基于卷积运算构建循环淋巴细胞在肺癌CRT和SBRT中差异模型

Modelling the difference of circulating lymphocytes between conventional fractionation radiotherapy and stereotactic body radiation therapy for lung cancer based on convolution operation

目的比较和验证常规分割放疗(CRT)和体部立体定向放疗(SBRT)在肺癌治疗中的差异。方法基于卷积运算和有限元法构建模型,模拟放疗中传递到循环淋巴细胞(CL)的放射剂量。选取3例肺癌患者进行模型模拟,临床CRT(10例次)和SBRT(10例次)进行验证。比较两种方式下CL累积剂量峰值(PCDC)差异,分析不同治疗时间、计划靶区(PTV)对CL累积剂量的影响,并验证临床CL变化规律。结果模拟集3例患者PTV分别为38、63、114 cm^(3),CRT的PCDC分别是1.26、1.79、2.54 Gy,SBRT的PCDC分别是0.84、1.22、1.55 Gy;同样PTV中,SBRT分别减少了0.42、0.57、0.99 Gy。验证集中,CRT和SBRT的CL变化值分别是(1.10±0.64)×10^(9)/L和(0.42±0.48)×10^(9)/L,差异有统计学意义(P=0.015);CRT和SBRT组PCDC分别是3.56(2.79,3.82)Gy和1.24(0.697,1.73)Gy,差异有统计学意义(P<0.001);CL变化值与PCDC呈正显著相关(r=0.455,P<0.05)。结论SBRT比CRT的PCDC、CL变化值更小;且随着PTV的增大,两者的PCDC差异可能越明显;CRT和越大的PTV可能对机体免疫功能产生越大的影响。

Objective To evaluate the difference between conventional fractionation radiotherapy(CRT)and stereotactic body radiation therapy(SBRT)in lung cancer.Methods A model was constructed based on convolution operation and finite element method,simulating the dose delivered to circulating lymphocytes(CL)in radiotherapy.The model was trained on a training group(n=3)and validated in an independent validation group between SBRT(n=10)and CRT(n=10).The peak cumulative dose of circulating lymphocyte(PCDC)was compared between the two schemes,and the effect of different PTV volumes and treatment time on the cumulative dose was also analyzed.The correlation between PCDC and CL change value was discussed.Results In the training group,PCDC with CRT to CL were 1.26 Gy,1.79 Gy,2.54 Gy in PTV of 38 cm^(3),63 cm^(3) and 114 cm^(3),and PCDC with SBRT to CL were 0.84 Gy,1.22 Gy,1.55 Gy in PTV of 38 cm^(3),63 cm^(3),114 cm^(3),respectively.PCDC gap of SBRT to CL was decreased by 0.42 Gy,0.57 Gy,0.99 Gy,respectively.In the validation group,the lymphocyte change value in SBRT and CRT were(1.10±0.64)×10^(9)/L and(0.42±0.48)×10^(9)/L,and there was significant difference(P=0.015).PCDC in SBRT and CRT were 3.56(2.79,3.82)Gy and 1.24(0.697,1.73)Gy,and there was significant difference(P<0.001).There was a positive correlation between lymphocyte change value and PCDC(r=0.455,P<0.05).Conclusions SBRT,compared to CRT,will lead to lower PCDC and CL lymphocyte change value,which may cause a greater impact on the difference of PCDC along with the enlargement of PTV.CRT and large PTV volume may cause more significant effect upon the body immune function.