Evaluation Of IMRT On Effcation And Prognosis Of Patients With Limited-stage Small Lung Cancer And Dosimetric Comparition Of VMAT And IMRT

Objectives 1 To study the volume change and its influencing factors of limited-stage small cell lung cancer?LS-SCLC?treated by intensity modulated radiation therapy?IMRT?,and to analyze the prognostic factors.2 To evaluate the safety of Volumetric-Modulated Arc Therapy?VMAT?technology by comparing the dose of VMAT with that of Intensity Modulated Radiation Therapy?IMRT?in normal tissues of limited-stage small cell lung cancer.Methods 1 A retrospective analysis was performed on 101 LS-SCLC of patients treated with IMRT in Tangshan People's Hospital from May 2016 to November 2017,and survival analysis was performed.The tumor volumes of 20 patients with regular review were calculated using the Treatment Planning System?TPS?before radiotherapy and at 1,2,4,6,9 and 12 months after radiotherapy,and the trend of volume change and its influencing factors were analyzed.2 The clinical data of 52 LS-SCLC of patients treated with IMRT in Tangshan People's Hospital from May 2016 to November 2017 were collected,The VMAT plan was designed again.The maximum dose of planning target volume?PTVDmax?,minimum dose of planning target volume?PTVDmin?,mean dose of planning target volume?PTVD mean?,conformity index?CI?,homogeneity index?HI?and irradiated volume of Organs at risk?OAR?were calculated and the results were analyzed by paired t-test.Results 1 Paired t-test was used to analyze the relative volume of tumor within one year after radiotherapy.The difference was statistically significant when radiotherapy was located vs.at the end of radiotherapy?P=0.014?,2 months vs.4 months?P=0.032?,6 months vs.9 months?P=0.027?.There was no statistical significance in the other groups,P>0.05.Chi-square test and logistic regression multivariate analysis showed that there were no influencing factors on tumor regression at the end of radiotherapy,P>0.05.The survival analysis found that age,lung diseases,radiation dose and tumor regression rate were the factors influencing survival?P=0.010,0.000,0.000,0.000?.Cox proportional risk model multivariate analysis found that age,basic pulmonary disease,radiation dose,tumor regression rate were the prognostic factors?P=0.013,0.004,0.035,0.031?.2 Mean lung dose?MLD?,lung V₂₀,lung V₃₀VMAT plan was smaller than IMRT plan,the difference was statistically significant?P=0.000,0.000,0.000?.The spinal cord Dmax and the heart Dmean,V₃₀,V₄₀,V₄₅,V₅₀,V₆₀,VMAT plans were smaller than those of IMRT plans,and the difference was statistically significant?P=0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.000,0.001?.PTV Dmax,PTV Dmean,HI and CI,VMAT plan were larger than IMRT plan,the difference was statistically significant?P=0.000,0.002,0.021,0.004?.PTV Dmin and MU,VMAT plans were smaller than IMRT plans,and the difference was statistically significant?P=0.000 and 0.000?.Lung V₅ VMAT plan was larger than IMRT plan,lung V10 VMAT plan was smaller than IMRT plan,there was no significant difference?P>0.05?.Conclusions 1 The volume of LS-SCLC tumors retreated most obviously at the end of IMRT,the smallest at the first month after radiotherapy,and then increased gradually.Six months after radiotherapy,the volume of LS-SCLC tumors retreated more significantly than that before radiotherapy;Age,basic pulmonary disease,dose of radiotherapy and tumor regression rate at the end of radiotherapy are the prognostic factors of LS-SCLC.2 LS-SCLC VMAT plan has better target conformity index,higher target dose,better protection of Organs at risk?OAR?,less machine unit,less unnecessary irradiation of normal tissues in the treatment area,and higher lung V₅ than IMRT plan.Figure 6;Table 12;Reference 120.