螺旋断层、容积旋转调强和固定野调强在食管癌放疗剂量对比分析

Dosimetric comparison of the helical tomotherapy,intensity-modulated radiotherapy and volumetric-modulated arc therapy in radical radiotherapy for esophageal cancer

目的对比螺旋断层放疗(TOMO)、容积旋转调强放疗(VMAT)和固定野调强放疗(IMRT)技术在食管癌放疗计划靶区及危及器官剂量参数之间的优劣。方法选择2015年9月至2016年5月在浙江省肿瘤医院接受放疗的25例食管鳞癌患者,男24例、女1例,47~82岁,中位年龄63岁。颈段+胸上段6例,胸中、下段19例。每例分别制作TOMO、VMAT和IMRT共3套放疗计划。所有计划均以计划靶体积(PTV)统一处方剂量6000 cGy/30F。记录PTV的适形指数(CI)、不均匀指数(HI)、最大剂量(Dmax)、平均剂量(Dmean),1%、2%、50%、95%、98%、99%PTV所受剂量D1、D2、D50、D95、D98、D99,95%,100%、105%处方剂量所围体积占比V95、V100、V105,全肺和心脏的平均剂量V5、V10、V20、V30、V40和V50,及脊髓的最大剂量(Dmax)。两正态分布数据间采用配对t检验进行比较。结果与TOMO及IMRT相比,VMAT显示了更高的适形指数(0.81±0.08)和更低的不均匀指数(0.10±0.05)。IMRT的适形指数为0.77±0.05,低于TOMO(0.79±0.04,t=2.604,P=0.016)及VMAT(0.81±0.08,t=2.817,P=0.010)。TOMO在正常肺组织各剂量学参数均低于VMAT和IMRT,尤其是在V20、V30(17.00%±5.57%,9.09%±3.93%)显著低于VMAT(18.12%±5.66%,10.18%±4.23%)(均P<0.05)和IMRT(21.46%±5.82%,11.87%±4.38%)(均P<0.01)。TOMO脊髓Dmax[(38.24±3.72)Gy]显著低于VMAT[(39.88±3.27)Gy,t=-3.173,P=0.004]和IMRT[(41.09±3.18)Gy,t=-5.559,P=0.000]。颈段、胸上段食管癌VMAT在适形指数和不均匀指数上好于TOMO和IMRT,尤其是不均匀指数(0.09±0.01)显著低于TOMO(0.12±0.03,t=3.024,P=0.029)和IMRT(0.12±0.02,t=-3.800,P=0.013)。TOMO和VMAT在肺平均剂量、V20、V30上低于IMRT,差异有统计学意义(均P<0.05)。TOMO在脊髓Dmax[(38.46±2.15)Gy]上明显低于VMAT[(41.02±1.28)Gy,t=-2.701,P=0.043]和IMRT[(41.76±1.11)Gy,t=-3.111,P=0.027]。胸中下段食管癌IMRT在肺MLD、V10、V20、V30上高于TOMO和VMAT(均P<0.05)。TOMO在脊髓Dmax[(38.17±4.14)Gy]上低于VMAT[(39.52±3.64)Gy,t=-2.219,P=0.040]和IMRT[(40.87±3.59)Gy,t=-4.528,P=0.000]。结论VMAT在靶区适形指数和不均匀指数优于TOMO和IMRT。TOMO在肺V20、V30和脊髓Dmax显著低于VMAT和IMRT。

Objective To compare the dosimetric parameters of three different modern radiation techniques in radical radiotherapy for esophageal cancer.Methods A total of 25 patients with pathologically confirmed esophageal squamous cell carcinoma in Zhejiang Cancer Hospital were included from September 2015 to May 2016 and three radiation treatment plans for helical tomotherapy(TOMO),intensity-modulated radiotherapy(IMRT)and volumetric-modulated arc therapy(VMAT)were designed respectively for each patient.Study patients included 24 males and 1 female,aged from 47 to 82 years old,with a median age of 63 years old.All patients received the total prescription dose of 60 Gy in 30 fractions to the planning target volume(PTV).Conformity index(CI),heterogeneity index(HI),D1,D2,D50,D95,D98,D99 and V95,V100,V105 of PTV was calculated.The mean dose,V5,V10,V20,V30,V40 and V50 of total lung,heart,and maximum dose(Dmax)to spinal cord were recorded as well.Results Compared with TOMO and IMRT,VMAT showed higher CI(0.81±0.08)and lower HI(0.10±0.05),and CI was worse in IMRT(0.77±0.05)than TOMO(0.79±0.04)(t=2.604,P=0.016)and VMAT(t=2.817,P=0.010).There was no significant difference in HI among three radiation techniques.The dosimetric parameters of TOMO in normal lung were significantly better than those of VMAT and IMRT,especially in V20 and V30.The Dmax of spinal cord(38.24±3.72)Gy in TOMO was significantly lower than that of the VMAT((39.88±3.27)Gy,t=-3.173,P=0.004)and IMRT plan((41.09±3.18)Gy,t=-5.559,P=0.000).Subgroup analysis showed that VMAT was superior to TOMO and IMRT in CI and HI,especially HI(0.09±0.01)significantly better than TOMO(0.12±0.03,t=3.024,P=0.029)and IMRT(0.12±0.02,t=-3.800,P=0.013)for patients with cervical and upper thoracic esophageal cancer.TOMO and VMAT were significantly better than IMRT in MLD,lung V20 and V30(all P<0.05).TOMO(38.46±2.15)Gy was significantly superior to VMAT((41.02±1.28)Gy,t=-2.701,P=0.043)and IMRT((41.76±1.11)Gy,t=-3.111,P=0.027)at Dmax of the spinal cord.For the patients with middle and lower thoracic esophageal cancer,TOMO,VMAT and IMRT had no statistically significant differences in CI and HI.IMRT was inferior to TOMO and VMAT in MLD,lung V10,V20,and V30(all P<0.05).TOMO(38.17±4.14)Gy was significantly superior to VMAT((39.52±3.64)Gy,t=-2.219,P=0.040)and IMRT((40.87±3.59)Gy,t=-4.528,P=0.000)at Dmax of the spinal cord.Conclusions The VMAT plan is better than TOMO and IMRT in terms of the conformal degree and dose uniformity of the target volume.TOMO seems significantly better than VMAT and IMRT in protecting normal tissue.