摘要
背景与目的:放疗过程中,肿瘤退缩会造成其空间位置改变.进而可能影响肿瘤内放疗剌最分布。本研究探讨NSCLC放疗过程中肿瘤退缩对计划靶体积(TPV)和肿瘤周围关键器官剂量分布的影响.方法:选择从2003年1月-2005年12月,在我院接受根治性放疗的NSCLC患者10例。所有患者均行定位CT扫描,制定三维适形放疗计划,在放疗开始约4周后,大体肿瘤体积(GTV)剂量达到40—50Gy时,行第2次定位CT扫描,两次定位CT扫描,患者采用相同固定装置、保持相同体位。回顺性分析这些患者的定位CT:根据首次定位CT制定三维适形放疗计划Plan1,处方剂量为64Gy/32次;根据第2次定位CT制定的三维适形放疗计划Plan2,处方剂量为24Gy/12次;将Plan1的处方剂量更改为40Gy/20次.之后与Plan2叠加,形成计划Plan3,Plan3用于模拟开始放疗时采用Plan1.当GTV剂量达40Gy后,采用根据退缩后肿瘤制定的放疗计划Plan2完成冶疗、比较两次定位CT上GTV的体积;以D95(95%PTV体积接受的剂量)、D99和V100%(接受处方剂量的PTV体积所占的百分比)为参数,比较采用Plan1时,PTV1(根据首次定位CT确定的计划靶体积)和PTV2(根据第2次定位CT确定的计划靶体积)的剂量分布差异;以双肺(减去PTV的体积)接受大于20Gy照射的体积(V20)、甲均剂量(MLD),脊髓的最大剂量(Dmax)、1cm^3脊髓受到的剂量(D1cm^3),心脏的平均剂量(MHD),食管接受大于55Gy照射的体积(V55)、平均剂量(MED)为参数,比较采用Plan1与采用Plan3时肿瘤周围关键器官的剂量分布差异。资料采用配对t检验.结果:GTV剂量达到39.6~52.5Gy后,GTV体积绝对缩小量的中位值为:9.5cm^3(1.7~64.4cm^3),GTV体积相对缩小量的中位值为:22.35%(10.05%~54.81%),与放疗前相比,GTV的体积差异具有最菩性(P=0.015),、采用Plan1,PTV1与PTV2的剂量分布差异无显著性。Plan1与Plan3相比,正常肺组织、脊髓和食管的剂量分布差异无显著性;心脏接受的剂量在采用Plan3时减小(P=0.023).结论:NSCLC放疗过程中肿瘤退缩对PTV剂量分布未产生具有统计学显著性的影响.但是,根据退缩后的肿瘤重新制定放疗计划可以减少肿瘤周围关键器官接受的剂量,尤其是可以减少心脏接受的剂量。
Background and purpose: The dose distribution of tumor may be affected by geometrical changes due to tumor shrinkage during 3-DCRT for non-small cell lung cancer ( NSCLC). In this study, we evaluated the effect of tumor regression during treatment on the dose distribution of 3D-CRT fnr non-small cell lung cancer. Methods: Ten NSCLC patients, who received 3D-CRT in our hospital between Jan 2003 and Dec 2005, were entered into this study. All patients underwent simulation CT scans before radiotherapy and once during radiotherapy, after about 40 Gy. Target vohunes and critical organs were delineated on both CT scans. The gross tumor volumes of two CT scans were compared. Treatment plans, plan 1 and plan 2, were generated based on the two simulation CT scans, respectively. To evaluate the impact of tumor regression, the dose distribution of PTVI and PTV2 were compared when Plan 1 was used, and V20 of lung, mean lung dose (MLD), Dmax of spinal cord, D1cm^3 of spinal cord, mean heart dose(MHD), V55 of esophagus,mean esophagus dose (MED) were selected as the end points to compare the dose distribution of normal tissues when plan I was used with plan 3( the hybrid plan of plan 1 and plan 2) . Paired-samples t test was used for statistics. Results: The median absolute loss of the GTV was 9.5cm^3(1. 7-64.4 cm^3) after about 40 Gy radiotherapy, and the median relative loss of GTV was 22.35 % ( 10.05 % -54.81% ). The difference of GTV before treatment and after about 40 Gy radiotherapy have statistical significance( P =0.015). The dose distribution of PTV was not changed after about 40 Gy external beam radiotherapy, but a modified plan that was based on the intratreatment CT image could significantly diminish the treated heart volume. Conclusions: The conformal radiation therapy plan, based on the first simulation CT scan, still had good tumor coverage after about 40 Gy external beam radiotherapy despite the tumor regression. Replanning can significantly diminish the dose to the heart.
出处
《中国癌症杂志》
CAS
CSCD
2007年第4期329-332,共4页
China Oncology
关键词
肺肿瘤
非小细胞肺癌
放射疗法
肿瘤退缩
lung neoplasm
non-small cell lung cancer
radiation therapy
tumor regression