Changes in ¹⁸F-FDG Uptake Within Minutes After Chemotherapy in a Rabbit VX2 Tumor Model

Abstract

The purpose of this study was to investigate whether 18 F-FDG PET/CT can be used for in vivo chemosensitivity testing and to determine the optimal time point for observation. Methods: Forty-two rabbits with 84 implanted VX2 squamous cell tumors were randomized into a control group (n 5 10) and a treatment group (n 5 32). 18 F-FDG PET/CT was performed the day before intravenous administration of cisplatin (4 mg/kg) and at 95-100 min (day 0), day 1, day 7, and day 14 afterward. In the control group, 18 F-FDG PET/CT images were acquired at the same time points but without cisplatin administration. Maximum standardized uptake value (SUV) and mean SUV were analyzed. On the basis of tumor volume, we categorized animal tumors into a sensitive group and an insensitive group. If tumor volume doubled by day 7, the tumor was considered insensitive. Results: On day 0, maximum SUV and mean SUV were significantly different between the sensitive group and the insensitive and control groups (P , 0.05 for both). In the sensitive group, the average change from the pretherapy values was 248.96% 6 12.27% for maximum SUV and 251.63% 6 10.45% for mean SUV. SUV did not significantly differ between the groups at any other points (days 1-14). On day 0, tumor volume was not significantly different between the control group and the sensitive or insensitive groups. After cisplatin administration, the size of the VX2 xenograft tumors increased slowly. Tumor necrosis fractions on days 7 and 14 were significantly greater in the sensitive group than in the insensitive or control group. Viable tumor cells on days 7 and 14 were less numerous in the sensitive group than in the insensitive or control group. A significant difference in inflammatory cells was seen between the sensitive and insensitive groups on days 7 and 14 (P , 0.05 for both). No significant differences in inflammatory cells or viable tumor cells were seen between the insensitive and control groups at any time points from before therapy to day 14 (P . 0.05 for all). A slight increase in viable tumor cells and inflammatory cells was seen in the sensitive group on day 14, compared with day 7. Conclusion: When 18 F-FDG was injected as early as 40 min after administration of chemotherapy, PET showed significantly decreased in vivo uptake of the tracer in chemoresponsive tumors. This finding suggests that 18 F-FDG PET may be able to discriminate sensitive from insensitive tumors if the imaging is performed immediately after a test dose of chemotherapy. The optimal observation time and methodology for various chemotherapy-tumor combinations will need to be studied to confirm whether this approach can be generalized.

Single-step syntheses of no-carrier-added functionalized [18F]fluoroarenes as labeling synthons from diaryliodonium salts

“…When an ethoxy-carbonyl group was present at meta -position in the precursor, the desired radiofluorinated ester [ 18 F] 28 was obtained in high yield (80%) (Table 3, entry 4; see ESI † for radio-HPLC chromatogram). This result appears consistent with a brief earlier report on the radiosynthesis of [ 18 F] 28 , 30 and in particular highlights the potential of functionalized diaryliodonium salt precursors for use in the radiosyntheses of other [ 18 F]fluoro-benzoic acid esters, including the otherwise difficult to access meta -substituted esters.…”

Small-Animal PET of Tumor Damage Induced by Photothermal Ablation with 64Cu-Bis-DOTA-Hypericin

“…PET using 18 F-FDG has long been recognized as a tool for therapy response assessment, revealing highly predictive values only 1-2 wk after the start of a therapy (11,12). The use of PET to measure therapeutic response has many advantages over biopsy-and surrogate tissuebased measurements, including the direct measurement of heterogeneous tumors and metastases repeatedly over time, with reduced statistical bias (13)(14)(15)(16). However, 18 F-FDG is not specific for cancer cells; inflammatory foci, sarcoidosis, and active tuberculosis are also shown as 18 F-FDG-positive lesions.…”

Cellular Imaging Using Equivalent Cross-Relaxation Rate Technique in Rabbit VX-2 Tumor Model

“…However, tumor response often involves the formation of necrosis without immediate size changes. Recently, diffusion-weighted MRI (DWI) and PET have been used to quantitatively evaluate tumor response and have been applied to the early response for chemotherapy 8–10. DWI evaluates the random motion of water molecules within the extracellular space, and can thus be used to indirectly evaluate tumor cellularity 11…”

“…Recently, diffusion-weighted MRI (DWI) and PET have been used to quantitatively evaluate tumor response and have been applied to the early response for chemotherapy. [8][9][10] DWI evaluates the random motion of water molecules within the extracellular space, and can thus be used to indirectly evaluate tumor cellularity. 11 In contrast, ECRI can be used to quantitatively evaluate changes in protein-water interactions and is able to directly provide information regarding the cell content when the offset frequency of the magnetization transfer pulse is less than 10 ppm.…”