PET/CT下非小细胞肺癌三维适形放疗中肿瘤退缩及对治疗计划参数的影响

目的:观察PET/CT下非小细胞肺癌(NSCLC)三维适形放疗(3D-CRT)中肿瘤退缩对靶区周围危及器官治疗计划参数的影响.方法:分析在PET/CT定位下行根治性3D-CRT的NSCLC患者55例,根据PET/CT融合图像勾画初始肿瘤放疗靶区,给予根治剂量处方量60~66 Gy/30~33 f 制定3D-CRT计划;放疗20次40 Gy时根据肿瘤退缩情况重新CT定位勾画靶区,修改照射野后重新制定放疗计划完成治疗.比较两次定位影像上GTV的体积VGTV(cm3)、PTV的体积VPTV(cm3) 差异;并对初始放疗计划和实际完成的计划靶区周围危及器官的剂量分布进行比较.结果:55例NSCLC患者中,除1例GTV体积增大(1.77cm3,4%)外,其余54例GTV体积均有不同程度缩小(6%~67%),差异有统计学意义(t=6.635,P=0.000).相应的,除1例PTV体积增大(17.13cm3,8%)外,其余54例PTV体积均有不同程度缩小(3%~59%),差异有统计学意义(t=8.045,P=0.000).两种计划参数VGTV、VPTV、VL20、VR20、SCM、MSD、MLD、MRD、MHD、ESM差异有统计学意义(P=0.000、0.000、0.000、0.000、0.001、0.000、0.000、0.000、0.002、0.031).结论:在NSCLC放疗过程中,肿瘤体积发生明显变化,而根据肿瘤退缩情况适时缩野、重新制定放疗计划,可显著降低肺及脊髓的受照射剂量,为提高靶区剂量、优化放疗计划提供了可能.

The impact of tumor regression on the threedimensional conformal radiotherapy treatment planning of non-small cell lung cancer based on PET/CT

Objective:To investigate the impact of tumor regression on the three-dimensional conformal radiotherapy(3D-CRT) treatment planning of non-small cell lung cancer(NSCLC) when using PET/CT-based target volume delineation and treatment management.Methods:PET/CT scanning was performed in 55 pathologically proven NSCLC patients for radical radiotherapy.The initial radiotherapy protocol was designed to deliver a prescribed dose of 60~66 Gy in 30~33 fractions to the PTV.After receiving a total dose of 40 Gy/20 fractions in four weeks,the target volume was again contoured on the basis of the new CT data set according to indications of tumor regression.The rest radiotherapy management was completed based on the new 3D-CRT plan.From the dose volume histograms and dosed distributions on each plan,the dosimetric factors were analyzed and compared.Results:The difference of volume of GTV(pulmonary gross tumor volume,VGTV)and PTV(planning target volume,VPTV)were statistically significant(t=6.635,8.045,P=0.000,0.000)between pre-radiotherapy and mid-radiotherapy(40 Gy/20 fraction),while 54 with the reduction of GTV(6%~67%) and PTV(3%~59%),and only 1 with the enlargement respectively.Between the initial radiotherapy planning and actually completed one,the differences of volume of GTV,PTV and dosimetric parameters including VGTV,VPTV,VL20,VR20,SCM,MSD,MLD,MRD,MHD,ESM were statistically significant(P=0.000,0.000,0.000,0.000,0.001,0.000,0.000,0.000,0.002,0.031).Conclusion:There were significant alterations in the GTV and PTV seen on repeat CT scans during radiotherapy.Furthermore,in corporation of the second repeat scan data in the RT planning the radiation exposure of the esophagus and spinal cord was reduced,and thus allowed minimizing the dose to normal structures and more safely made the dose increases directed at the target.