非小细胞肺癌三维适形放疗中二次定位缩野对肿瘤靶区及肺受照射剂量的影响

THE IMPACT OF REDUCING-FIELD OF SECONDARY POSITIONING ON THE TUMOR TARGET VOL-UME AND RADIATION DOSE OF LUNG TISSUE OF THREE-DIMENSIONAL CONFORMAL RADIO-THERAPY FOR NON-SMALL CELL LUNG CANCER

目的探讨非小细胞肺癌三维适形放疗中二次定位缩野对肿瘤靶区及肺组织受照射剂量体积的影响。方法36例非小细胞肺癌患者，初次行CT定位扫描，制定三维适形放疗计划（Plan1），放疗至DT50～60Gy行第二次CT定位扫描，重新制定三维适形放疗计划（Plan2）。将Plan1、Plan2的肺Vdose参数加权求和，得到患者实施的Vdose参数（Plan3）。比较Plan1和Plan2、Plan1和Plan3 Vdose参数。结果Plan2 GTV和放疗前Plan1 GTV比较，绝对缩小量的中位数为96．97cm^3，相对缩小量的中位数为31．27％，差异有统计学意义（Z=-2．073，P=0．038）。Plan1和Plan2，Plan1和Plan3的Vdose参数差异均具有统计学意义（P〈0．05）。结论非小细胞肺癌放疗过程中可出现肿瘤缩小，行二次CT定位后依据缩小后的肿瘤体积重新制定三维适形放疗计划可减少肺受照射剂量体积。

Objective To explore the impact of reducing- field of secondary positioning on the tumor target volume and radiation dose of lung tissue of three- dimensional conformal radiotherapy for non- small cell lung cancer. Methods Totally 36 patients with non- small cell lung cancer were underwent simulation CT scans before radiotherapy and three- dimensional eonformal radiotherapy plan were formulated （Plan1）. After DT 50-60Gy, patients were underwent the second simulation CT scans and the new plan were formulated （Plan2）. To generate Plan3 through the weighted summation of Plan1 and Plan2 lung Vdose parameters. Planl Vdose parameters were compared with Plan2 and Plan3. Results To compare Plan1 and Plan2, the median of absolute reduced value of GTV was 96.97 cubic centimeters, the median of relative reduced value of GTV was 31.27%. There was statistically significant differences between Planl and Plan2 （Z = - 2. 073, P = 0. 038）. There was statistically significant differences on Vdose parameters of Planl and Plan2, Planl and Plan3 （P〈0.05）. Conclusions Tumor regression can be occured in the three- dimensional conformal radiotherapy on non- small cell lung cancer. Reducing- field of secondary positioning can reduce pulmonary irradiated dose volume.