非小细胞肺癌肿瘤体积大小对调强放射治疗肺剂量体积参数的影响

摘要

目的:探索非小细胞肺癌(non-small cell lung cancer,NSCLC)肿瘤体积大小对调强放射治疗(intensity modulated radiation therapy,IMRT)肺剂量学参数的影响,为制定IMRT计划时限定肺剂量参数提供参考依据.方法:回顾性分析2009年6月至2013年10月行IMRT的NSCLC共204例,将原发灶的计划靶区(planning target volume,PTV)处方剂量设定为60～66 Gy(2.00～2.25 Gy/次,共27～33次).分析正常肺组织接受放射剂量高于S或20 Gy照射的体积百分比(fractional volume percent of the lung receiving a dose＞S or 20 Gy,V5,V20)、正常肺组织接受放射剂量低于5 Gy的绝对体积(absolute volume of lung spared from receiving a dose＜5 Gy,AVS5)、平均肺剂量(mean lung dose,MLD),并采用回归模型进行曲线拟合来分析它们随原发灶肿瘤体积大小的变化所呈现的变化规律.结果:V5,V20和MLD随肿瘤体积的变化呈二次方程的曲线变化规律,而AVS5呈对数方程曲线变化规律.当肿瘤体积分别低于某一数值(依次为294.6,283.2,304.9 cm3)时,肺v5,V20和MLD随肿瘤体积增大而呈二次曲线性增大;而当肿瘤体积分别高于某一数值(依次为294.6,283.2,304.9 cm3)时,肺V5,V20和MLD随肿瘤体积增大而呈二次曲线性下降.肺AVS5随肿瘤体积的增大呈对数曲线下降.结论:随着肺肿瘤体积的的不断增大,V5,V20和MLD和AVS5的变化规律有所不同;当肿瘤体积超过一定界值(大约为300 cm3时,相对应的肿瘤直径为7～8 cm)后,制定NSCLC调强放射治疗计划时除关注肺V5,V20和MLD外,还应更加重视AVS5的限制.%Objective:To explore the effectof tumor volume on pulmonary dose-volume parameters by intensity-modulated radiation therapy (IMRT) in non-small cell lung cancer (NSCLC),and to provide a basis for pulmonary dose parameters in IMRT treatment.Methods:A total of 204 patients with NSCLC received IMRT were retrospectively analyzed from June,2009 to October,2013.The prescribed dose of planning target volume (PTV) for primary tumor was 60-66Gy (2.00-2.25 Gy,27-33 times in all).The fractional volume percent of the lung received a dose ＞5 or 20 Gy (V5,V20),and absolute volume of lung received a dose ＜5 Gy (AVS5).The mean lung dose (MLD) in normal tissues were analyzed.Regression model curve was used to analyze them along with the change of primary tumor volume.Results:With the increase in lung tumor volume,the V5,V20 and MLD presented quadratic equation curve,and AVS5 presented logarithmic equation.When the tumor volume,less than a certain value (294.6,283.2,304.9 cm3,respectively),the V5,V20 and MLD increased with tumor size and presented an increased quadratic curve;when the tumor volume was higher than a certain value (294.6,283.2,304.9 cm3 respectively),the V5,V20 and MLD was declined.The AVS5 was declined in a logarithmic curve along with the increase of tumor volume.Conclusion:With the increase in lung tumor volume,the change in rule ofV5,V20,MLD and AVS5 is not completely equivalent.When the tumor volume exceeds a certain boundary value (about 300 cubic centimeter),the corresponding tumor diameter is about 7-8 cm.In addition to the focus on pulmonary V5,V20 and MLD,we should also pay more attention to AVS5 restrictions in establishment ofIMRT in NSCLC.