Risk Factors Of Radiation-induced Pneumonitis In Lung Cancer Treated With Volumetric Rotational Intensity Modulated Radiotherapy

Purpose:Through retrospective analysis of the general clinical data,treatment methods and dose-volume factors of lung cancer patients treated with volume-rotating intensity-modulated radiotherapy for the first time,to evaluate the incidence of radiation pneumonia(RP)after lung cancer treated with VMAT and to explore the risk factors of RP which was equal or greater than 2 grade(?grade 2).Method:All lung cancer patients who met the inclusion criteria were divided into two groups: RP<2 grade and RP?2 grade.The general clinical data(including sex,age,smoking history,histological type,tumor location,disease staging,forced expiratory volume in one second(FEV1),diabetes mellitus),treatment methods(including history of surgery,chemotherapy,and concurrent radiotherapy and chemotherapy before radiotherapy),dose-volume factors(including PCTV volume,average lung dose,V5,V10,V20,V30 of bilateral lung)and other clinical data were analyzed.The differences between continuous variables were compared by the Student's t-test and significant differences between the categorical variables were evaluated using the Chi square test.Risk factors with P < 0.05 were included in the binary logistic regression analysis.The receiver operating characteristic(ROC)curve was used to determine the high-risk threshold for the occurrence of RP?grade 2.When the P value was <0.05,the difference was statistically significant.Result:1.A total of 87 patients with lung cancer who met the inclusion criteria were enrolled in the study.The follow-up period began on the first day of radiotherapy and ended at least 6 months after the end of radiotherapy.29 patients of all included subjects developed during or after radiotherapy,with an incidence of 33.3%.And among them,10 patients(11.5%)were in RP of grade 1,15 patients(17.2%)were in RP of grade 2,3 patients(3.4%)were in RP of grade 3,and 1 patient(1.1%)was in RP of grade 5.No RP of grade 4 was found.2.Univariate analysis showed that FEV1 < 2L,combined with diabetes mellitus,V5,V10,V20,V30 of bilateral lung,and high average lung dose were significantly correlated with the occurrence of RP?grade 2(P < 0.05);While clinical characteristics including gender,age,smoking history,histological type,tumor location,disease staging were not significantly correlated with the occurrence of RP?grade 2.3.Multivariate analysis showed that V20,V30 of bilateral lung and high average lung dose were independent risk factors for RP?grade 2.4.ROC curve analysis showed that V20,V30 of both lungs and increased mean lung dose(MLD)had high predictive value for the occurrence of RP?grade 2.And the high-risk threshold values were 21.2%,11.9% and 1114 cGy,respectively.Conclusions:Combined with diabetes mellitus,low pre-RT pulmonary function(FEV1 < 2L),V5?V10?V20?V30 of bilateral lung and higher level of MLD were significantly correlated with the occurrence of RP?grade 2;V20,V30 and higher level of MLD were independent risk factors for RP?grade 2.