18F-FDG PET/CT monitoring for early tumor response to cisplatin in VX2 tumor-bearing rabbits

Objective To evaluate the value of 18F-FDG PET/CT in early in vivo monitoring of tumor response to cisplatin, and analyze the relationship between 18F-FDG uptake in tumor and the corresponding pathological changes. Methods Thirty VX2 rabbits were divided into 5 groups by random number table with 6 in each group, including 4 treatment groups and 1 control group. 18F-FDG PET/CT were performed before and after (6, 12, 24 and 36 h post-injection respectively) intravenous administration of cisplatin (7 mg/kg) in the treatment groups, respectively. The control group was injected with physiological saline followed by 18F-FDG PET/CT. The ROI was drawn and the SUVmax and T/NT ratio were calculated. The tumor necrosis rate and apoptosis index were observed by histopathologic examination. Paired t test, Games-Howell test and arcuation correlation analysis were used to analyze the data. Results Significant differences were found in SUVmax and T/NT of the control group before and after injection of physiological saline (6.58±1.67 vs 9.77±2.45, 52.93±3.90 vs 29.34±3.31; t=-5.480, 17.593, both P<0.05). 18F-FDG uptake decreased after 6 h post-injection of cisplatin, with the mean SUVmax decrease rate of (11.83±8.89)% and the mean T/NT decrease rate of (59.00±8.22)%. In the 24 h treatment group, 18F-FDG uptake decreased most, and the mean SUVmax decrease rate was (42.33±33.80)%, the mean T/NT decrease rate was (83.50±7.69)%. The SUVmax and T/NT of those 2 groups were significantly different from those of the control group, and no difference was found between the 2 treatment groups(all P<0.05). The changes of SUVmax and T/NT were positively correlated with apoptosis index and tumor necrosis rate (r=0.750, 0.794, 0.804, 0.874, all P<0.05). Conclusion 18F-FDG PET/CT is a sensitive method for monitoring early response to tumor chemotherapy in VX2 tumor-bearing rabbits at 24 h after treatment. Key words: Carcinoma, squamous cell; Neoplasm transplantation; Chemotherapy; Cisplatin; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose; Rabbits