Dynamic observation of the radiosensitive effect of irisquinone on rabbit VX2 lung transplant tumors by using fluorine-18-deoxyglucose positron emission tomography/computed tomography

OBJECTIVE: We studied the radiosensitizing effect of irisquinone on a VX2 lung transplant tumor model during three-dimensional radiotherapy using fluorine-18-deoxyglucose ((18)F-FDG) PET/computed tomography (PET/CT). MATERIALS AND METHODS: Thirty VX2 tumor-bearing rabbits were randomized into three groups: the radiotherapy group, the irisquinone+radiotherapy group, and the control group, each comprising 10 rabbits. (18)F-FDG PET/CT images were obtained to monitor the tumor/muscle (T/M) ratio of F-FDG uptake and the retention index (RI) before treatment, when the radiation dose reached 6, 12, and 18 Gy, and 1 week after radiotherapy. Tumor volume changes were also assessed. The management of the control group followed the same procedure. RESULTS: At all treatment time points, the tumor volume was significantly smaller in the treatment groups than in the control group. The 1 and 2 h T/M ratios and RIs decreased gradually when the radiation dose reached 12 or 18 Gy in the treatment groups, whereas these values increased continuously in the control group. One week after treatment, the 1 and 2 h T/M ratios increased in the treatment groups, although these values remained lower than those in the control group. The RIs of the radiotherapy and irisquinone+radiotherapy groups were 0.329±0.133 and 0.137±0.036, respectively. Histological evaluation revealed that tumor F-FDG uptake was strongly related to tumor cell density. CONCLUSION: F-FDG PET/CT was sensitive and noninvasive and could be used to monitor the radiosensitizing effects of irisquinone and the therapeutic efficacy of radiotherapy.