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 SUV_max 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 SUV_max 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 SUV_max 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 SUV_max decrease rate was (42.33 ± 33.80)%, the mean T/NT decrease rate was (83.50 ± 7.69)%. The SUV_max 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 SUV_max 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. (authors)