胸中段食管癌容积调强与螺旋断层放疗的剂量学比较

安义均; 赵彪; 赵玉涛; 和丽秋; 汤可维; 杨毅

doi:10.3969/j.issn.2095-5227.2018.04.011

摘要: 目的比较胸中段食管癌容积调强放疗（volumetric modulated arc therapy，VMAT）与螺旋断层放疗（tomotherapy，TOMO）的剂量学参数，为临床治疗选择提供剂量学参考。方法选取2015-2017年在我院治疗的19例未手术的男性胸中段食管患者。按统一标准进行靶区和危及器官（organs at risk，OAR）勾画，对同一患者分别设计VMAT计划和TOMO计划，通过剂量体积直方图（dose volume histogram，DVH）对两种计划的剂量学参数进行分析与比较。结果 VMAT与TOMO关于肿瘤靶区（gross tumor volume，GTV）与计划靶区（planning target volume，PTV）的GTV-D2（6 810.47±23.18） cGy vs （6 723.97±17.47） cGy、PTV-D2（6 765.93±53.94） cGy vs （6 656.61±23.18） cGy、GTV-D50（6 664.94±33.83） cGy vs （6 600.40±3.56） cGy、PTV-D50（6 113.57±188.91） cGy vs （5 954.81±29.64） cGy、GTV-适形性指数（GTV-Conformity index，GTV-CI）（48.42%±11.14% vs 63.16%±8.11%）、PTV-CI （68.37%±5.04% vs 75.47%±4.31%）、GTV-均匀性指数（GTV-Heterogeneity index，GTV-HI）（4.84%±0.96% vs 3.63%±0.50%）、PTV-HI （23.05%±1.31% vs 21.68%±0.49%）等差异均有统计学意义（P均< 0.05），而GTV-D98（6 480.54±55.61） cGy vs （6 487.91±27.38） cGy和PTV-D98（5 353.01±71.90） cGy vs （5 362.62±20.39） cGy无统计学意义（P均> 0.05）。在危及器官肺的比较上，VMAT较TOMO明显降低了左肺V₅（68.05%±4.13% vs 79.47%±7.79%）和平均剂量（1 290.71±92.73） cGy vs （1 368.53±141.50） cGy、右肺V₅（66.53%±4.21% vs 78.54%±8.70%）和平均剂量（1 264.59±109.66） cGy vs （1 344.32±98.61） cGy、双肺V₅（67.11%±3.80% vs 79.14%±8.25%）和平均剂量（1 290.71±98.61） cGy vs （1 368.53±95.92） cGy（P< 0.05）；但左肺V₃₀（10.42%±2.57% vs 8.66%±2.62%）、右肺V₃₀（9.79%±2.15% vs 8.70%±1.30%）、双肺V₃₀（10.42%±1.30% vs 8.66%±1.40%）明显高于TOMO （P< 0.05）；两者左肺V₂₀（21.79%±1.96% vs 22.01%±3.08%）、右肺V₂₀（20.11%±3.33% vs 20.02±1.97%）及双肺V₂₀（21.79±1.97 vs 22.01%±1.82%）差异无统计学意义（P> 0.05）。VMAT心脏V₃₀（16.63%±4.47% vs 12.96%±3.20%）和V₄₀（7.21%±1.69% vs 6.07%±1.88%）均高于TOMO （P< 0.05），但心脏平均剂量（1 832.32±394.64） cGy vs （1 836.37±533.59） cGy两者无统计学差异（P> 0.05）。VMAT计划的脊髓D2明显高于TOMO4 041.87±111.86） cGy vs （3 755.48±229.33） cGy（P< 0.05）。结论 TOMO计划及VMAT计划均能满足治疗要求，但TOMO计划能提供更好的适形性（conformity index，CI）与靶区均匀性（heterogeneity index，HI），而危及器官方面两种计划各有优势，应个体化制订。

Abstract: Objective To compare the dose distribution of volumetric modulated arc therapy (VMAT) versus tomotherapy (TOMO)for treatment of middle thoracic esophageal cancer patients, and provide basis for clinical decision. Methods Nineteen male patients with middle thoracic esophageal cancer who had not undergone esophageal surgery in our hospital from 2015 to 2017 were enrolled in this study. For each patient, the target and organs at risk (OAR) were delineated with the same criterion before VMAT and TOMO plans were designed. All dosimetric parameters of two plans were analyzed and compared by dose volume histogram (DVH). Results There were statistically significant differences in gross tumor volume (GTV) and planning target volume (PTV)between VMAT and TOMO (all P < 0.05), including GTV-D2(6 810.47±23.18) cGy vs (6 723.97±17.47) cGy, PTV-D2(6 765.93±53.94) cGy vs (6 656.61±23.18) cGy, GTV-D50(6 664.94±33.83) cGy vs (6 600.40±3.56) cGy, PTV-D50(6 113.57±188.91) cGy vs (5 954.81±29.64) cGy, GTV-Conformity index (GTV-CI)(48.42±11.14)% vs (63.16±8.11)%, PTV-CI(68.37±5.04)% vs (75.47±4.31%), GTV-Heterogeneity index (GTV-HI)(4.84±0.96)% vs (3.63±0.50)% and PTV-HI(23.05±1.31)% vs (21.68±0.49)%. However, no significant difference was found in GTV-D98(6 480.54±55.61) vs (6 487.91±27.38) cGy and PTV-D98(5 353.01±71.90) cGy vs (5 362.62±20.39) cGy (P> 0.05, respectively). As for OAR of lung, VMAT had lower left lung V5(68.05±4.13)% vs (79.47±7.79)%, left lung Dmean(1 290.71±92.73) cGy vs (1 368.53±141.50) cGy, right lung V5(66.53±4.21)% vs (78.54±8.70)%, right lung Dmean(1 264.59±109.66) cGy vs (1 344.32±98.61) cGy, double lung V5(67.11±3.80)% vs (79.14±8.25)% and double lung Dmean(1 290.71±98.61) cGy vs (1 368.53±95.92) cGy(all P < 0.05). However, VMAT achieved higher left lung V30(10.42±2.57)% vs (8.66±2.62)%, right lung V30(9.79±2.15)% vs (8.70±1.30)% and all lung V30(10.42±1.30)% vs (8.66±1.40)% compared to TOMO (all P < 0.05). Nevertheless, there was no significant difference in left lung V20(21.79±1.96)% vs (22.01±3.08)%, right lung V20(20.11±3.33)% vs (20.02±1.97)% and double lung V20(21.79±1.97)% vs (22.01±1.82)% between two techniques (all P > 0.05). Compared with VMAT, TOMO provided a superior protection for heart V30 and V40(16.63±4.47)% vs (12.96±3.20)%, (7.21±1.69)% vs (6.07±1.88)%, P < 0.05, respectively but failed to heart Dmean(1 832.32±394.64) cGy vs (1 836.37±533.59) cGy, P > 0.05. Spinal cord D2 was lower in TOMO than in VMAT(4 041.87±111.8) cGy vs (3 755.48± 229.33) cGy, P < 0.05. Conclusion Both VMAT and TOMO meet with the middle thoracic esophageal cancer patients' treatment needs, but TOMO further improves target's Conformity index (CI) and heterogeneity index (HI). Each of them has their own advantages for OAR sparing. Thus, radiotherapy techniques choosing should depend on patient's condition.

胸中段食管癌容积调强与螺旋断层放疗的剂量学比较

VMAT versus TOMO in dosimetric parameters for treatment of middle thoracic esophageal cancer