非小细胞肺癌同层双转移病灶SBRT-VMAT计划设计方式研究

Research on SBRT-VMAT plans for non-small cell lung cancer with unilateral ipsilateral double metastatic lesions

目的:研究非小细胞肺癌同层双转移病灶立体定向放射治疗(stereotactic body radiation therapy,SBRT)时不同计划方式对肺的受量、机器跳数、适形性指数(conformity index,CI)及剂量梯度(gradient index,GI)的影响,以为此类患者治疗计划的设计提供参考。方法:选取非小细胞肺癌单侧同层双转移病灶患者共11例,采用容积旋转调强放疗(volumetric modulated arc therapy,VMAT)技术制订3种SBRT计划。根据4D-CT定位方式的最大投影图像勾画内靶区ITV1、ITV2,均匀外放3 mm得到计划靶区PTV1、PTV2,并将PTV1与PTV2相加得到PTV12。第1种计划方式以PTV1和PTV2靶区中心为治疗中心,制订2个单独计划plan-1与plan-2,合并为plan-sum后进行剂量评估;第2种计划方式分别以PTV1和PTV2中心为治疗中心,制订多中心的计划plan-D。第3种计划方式以PTV12的中心为治疗中心,制订单中心计划plan-S。将plan-sum的plan-1与plan-2分别归一到PTV1和PTV2 95%体积以满足处方剂量,将plan-S与plan-D归一到PTV12 95%体积以满足处方剂量。比较3种计划方式下肺的受量、机器跳数、CI及GI。采用SPSS 25.0软件进行统计学分析。结果:plan-S除V_(5)与plan-sum相比差异无统计学意义(P>0.05)外,V_(10)、V_(20)、V_(30)及平均剂量均低于plan-sum,差异有统计学意义(P<0.05);plan-D肺的受量和平均剂量均低于plan-sum,差异有统计学意义(P<0.05);plan-S与plan-D计划方式下肺的受量差异无统计学意义(P>0.05)。plan-sum的CI低于plan-S和plan-D,差异有统计学意义(P<0.05);plan-S与plan-D的CI差异无统计学意义(P>0.05)。plan-D的GI低于plan-S和plan-sum,差异有统计学意义(P<0.05);plan-S与plan-sum的GI差异无统计学意义(P>0.05)。plan-D和plan-sum的机器跳数高于plan-S,差异有统计学意义(P<0.05);plan-D与plan-sum的机器跳数差异无统计学意义(P>0.05)。结论:若患者身体状况支持长时间保持定位姿势,可以采用多中心的计划方式优化剂量分布和提高适形度;若患者身体状况较差,可以采用单中心的计划方式缩短治疗时间。

Objective To study the effects of different SBRT-VMAT plans for non-small cell lung cancer(NSCLC)with unilateral ipsilateral double metastatic lesions on received dose,monitor unit(MU),conformity index(CI)and gradient index(GI)of the lung,so as to provide references for therapy planning of the patient above.Methods A total of 11 NSCLC patients with unilateral ipsilateral double metastatic lesions were selected,with three plans developed for each patient by the volumetric modulated arc therapy(VMAT).The inner target areas ITV1 and ITV2 were contoured based on the maximum projection image of the 4D-CT localization mode,which were uniformly expanded externally by 3 mm to obtain the plan target area PTV1 and PTV2,and then PTV1 was added with PTV2 to get PTV12.The first planning mode had the centers of PTV1 and PTV2 target areas as the treatment centers,and two separate plans of plan-1 and plan-2 were developed and then combined into a plan-sum plan for dose evaluation;the second planning mode had the centers of PTV1 and PTV2 target areas as the treatment center,resepctively,and a multicenter plan(plan-D)was formed.The third planning mode had the center of PTV12 target area as the treatment center,and a single-center plan(plan-S)was designed.To meet the requirements of prescribed dose,plan-1 and plan-2 of plan-sum were normalized to PTV1 and PTV295%volume and plan-S and plan-D were normalized to PTV1295%volume.The three planning modes were compared in terms of received dose,MU,CI and GI of the lung.SPSS 25.0 software was carried out for statistical analysis.Results Plan-S had no significant differences with Plan-sum except V5(P>0.05),whose V10,V20,V30 and mean dose were significantly lower than those of plan-sum(P<0.05);plan-D had its received dose and mean dose statistically lower than those of plan-sum(P<0.05);plan-S and plan-D had no obvious differences in received dose of the lung(P>0.05).Plan-sum had the CI significantly lower than those of plan-S and plan-D(P<0.05);plan-S and plan-D had no statistically differences in CI(P>0.05).Plan-D had the GI significantly lower than plan-S and plan-sum(P<0.05).Plan-S and plan-sum had no significant differences in GI(P>0.05).Plan-D and plan-sum had no statistical differences in MU(P>0.05),which had the MUs significantly higher than that of plan-S(P<0.05).Conclusion A multicenter planning mode may be used for optimizing dose distribution and enhancing conformity in case the patient can tolerate prolonged immobilization in a fixed position,and a singlecenter planning mode should be adopted to shorten treatment time when the patient is in poor physical conditions.