Imaging proliferation in human leukemia-tumor bearing mice with (18)F-FLT: Comparison with (18)F-FDG PET.

Leukemia threatens human life due to its uncontrolled proliferative malignancy. 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) has been suggested as a new positron emission tomography (PET) tracer for imaging tumor proliferation. The aim of the study was to investigate the usefulness of (18)F-FLT PET for imaging human leukemia-tumor bearing mice, compared with fluorine-18-fluorodesoxyglucose ((18)F-FDG PET). In vitro the experiments of (18)F-FLT and (18)F-FDG uptake were performed in K562 cell lines at various time points and radioactive tracer uptake was measured in a gamma counter. (18)F-FLT and (18)F-FDG PET imaging were performed both in the same mouse when eight tumor-bearing mice models of human chronic myeloid leukemia were established successfully by injecting K562 cells. Regions of interest were drawn over the tumor, the crossed normal tissue was regarded as background and the ratio of tumor to non-tumor counts (T/NT) in tissues was calculated. A higher uptake of (18)F-FLT (15min, 5.73±0.05%; 30min, 5.90±0.06%; 60min, 6.16±0.19%; 120min, 6.32±0.08%) than that of (18)F-FDG (15min, 1.05±0.10%; 30min, 1.11±0.14%; 60min, 1.14±0.37%; 120 min, 1.36±0.25%) was observed in K562 cells in the tracer uptake experiment. Ratios of T/NT of (18)F-FLT PET (0.5h, 5.39±0.42; 1h, 4.88±0.43; 2h, 3.81±0.38) were higher than those of (18)F-FDG PET/CT (0.5h, 0.34±0.12; 1h, 0.21±0.06; 2h, 0.13±0.05) after injection. Both uptake and T/NT differences of (18)F-FLT versus (18)F-FDG were significant (P>0.05). In conclusion, (18)F-FLT and (18)F-FDG quantitative and semi-quantitative uptake measurements resulting from cell lines and PET imaging respectively suggested a promising potential of (18)F-FLT for metabolic imaging of human chronic myeloid leukemia.