The Correlation Between Radiation Dose To The Contralateral Hilum And Radiation Pneumonitis In Radiotherapy For Lung Cancer

Research Objectives:For lung cancer patients who have received radiotherapy,the contralateral hilum area was outlined in the radiotherapy plan,and the exposure dose was evaluated in the dose volume histogram of the radiotherapy plan.combination with the occurrence of symptomatic radiation pneumonitis in patients during the observation period,this paper discussed whether the exposure dose in the contralateral hilum region could predict the occurrence of symptomatic radiation pneumonitis,and if so,the dose volume factor of contralateral hilum and the corresponding critical value of each factor could be determined.Materials and Methods:Data of patients with lung cancer of different stages admitted to our hospital from January 2015 to December 2018 were collected,and lung cancer patients meeting the study requirements were finally included according to specific exclusion criteria.Meanwhile,general clinical data of the patients,whether radiation pneumonitis occurred and its degree were recorded(CTCAE V4.0 standard).In the completed radiotherapy plan for lung cancer patients,the contralateral hilum was outlined,and the hilum area was defined as the area surrounded by the bronchi above the segmental bronchial opening and the accompanying pulmonary vessels.After the drawing,the relevant dose volume parameters of the hilum region were recorded,including the volume of the contralateral hilum,the maximum dose(Dmax),the mean dose(Dmean),V10,V20,V30,V40,V50,V55,V60,D1cc,D2cc,D3cc and D5cc received.Lung V20 and Mean Lung Dose(MLD)were recorded.Subsequently,the patients were divided into two groups:radiation pneumonitis group(?grade 2)and no-radiation pneumonitis group.Regression analysis was used to screen the dose volume parameters,and the dose volume factors related to the occurrence of symptomatic radiation pneumonitis were obtained.If the regression analysis fails to screen out the factors related to the occurrence of RP,T test or non-parametric test is used to compare the differences between the two groups for screening.The ROC(Receiver Operating Characteristic)curve of the selected factors related to the occurrence of symptomatic RP was drawn to judge the prediction ability and calculate the prediction threshold.For the factors related to symptomatic RP with defined critical value,patients were divided into<critical value and?critical value according to the critical value,and the incidence of symptomatic RP was compared between the two groups.In addition,due to the anatomical location and the implementation of the actual radiotherapy plan of central lung cancer and peripheral lung cancer,the dose difference of the contralateral hilar is very large,so the volume factor of the hilar dose of central lung cancer and peripheral lung cancer will be analyzed statistically.P<0.05 was considered statistically significant.Result:1.215 patients with primary lung cancer were included in this study,and the results were consistent with many studies.The results of V20 and MLD in the whole lung were significantly higher in the symptomatic radiation pneumonitis group than in the non-radiation pneumonitis group(P<0.05).2.Among the relevant dose volume factors in the contralateral hilum region of peripheral lung cancer,except the contralateral hilum volume showed significant statistical difference in the two groups,the other dose volume factors showed no statistical difference in the two groups(P>0.05).ROC Curve showed that the volume of contralateral hilum had a certain degree of significance in predicting symptomatic pneumonitis,and the AUC(Area Under Curve)of contralateral hilum volume was0.669.3.Among the dose volume factors in the contralateral hilar region of central lung cancer,the mean dose,V20,V30,V40,V50 and d1cc-d5cc of hilum were higher in the radiation pneumonitis group than in the non-radiation pneumonitis group(P<0.05).Although the ROC curve showed that the above positive dose volume factors all had different degrees of predictive value for symptomatic radiation pneumonitis,the AUC of V30 and V40 of the contralateral hilum was greater than 0.7,showing a higher degree of predictive value,with AUC of 0.702 and 0.704,respectively.4.According to the ROC curve,the critical value corresponding to each factor and the incidence of symptomatic RP grouped by the critical value were obtained.The incidence of symptomatic radiation pneumonitis was 45.5%in the group of peripheral lung cancer with portal volume?49.9cm~3,and 19.4%in the group with portal volume?49.9cm~3.The incidence of symptomatic radiation pneumonitis in the control group was61%and 68.8%,respectively.The incidence of symptomatic radiation pneumonitis below its critical value was 26.6%and 27.3%,respectively.Conclusion:1.In this study,total lung V20 and MLD showed a certain degree of predictive value for the occurrence of RP in total lung cancer patients,which was consistent with the conclusions of many studies.2.Among the factors of hilar dose volume of peripheral lung cancer,only the volume of contralateral hilum showed a certain degree of significance in predicting the occurrence of symptomatic RP,and there was no significant correlation between the dose of contralateral hilum and symptomatic RP.3.The exposure dose of contralateral hilum of central lung cancer was generally correlated with the occurrence of symptomatic RP,and most of the dose volume factors of contralateral hilum showed different degree of predictive value for symptomatic RP.Hilum V30 and V40 had higher predictive value.4.When the volume of contralateral hilum of peripheral lung cancer was<49.9cm~3,the incidence of symptomatic radiation pneumonitis was 19.4%.The incidence of symptomatic radiation pneumonitis in contralateral hilar V30<25.5%and hilar V40<19.5%of central lung cancer was 26.6%and 27.3%,respectively.