Analysis Of Factors Of Radiation Pneumonitis After Intensity Modulated Radiotherapy For Lung Cancer

Objective: To analyze the risk factors related to grade ?2 radiation pneumonitis(RP)after intensity modulated radiotherapy(IMRT)for lung cancer and provide evidence for clinical radiotherapy plan.Methods: From December 2014 to November 2017,a total of 251 patients with lung cancer treated with IMRT in Department of radiotherapy,the second affiliated Hospital of Dalian Medical University,including 148 males and 103 females,with a median age of 58 years old(33 to 81 years old)were analyzed retrospectively.There were 128 cases of non-small cell lung cancer(including 90 cases of adenocarcinoma and 38 cases of squamous cell carcinoma)and 123 cases of small cell lung cancer.There were 204 cases of central lung cancer and 47 cases of peripheral type,including115 cases of left lung and 136 cases of right lung.145 cases were located in upper lobe and 106 cases in middle lower lobe.A total of 109 patients received surgical treatment before radiotherapy,142 patients were not operated on.Date of 212 patients were treated with amifostine during radiotherapy,39 cases were not used.The clinical related factors(sex,age,diabetes,smoking history,basic lung diseases,pathological types,primary lobes,primary location,lung cancer classification,surgery,radiotherapy combined with chemotherapy,amifostine)were analyzed in 251 patients.At the same time,radiation physical dosimetry factors of 142 patients without surgery(mean lung dose,the number of ejection fields and V5,V10,V20 and V30 of the affected lung,the normal lung,the bilateral lung)were analyzed.Chi-square test(?2)and independent sample t-test(t-test)were used to analyze the high risk factors which had statistical difference with those of grade ?2 RP.The independent factors affecting the occurrence of grade ?2 RP were obtained by using Binary Logistic regression model.Finally,for high risk factors affecting the incidence of grade ?2 RP in radiophysical factors,the optimal critical value of high risk factors was obtained by using receiver operatorcharacteristic curve(ROC curve).Results: 1.In this study,the incidence of grade ?2 RP was 26.29(66/251),of which there were 48 cases of grade 2 RP(19.12%),16 cases of grade 3 RP(6.37%),and 2cases of grade 4 RP(0.80%)respectively.In univariate analysis,among the clinical related factors,sex(?2=7.010,P=0.008),age(?2=20.011,P=0.000),diabetes(?2=4.655,P=0.001),smoking history(?2=4.846,P=0.028),basic lung diseases(?2=12.082,P=0.001),primary lobes(?2=4.281,P=0.039)were all risk factors of grade ?2 RP.In the course of radiotherapy,among 212 patients with amifostine,47 patients had grade?2 RP and 19 cases had grade ?2 RP in 39 patients without amifostine,the difference is statistically significant(?2=11.979,P=0.001).2.In multivariate analysis,binary logistic regression model showed that age(P=0.000),basic lung disease(P=0.004),primary pulmonary lobe(P=0.040)and amifostine(P=0.001))were independent factors influencing the development of grade?2 RP.3.Among the factors associated with radiophysics in patients without surgery,mean lung dose(t=12.831,P=0.000),affected lung V5(t=4.859,P=0.000),affected lung V10(t=2.363,P=0.021),healthy lung V20(t=2.494,P=0.015),bilateral lung V5(t=4.887,P=0.000),bilateral lung V10(t=3.616,P=0.000),bilateral lung V20(t=2.171,P=0.032),bilateral lung V30(t=3.167,P=0.002)were all correlated with the incidence of grade ?2 RP.4.In multivariate analysis,binary logistic regression analysis showed that mean lung dose(P=0.000),affected lung V5(P=0.006),normal lung V20(P=0.004)and bilateral lung V5(P=0.021)were independent factors affecting the occurrence of grade? 2 RP.In our study,there was no significant difference between the pathological type,primary location,lung cancer classification,operation,radiotherapy combined with chemotherapy,affected lung V20,affected lung V30,normal lung V5,normal lung V10,normal lung V30 and the incidence of grade ?2 RP.5.By using the ROC curve,the optimum critical values of the physical factors related to the occurrence of grade ? 2 RP are 14.54 Gy(AUC=0.927,P=0.000),65.53%(AUC=0.691,P=0.000),64.44%(AUC=0.609,P=0.008),10.49%(AUC=0.619,P=0.004),55.26%(AUC=0.753,P=0.000),36.69%(AUC=0.655,P=0.000),24.46%(AUC=0.613,P=0.007),15.72%(AUC=0.638,P=0.001)respectively.Conclusion: 1.Male,age ? 60 years old,diabetes,smoking history,combined with basic lung diseases,and lesions located in the middle or lower lobes were the risk factors of grade ?2 RP.2.The incidence of grade ?2 RP can be reduced by using amifostine during intensity modulated radiotherapy in patients with lung cancer.3.Mean lung dose,affected lung V5,affected lung V10,normal lung V20 and bilateral lung V5,bilateral lung V10,bilateral lung V20,bilateral lung V30 were high risk factors for grade ?2 RP.4.Age ? 60 years old,complicated with basic lung disease,lesion located in middle or lower lobes,amphostatin,mean lung dose,affected lung V5,normal lung V20 and bilateral lung V5 were independent influencing factors of grade ?2 RP.5.In order to reduce the risk of RP,for the patients with the above clinical high risk factors,the physical indexes associated with grade ?2 RP in the radiotherapy plan should be strictly restricted,especially the values of MLD and bilateral lung V5 should be lower than 14.54 Gy,55.26%,respectively.