食管癌术后胸腔胃内复发肿瘤照射技术探讨

Study on radiation technique for recurrent tumor in thoracic stomach after resection of esophageal cancer

目的为了获得胸腔残胃肿瘤精确照射的适宜合理计划靶体积(PTV),进行了放疗中胸腔残胃位置移动的观察,目的是为确定三维适形放疗PTV的适宜范围。方法食管癌患者接受食管癌根治、食管胃主动脉弓上吻合手术后胸腔胃内肿瘤转移复发5例,通过CT定位结合反复X光下复核。以首次X线片上显示照射野中心为基点,在X线光片上测量“+”中心与Y轴和X轴方向胸腔胃壁的距离,并逐日记录探讨应用三维适形放疗技术治疗胸腔残胃内病灶的合理计划靶体积PTV范围。结果胸腔胃壁在X轴和Y轴方向的移动范围在机架15°时分别为±2.75mm和±2.58mm,在30°时分别为±2.61mm和±2.34mm,0°时分别为±3.78mm和±3.15mm,提示胸腔胃以上下和左右方向移动范围相对较大,而前后的移动范围相对较小。结论在临床观察中笔者发现由于患者进食规律的变化和其他因素的影响,胸腔残胃的位置常有比较明显的移动,这一点为PTV的确定带来一定的困难,特别是采用精确放疗技术时如果因器官移动造成靶区边缘的低剂量或遗漏,将导致肿瘤失控或者正常胃组织过量照射等严重后果。

Objective To study the measurement of the movement of residue thoracic stomach after surgical resection for esophageal cancer and define the optimal planning target volume （PTV）. Methods Five patients with recurrent esophageal cancer were treated with 3D conformal radiotherapy （3D-CRT）. Treatment planning was based on CT images taken at 5 mm intervals in patient performed localization. X-ray simulations were carried out every day since the first fraction of the radiotherapy. Patient localization was checked before each treatment session using both fluoroscopy and X-ray films. The distances of the stomach wall from the isoceter were measured. Results The thoracic stomach movement at axial Y and X is significantly larger at the gantry zero than 15 and 30 degree,the range were ± 2.75 mm and ± 2.58 mm at 15 degree; ± 2.61 mm and ± 2.34 mm at 30 degree. It demonstrated that at gantry 0° they were ± 3.78 mm and ± 3.15 mm,these data suggested the PTV should be larger, 10 mm might be optimal. Conclusion Recurrant esophageal cancers usually are surgically inoperable, 3D-CRT is an optimal treatment. Based on this study it is suggested that the PTV for these eases should be adjusted at 10 mm.