Application Of Combined Body Position Fixation In Radiation Therapy Of Lung Cancer

Objectives A comparative analysis of combined body position and thermoplastic film fixed set-up error of radiation therapy for lung cancer,to explore the CTV to PTV external expansion boundary and the effect of the dose of normal lung tissue under different fixed modes.Methods From October 2016 to March 2018,the patients who received lung cancer radiology at the Tangshan people’s hospital were enrolled as subjects,which retrospectively divided into two groups,including 50 patients with lung cancer radiotherapy with combined body position fixation,and 40 patients with lung cancer with thermoplastic film fixation.The two groups of patients drew the target areas in accordance with the unified standard,and the set-up error of left and right,up and down,front and rear（X,Y,Z axis）were recorded respectively after 1 times/week cone CT（CBCT）matched with the planned CT image.The general clinical data were analyzed by K-S test.T-test of two independent samples was used to analyze the setup errors between the combined body position group and the thermoplastic membrane group,and also the central and peripheral lung cancer patients,the left and right lung cancer patients,as well as the upper lobe and the middle and lower lobe cancer patients.According to the M_PTV=2.5 Sigma+0.7 Delta,we calculated CTV to PTV external expansion boundary in the combined body position group.The combined body position group was defined as group A and the virtual experimental group was set as group B.The data of group A and group B were analyzed by t-test of paired samples.And the V₅、V₂₀ and V₃₀ of two groups of patients were calculated and analyzed by TPS system.Results The set-up error of the combined body position group and thermoplastic film group were respectively in the X axis（1+0.58）mm and（3.28+0.43）mm（P=0.026）,in the Y axis（1.42+0.28）mm and（4.03+0.41）mm（P=0.001）,in the Z axis（1.06+0.44）mm and（3.18+0.34）mm（P=0.022）.The set-up errors of the two groups were statistically significant on X,Y and Z axis（t=-20.74,-35.596,-25.015,P<0.05）.There was no significant difference in set-up errors between the central and peripheral lung cancer patients（t=-0.649,-0.109,-0.164,P=0.228,0.922,0.677）,and also left and right lung cancer patients（t=-0.130,0.125,-0.384,P=0.296,0.265,0.141）,as well as upper lobe and lower lobe lung cancer（t=0.210,0.458,1.153,P=0.834,0.649,0.255）.Through the M_PTV=2.5 Sigma+0.7 Delta,CTV to PTV external expansion boundary in the combined body position fixation group was2.906mm,3.746mm and 2.958mm on X,Y and Z axis respectively.The combined body group was defined as group A（PTV extension boundary was 5mm）,and the virtual experimental group was set（under the premise of ensuring that 90%patients received at least 95%of the prescribed dose of CTV,the PTV extension boundary x and z of group A patients were set as 3 mm;Y axis is set as 4 mm）and is defined as group B.The comparison between group A and B shows that the mean values of V₅,V₂₀ and V₃₀ in group B were reduced by 1.5%,3.1%and 4.8%respectively compared with those in group A（t=12.182,10.480,10.325,P=0.000,0.000,0.000）.Conclusions 1 The combined position fixation technique has high anastomosis,good repeatability and comfort in the position fixation of thoracic cancer radiotherapy,provideing a new and effective position fixation method for the radiotherapy of thoracic tumor.2 In the treatment of lung cancer patients with combined position fixation technology,the setup errors of X,Y and Z axes are reduced,and the boundary between CTV and PTV can be further narrowed.3 There is no significant difference in the application of combined postural fixation technique in central and peripheral lung cancer,and also left and right lung cancer,as well as upper and lower lobes lung cancer,all that have the same effect.4 In group A,the X,Y and Z axes were extended 5 mm.In group B,X and Z axes were extended 3 mm and Y axes 4 mm.The results showed that V₅,V₂₀ and V₃₀ were all reduced,which provided the basis for reducing the severity of radiation-induced lung injury,especially radiation pneumonia.Figure 8;Table 7;Reference 148...