胸段食管癌患者三种放疗计划心脏和肺的剂量学比较

Dosimetric comparison on heart and lung among three modalities in treatment of thoracic esophageal cancer

目的 比较胸中下段食管癌3种放疗技术心脏和肺的剂量分布。方法 搜集2015年1月至2016年2月在浙江省肿瘤医院接受治疗的15例胸中下段食管鳞癌患者资料。患者均接受胸部放射治疗，每位患者共制作3套放疗计划。调强放疗（IMRT）和容积旋转调强放疗（VMAT）在RayStation 4.0v系统制作，螺旋断层放疗（TOMO）在TomoHTM Version 2.0.5系统制作。处方剂量60 Gy/30次。比较计划体积（PTV）、心脏、心脏亚单位以及肺剂量参数。结果 PTV、心脏和肺的平均体积为（399±355）、（671±274）和（3 907±1 717） cm3。与IMRT和VMAT相比，TOMO可以降低PTV、心脏、左心房及肺的最大剂量（H=10.889、7.433、12.080、11.401，P〈0.05）。3种放疗技术的适形指数和均匀性指数差异无统计学意义（P〉0.05）。结论 相较于IMRT和VMAT，TOMO可以降低PTV、心脏、左心房和肺的最大剂量，但均匀性及适形性差异无统计学意义。放疗过程中心脏与肺存在相互影响，TOMO技术可能带来的临床优势尚待进一步研究证实。

Objective To compare the dosimetric differences in heart and lung among three radiotherapy techniques in the treatment of thoracic esophageal cancer. Methods A total of 15 thoracic esophageal cancer patients treated in Zhejiang Cancer Hospital during the period of January 2015 to February 2016 were enrolled in this retrospective dosimetric study. Three radiotherapy treatment plans, including intensity-modulated radiotherapy （IMRT）, volumetric intensity modulated arc therapy （VMAT） with Raystation 4.0v TPS, and tomotherapy （TOMO） plans with TomoTTM v2.0.5 TPS were generated for each patient with a prescribed dose of 60 Gy at 2 Gy per fraction. Dosimetric differences in planning target volume （PTV）, heart, cardiac subunits and lung were compared. Results The mean volumes of PTV, heart and lung were （399±355）, （671±274） and （3 907±1 717）cm3, respectively. Compared with VMAT and IMRT, TOMO reduced the maximum dose of PTV, heart, left atrium and lung （H=10.889, 7.433, 12.080, 11.401, P〈0.05）. No difference was observed in conformity or homogeneity among these three plans. Conclusions TOMO reduced the maximum dose to PTV, heart, left atrium and lung compared with VMAT and IMRT, However, no difference in conformity and homogeneity was observed. The impact of dosimetric advantage of TOMO needs further verification due to the interaction between heart and lung for thoracic esophageal cancer patients.