食管癌二次定位调整缩野调强放疗的剂量学研究

Dosimetric study of reducing IMRT field by secondary positioning adjustment in esophageal carcinoma

目的对食管癌调强放疗(IMRT)后程缩野照射计划与首程常规计划进行累及器官剂量学对比,初步探讨后程缩野照射的价值。方法 2015年9月至2016年10月,随机选取15例Ⅱ~Ⅲ期胸中上段食管癌患者并勾画两套靶区(后程缩野计划及首程常规计划)。大体肿瘤靶区(GTV)包括食管肿瘤病灶(GTV-t)和食管旁肿大淋巴结(GTV-nd)。临床靶区(CTV)-t轴向在GTV外扩6 mm,纵向包括GTV-t外30 mm;计划靶区(PTV)-t在各CTV-t基础上均匀外扩5 mm;PTV-ln=GTV-ln+10 mm;PTV=PTV-t+PTV-ln。首程:靶区设置如上。后程:在首程计划执行至40 Gy/20 f后,重新进行CT模拟定位,靶区设置为:GTV包括食管肿瘤病灶GTV-t和食管旁肿大淋巴结GTV-nd;内靶体积(IGTV)=GTV-t纵向外放30 mm,前后左右外放5 mm;IGTV-ln=GTVln+5 mm;补量完成计划C2-plan2;危及器官:勾画脊髓、心脏、肺。分析比较两种计划的靶区剂量及肺、脊髓、心脏等危及器官受量。结果两种放疗计划的剂量学比较:后程缩野计划在肺至少接受20 Gy照射的体积百分比(V20)、心脏V30及脊髓最高受量方面均小于首程常规计划(P均<0.01)。结论食管癌调强放疗后程缩野照射可减少危及器官放射剂量受量。

To analyze the dosimetry involved organs for late-course field reduction radiation planning of intensity modulated radiation therapy（ IMRT） in esophageal carcinoma and preliminarily explore the value of late-course field-reduction radiation. Methods A total of 15 patients with upper and middle thoracic esophageal carcinoma of stage Ⅱ-Ⅲ were randomly selected from September 2015 to October 2016,in whom two sets of target areas were drawn（ late-course field reduction plan and first-course conventional plan）. The gross tumor volume（ GTV） included esophageal tumor lesion（ GTV-t） and para-esophageal swollen lymph node（ GTV-nd）. Clinical target volume（ CTV）-t expanded 6 mm outside GTV-t in the axial direction and 30 mm in the longitudinal direction. Planning target volume（ PTV）-t evenly expanded outwards 5 mm on the basis of corresponding CTV-t,and PTV-ln = GTV-ln ＋ 10 mm; PTV = PTV-t ＋ PTV-ln. The target area setting in first-course was above. Late-course： CT simulation positioning was re-conducted after implementing to 40 Gy/20 f,and the target volume was re-set up：（ 1） GTV was same with conventional planning： GTV-t and GTV-nd;（ 2） internal gross tumor volume（ IGTV） ： IGTV-t expanded outwards 30 mm in the longitudinal direction and 5 mm in the directions of front,back,left and right on the basis of GTV-t; IGTV-ln = GTV-ln ＋ 5 mm. Thereafter,the radiation was boosted to complete C2-plan2. Involved organs including lung,spinal cord and heart were drawn,and the target doses of two plans and radiation amount of exposure to involved organs were compared. Results The maximum dose of lung V20,heart V30 and spinal cord in field reduction planning significantly decrease compared with conventional planning（ all P〈0. 01）.Conclusion The late-course field reduction radiation after first-course of IMRT in esophageal carcinoma can reduce the radiation dose of exposure to involved organs.