Comparative Study Of Radiotherapy Dosimetry Between Helical Tomotherapy(TOMO) And Static Intensity-Modulated Radiotherapy(IMRT) In The Treatment Of Locally Advanced Non-Small Cell Lung Cancer

Objective:A comparative study of radiotherapy physical dosimetry between helical tomotherapy(TOMO)and static intensity-modulated radiotherapy(IMRT)in the treatment of locally advanced non-small cell lung cancer,to compare the advantages and disadvantages of the physical parameters of the target area irradiated by the two radiotherapy techniques,as well as the effects of the two radiotherapy techniques on the irradiation dose and volume of sensitive organs,so as to explore the applicable scope of TOMO and IMRT in the treatment of locally advanced non-small cell lung cancer with different primary tumor types,different sites and different PTV target volumes.Methods: Thirty patients with locally advanced non-small cell lung cancer who were treated in our hospital from November 2016 to December 2021 were collected,and their previous CT simulated localization images were used to design IMRT and TOMO radiotherapy plans respectively.The same CT simulation images,the same target volume delineation and dose were used for each patient(6MV-X ray was used,dose: PGTV-T=66Gy/2Gy/30 F,PGTVnd=60Gy/2Gy/30 F,PTV=54Gy/1.8 Gy/30F),and the same ORR delineation and ORR limits(whole lung V5 < 50%;whole lung V20 < 30%;heart V30 < 40%;heart V40 < 30%;esophagus V50 < 50%;spinal cord Dmax <45Gy).Design TOMO plan and IMRT plan on Tomotherapy plan system and Pinnacle plan system respectively.Among them,the TOMO plan entered the TOMO group,and the IMRT plan entered the IMRT group.The radiation dosimetry parameters of two sets of planned PGTV-T and PTV were collected: conformity index(CI),heterogeneity index(HI);whole lung V5,V20;heart V30,V40;spinal cord Dmax;Esophageal V50.Statistical analysis and comparison were performed according to the type of primary tumor(peripheral or central),tumor location(left or right lung),and PTV size.Results: 1.Compared with IMRT technology,TOMO technology showed higher CI in PTV CI,indicating that the TOMO group had better conformity,and the difference was statistically significant(P<0.05);The PTV HI in the TOMO group was higher than that in the IMRT group.The higher the HI,the worse the homogeneity of the target area,that is,the PTV homogeneity in the TOMO group was worse,and the difference was statistically significant(P<0.05);The PGTV-T HI of the TOMO group was lower than that of the IMRT group,indicating that the PGTV-T homogeneity of TOMO was better,and the difference was statistically significant(P<0.05);PGTV-T CI in TOMO group was better than PGTV-T CI in IMRT group in PGTV-T CI,but the difference was not statistically significant(P>0.05).2.The TOMO group was superior to the IMRT group in the parameters of whole lung V20 and cardiac V30,and the differences were statistically significant(P<0.05);The exposure volume of whole lung V5 in the IMRT group was better than that in the TOMO group,and the difference was statistically significant(P<0.05);In the data of heart V40,esophagus V50,spinal cord Dmax and other data,there was no statistical difference between the two planning parameters(P>0.05).3.According to the type of primary tumor,the primary tumor types of the collected patients were divided into central locally advanced NSCLC and peripheral locally advanced NSCLC.In the TOMO plan of central locally advanced NSCLC,the mean values of whole lung V20 and cardiac V30 decreased,with statistical difference(P<0.05);There was no significant difference in the data of organs at risk such as whole lung V5,heart V40,esophagus V50,and spinal cord Dmax(P>0.05);In peripheral locally advanced NSCLC,the values of whole lung V5 and cardiac V40 of IMRT radiotherapy plan were better than TOMO plan,and the difference was statistically significant(P<0.05);There was no significant difference in the dose parameters of V20 in the whole lung,V30 in the heart,V40 in the esophagus,and Dmax in the spinal cord between the two radiotherapy plans(P>0.05).4.According to the location of the primary tumor,the collected locally advanced NSCLC was divided into left lung locally advanced NSCLC and right lung locally advanced NSCLC.In locally advanced NSCLC tumors in the left lung,TOMO plan was superior to IMRT plan in irradiated volume of whole lung V20 and heart V30,and the difference was statistically significant(P<0.05);But there was no statistical difference in whole lung V5,heart V40,esophagus V50 and spinal cord Dmax(P>0.05);In the right lung locally advanced NSCLC,compared with the TOMO plan and the IMRT plan,the lung V5,lung V20,heart V30,heart V40,esophagus V50,spinal cord Dmax and other organ-at-risk parameters were not significantly different between the two plans(P >0.05).5.We calculated the size of PTV in the target volume of the collected 30 cases,taking the median PTV volume of 337.6cm~3,divided into large target volume locally advanced NSCLC(≥337.6cm~3)and small target volume locally advanced NSCLC(<337.6cm~3)).In patients with locally advanced NSCLC with large target area,the whole lung V20 performance of TOMO plan was better than that of IMRT plan,and the difference was statistically significant(P<0.05);There was no significant difference between the two plans in the parameters of whole lung V5,heart V30,heart V40,esophagus V50,and spinal cord Dmax(P>0.05);For locally advanced NSCLC with small target area,TOMO plan and IMRT plan are compared in terms of organ-at-risk parameters such as whole lung V5,whole lung V20,heart V30,heart V40,esophagus V50,and spinal cord Dmax.There was no statistically significant difference in the values(P>0.05).Conclusion: 1.TOMO plan has better radiation conformity but poor uniformity of PTV target volume in the treatment of locally advanced lung cancer;The homogeneity of the PGTV-T target volume of the TOMO plan was better than that of the IMRT plan,and there was no statistical difference in conformity between the two.2.The TOMO plan has better restrictions on the parameters of whole lung V20 and cardiac V30 than the IMRT plan;There was no significant difference in the limitation of organ-at-risk parameters such as heart V40,esophagus V50,and spinal cord Dmax.Whether the disadvantage of TOMO planning in whole lung V5 will lead to an increased incidence of radiation pneumonitis should be further studied.3.From the point of view of the limitation of dose to organs at risk,TOMO plan may be more suitable for locally advanced non-small cell lung cancer with central type,left lung and larger target area;For peripheral,right lung,and locally advanced non-small cell lung cancer with a smaller target area,both can be selected.Choosing the IMRT plan can reduce the economic burden of patients and save medical insurance expenses.