非小细胞肺癌多发脑转移射波刀放疗的不同计划设计方案分析

Dosimetric comparison of two radiotherapy treatment planning approaches for multiple brain metastases from non-small cell lung cancer on CyberKnife

目的对比分析采用射波刀(CyberKnife)立体定向放射治疗多发脑转移的非小细胞肺癌患者时,不同计划设计方式对颅内剂量分布的影响。方法选取天津医科大学肿瘤医院CyberKnife中心2017年12月至2018年12月期间收治的20例多发脑转移非小细胞肺癌患者进行回顾性分析,对每例患者分别选择单靶区多计划和多靶区单计划进行治疗计划设计。通过对计划靶区(PTV)及其周围正常脑组织、危及器官(OARs)的剂量和适形指数(CI)、实施治疗总节点数和总机器跳数(MUs)对比分析,进行两种物理计划设计方案评价。结果采用两种设计方式所得治疗计划均能够满足>95%PTV接受处方剂量照射。多靶区单计划方式能够明显降低患者PTV周围正常脑组织受照最高剂量和平均剂量,使得脑干受照最高剂量和平均剂量分别相对下降1.62%和5.57%(t=1.09,P<0.01),治疗总照射节点数和总机器跳数平均相对下降了4.63%(t=1.87,P<0.01)和1.06%,缩短临床治疗时间。两种方式设计所得治疗计划的CI指数未见明显差异。结论CyberKnife能够实现对非小细胞肺癌多发脑转移患者的精准立体定向放疗,在进行放射治疗计划设计时,将直径及体积相近的多靶区单计划设计,不仅能够减小患者正常脑组织及OAR的受照剂量,而且能够缩短治疗时间,提高治疗效率。

Objective To compare the dosimetrics of the plan target volume(PTV)and organs at risk(OARs)between two treatment planning approaches for patients with multiple brain metastases from non-small cell lung cancer on CyberKnife.Methods 20 patients with multiple metastases from lung carcinoma were reviewed and analyzed,who had been treated by CyberKnife from December 2017 to December 2018.The CyberKnife stereotactic radiotherapy plans of the 20 cases were re-planed with single plan for multiple lesions and multiple plans per lesion.The dosimetry differences of PTV and OARs isodose disribution,conformity index(CI),total beam counts and total monitor units(MUs)were compared in the two types of plans.Results The two types of plans could satisfy over 95%PTV coverage of the prescription dose.The maximum and mean dose of normal brain adjacent to the PTV were reduced in multiple plan approach effectively.Moreover,the maximum and mean dose of OARs(brainstem)dropped by 1.62%and 5.57%(t=1.09,P<0.01)respectively.The number of treatment nodes and total MU declined by 4.63%(t=1.87,P<0.01)and 1.06%in multiple plan approach,which could significantly shorten the clinical treatment time.The differences in CI index between these two types of plans was of no statistical significance.Conclusions For patients with multiple brain metastases of similar diameter and volume from non-small cell lung cancer to be treated on CyberKnife,multiple plans per lesion could not only reduce dose to normal brain tissue and OARs,but also improve the treatment efficiency.