胸上段食管癌调强放疗与适形放疗计划的剂量学比较

Dosimetric comparison between intensity-modulated radiotherapy and conformal radiotherapy for upper thoracic esophageal carcinoma

背景与目的:胸上段食管癌所处的解剖特点导致其放疗计划的制订难度很大,而调强放疗(intensity-modulated radiotherapy,IMRT)有可能克服上述难题。本研究比较分析IMRT和三维适形放疗(conformal radiotherapy,CRT)在胸上段食管癌的剂量学优劣,为IMRT在食管癌的临床应用提供参考。方法:选择胸上段食管癌11例进行研究。在实际治疗采用的CRT计划基础上,每一病例再设计一5野IMRT计划进行对比。对比内容包括相关靶区和危及器官的剂量体积直方图参数。结果:肿瘤及相邻组织的计划靶区可见IMRT和CRT计划之间的平均剂量、最大剂量、包含99%和95%靶区的剂量均很接近(P>0.05),但IMRT较CRT的适形指数好(0.68±0.04vs.0.46±0.11,P<0.01)。IMRT对锁骨上区的剂量均匀性较CRT更好,二者的非均匀指数分别为1.17±0.05和1.33±0.15(P=0.01)。IMRT计划中脊髓计划区的最高受量明显较CRT的低(44.4Gy vs.52.5Gy,P<0.05);10Gy以上的肺受照体积为(32±6)%,也明显较CRT计划的(35±9)%低(P<0.05)。结论:对胸上段食管癌,调强放疗较适形放疗有更好的剂量适形性,可更有效保护脊髓,并显著降低肺10Gy以上剂量的受照体积。

Background and Objective： Treatment planning for radiotherapy of upper thoracic esophageal carcinoma is challenging due to the anatomical features. The difficulty may be resolved by intensity-modulated radiotherapy （IMRT）. This study was to compare the dosimetric advantages of IMRT to that of conformal radiotherapy （CRT） for upper thoracic esophageal carcinoma, and to explore the clinical application of IMRT. Methods： Eleven patients with upper thoracic esophageal carcinoma were enrolled. In addition to the actually used CRT plan, a five-field IMRT plan was generated for each case. The parameters of dose volume histogram for targets and organs at risk were compared between two techniques. Results： For the planning target volume （PTV） of tumor and para-tumor tissues, the mean dose, maximal dose, doses covering 99% and 95% volume were similar in IMRT and CRT plans （P〉0.05）. However, IMRT plan had a higher conformity index than CRT plan （0.68±0.04 vs. 0.46±0.11, P〈0.01）. For the PTV of supraclavicular region, IMRT plan showed a better dose heterogeneity index than CRT plan （1.17±0.05 vs. 1.33±0.15, P=0.01）. IMRT plan had lower maximal dose to the planning risk volume of the spinal cord （44.4 Gy vs. 52.5 Gy, P〈0.05） and lower lung volume received dose of 10 Gy or higher [（32±6）% vs. （35±9）%, P〈0.05] than CRT plan. Conclusion. For the upper thoracic esophageal carcinoma, IMRT has more conformal distribution of dose and better spinal cord sparing than CRT, and can reduce the volume of lung that received dose of 10 Gy or higher.