Noninvasive Evaluation of Metabolic Tumor Volume in Lewis Lung Carcinoma Tumor-Bearing C57BL/6 Mice with Micro-PET and the Radiotracers (18)F-Alfatide and (18)F-FDG: A Comparative Analysis

PURPOSE: To explore the value of a new simple lyophilized kit for labeling PRGD(2) peptide ((18)F-ALF-NOTA-PRGD(2), denoted as (18)F-alfatide) in the determination of metabolic tumor volume (MTV) with micro-PET in lewis lung carcinoma (LLC) tumor-bearing C57BL/6 mice verified by pathologic examination and compared with those using (18)F-fluorodeoxyglucose (FDG) PET. METHODS: All LLC tumor-bearing C57BL/6 mice underwent two attenuation-corrected whole-body micro-PET scans with the radiotracers (18)F-alfatide and (18)F-FDG within two days. (18)F-alfatide metabolic tumor volume (V(RGD)) and (18)F-FDG metabolic tumor volume (V(FDG)) were manually delineated slice by slice on PET images. Pathologic tumor volume (V(Path)) was measured in vitro after the xenografts were removed. RESULTS: A total of 37 mice with NSCLC xenografts were enrolled and 33 of them underwent (18)F-alfatide PET, and 35 of them underwent (18)F-FDG PET and all underwent pathological examination. The mean ± standard deviation of V(Path), V(RGD,) and V(FDG) were 0.59±0.32 cm(3) (range,0.13~1.64 cm(3)), 0.61±0.37 cm(3) (range,0.15~1.86 cm(3)), and 1.24±0.53 cm(3) (range,0.17~2.20 cm(3)), respectively. V(Path) vs. V(RGD), V(Path) vs. V(FDG), and V(RGD) vs. V(FDG) comparisons were t = -0.145, P = 0.885, t = -6.239, P<0.001, and t = -5.661, P<0.001, respectively. No significant difference was found between V(Path) and V(RGD). V(FDG) was much larger than V(RGD) and V(Path). V(RGD) seemed more approximate to the pathologic gross tumor volume. Furthermore, V(Path) was more strongly correlated with V(RGD) (R = 0.964,P<0.001) than with V(FDG) (R = 0.584,P<0.001). CONCLUSIONS: (18)F-alfatide PET provided a better estimation of gross tumor volume than (18)F-FDG PET in LLC tumor-bearing C57BL/6 mice.