Evaluation of the early reaction of three-dimensional conformal radiotherapy in rabbit lung VX2 transplant tumor by ~(18)F-FDG PET/CT

Objective To study the characteristics of 18F-FDG PET/CT imaging in rabbit lung VX2 transplant tumor during three-dimensional conformal radiotherapy,and to explore the value of 18F-FDG PET/CT to assess the efficacy of tumor radiotherapy.Methods Sixteen tumor-bearing rabbits were evenly and randomly divided into 2 groups(8 rabbits in each group): radiotherapy group and control group.18F-FDG PET/CT imaging was performed when radiation cumulative dose achieved 0,6,12 and 18 Gy.The delayed tumor tissue SUVmax(maximum standardized uptake value),the contralateral lung tissue SUVmax,the ratio of the two(T/L) and the change of tumor volume were monitored by 18F-FDG PET/CT.The rabbits in each group were sacrificed after 18F-FDG PET/CT imaging,HE staining observing the change of pathology.Results When radiation cumulative dose achieved 0,6,12 and 18 Gy,T/L of tumor-bearing rabbits in radiotherapy group were(8.447±1.488),(9.344±1.342),(7.143±1.307),(6.221±1.066).The differences at each time were statistically significant(t=3.679,5.010,5.984,all P0.05).T/L of tumor-bearing rabbits in control group gradually increased:(8.428±1.705),(9.610±1.282),(10.402±1.283),(11.586±1.627).The differences at each time were statistically significant(t=3.360,3.225,2.611,all P0.05).Tumor volume grew in two groups,When radiation cumulative dose achieved 6,12 and 18 Gy,tumor volumes of each group were statistically significant(2.742,5.225,6.824,all P0.05),however tumor volume growth in radiotherapy group was slower than that in control group.HE staining showed large areas of necrosis within the tumor tissue of the radiotherapy group,and the activity of tumor cells was significantly less in the control group.Conclusion 18F-FDG PET/CT imaging in rabbit lung VX2 transplant tumor during three-dimensional conformal radiotherapy showed T/L significantly reduced in a short time,which can evaluate the early reaction of radiotherapy before morphology changes.