区(PTV1):3DCRT计划的剂量参数Dmesn、D100、D95分别为(5725±54.96)cGy、(4703±25.26)cGy、(5203±71.70)cGy,明显高于IMRT-A的(5348±27.14)cGy、(4158±27.36)cGy、(4996±54.74)cGy和IMRT-B的(5232±26.85)cGy、(4286±12.13)cGy、(4979±31.78)cGy (P＜0.05);3DCRT Vl05为(82.95±3.02)％,高于IMRT-A的(71.07±6.68)％和IMRT-B的(69.55±4.56)％(P＜0.05),V10o、V95无明显差异(P＞0.05).肿瘤区(PTV2):3套放疗计划的Dmean、D100、D95、V105、V95无明显差异(P＞0.05),而IMRT-A和IMRT-B的V1oo分别为(95.21±1.78)％和(96.12±2.55)％,均高于3DCRT的(88.69±1.84)％(P＜0.05);IMRT-A和IMRT-B HI分别为1.08±0.01和1.02±0.01,低于3DCRT的1.18±0.03,差异有统计学意义(P＜0.05).除肺V5外,IMRT-A和IMRT-B脊髓Dmax、肺V20、V30、MLD分别为(3641±23.41)cGy、(22.08±0.31)％、(11.07±0.51)％、(1034±37.51)cGy和(3303±75.39)cGy、(19.82±1.74)％、(10.14±1.20)％、(981±38.16)cGy,均小于3DCRT的(4113±38.28)cGy、(28.07±6.30)％、(19.72±5.26)％、(1356±38.91)cGy,差异具有统计学意义(P＜0.05).IMRT计划剂量参数、体积参数、剂量分布均匀性无明显差别(P＞0.05);1MRT-B肺MLD和脊髓Dmax较IMRT-A低,差异具有统计学意义(P＜0.05).结论颈段、胸上段食管癌放疗采用IMRT优于3DCRT,根据靶区形状非均匀布野IMRT可进一步降低肺和脊髓受照剂量.%Objective To select the optimal radiotherapy plan for cervical and upper-thoracic esophageal cancer through dosi-metric comparison between 3DCRT and IMRT plans. Methods Fourteen patients with cervical and upper-thoracic esophageal cancer underwent CT simulation. GTV was contoured referring the esophagogram and endoscopy simultaneously, then CTV and PTV were de fined by the uniform standards. A 3DCRT plan and two five-fields IMRT plans consisting of conventional uniform bean angles and non uniform beam angles were designed respectively. Dose distribution of the PTV and OARs in different plans were compared under the premise that 95% of PTV volume received 100% prescription dose. Results All the IMRT plan could meet the requrements, but 4 of the 3DCRT plan (4/14) could not meet the requrements, so only 10 group of treatment pains in this study were feasible for further Do simetric comparison. For PTV 1, the dose parameters D,^, D^ , DM of 3 DCRT plans were 5725 ± 54. 96 cGy, 4703 ± 25. 26 cGy, 5203 ±71. 70 cGy, which were higher than those in IMRT-A(5348 ±27. 14 cGy,4158 ±27. 36 cGy,4996 ±54. 74cGy)and IMRT-B (5232±26.85 cGy,4286±12. 13 cGy,4979 ±31. 78 cGy),showing significant differences (P < 0.05). The size parameters V105 in 3DCRT was 82. 95 ±3.02% , which was higher than that in IMRT-A 71.07 ±6.68% and IMRT-B 69. 55 ±4. 56% .showing signifi cant differences(P<0.05). There was no significant difference in V100 and V95 among the three plans (P>0.05). For PTV2, there was no significant difference in Dmean, D100, D95, V105 and V95(P>0.05), but the size parameters V100 in IMRT-A and IMRT-B were 95. 21 ± 1. 78% and 96. 12 ±2. 55% , which was significantly higher than 3DCRT(88. 69 ± 1. 84% ), showing significant differences (P<0.05). For dose distribution, IMRT was better than 3DCKt(P <0.05). The maximum dose of spinal cord, lung V20,V30 and MLD in 1MRT-A and IMRT-B were 3641 ±23. 41 cGy, 22. 08 ±0. 31% , 11. 07 ±0. 51% , 1034 ±37. 51% and 3303 ±75. 39 cGy, 19. 82 ± 1. 74% , 10. 14 ± 1. 20% , 981 ±38. 16 cGy, which were lower than 3DCRT(4113 ±38. 28 cGy, 28. 07 ±6. 30% , 19. 72 ± 5.26% , 1356 ±38.91 cGy), showing significant differences( P <0. 05). There was no significant difference between the two IMRT plans in dose parameters, size parameters and dose distribution(P > 0.05). But, MLD and the maximum dose of spinal cord could be re duced by the non-uniform beam angles IMRT plans(P <0. 05). Conclusion IMRT plan is better than 3DCRT plan for cervical and upper-thoracic esophageal cancer, non-uniform beam angles IMRT plans design according to the target can reduce the exposure dose of lung and spinal cord.