Noninvasive assessment and quantification of tumor vascularization using [18F]FDG-PET/CT and CE-CT in a tumor model with modifiable angiogenesisan animal experimental prospective cohort study

BackgroundThis study investigated the noninvasive assessment of tumor vascularization with clinical F-18-fluorodeoxyglucose positron emission tomography/computed tomography and contrast-enhanced computed tomography ([18F]FDG-PET/CT and CE-CT) in experimental human xenograft tumors with modifiable vascularization and compared results to histology. Tumor xenografts with modifiable vascularization were established in 71 athymic nude rats by subcutaneous transplantation of human non-small-cell lung cancer (NSCLC) cells. Four different groups were transplanted with two different tumor cell lines (either A549 or H1299) alone or tumors co-transplanted with rat glomerular endothelial (RGE) cells, the latter to increase vascularization. Tumors were assessed noninvasively by [18F]FDG PET/CT and contrast-enhanced CT (CE-CT) using clinical scanners. This was followed by histological examinations evaluating tumor vasculature (CD-31 and intravascular fluorescent beads).ResultsIn both tumor lines (A549 and H1299), co-transplantation of RGE cells resulted in faster growth rates [maximal tumor diameter of 20mm after 22 (1.2) as compared to 45 (+/- 1.8) days, p<0.001], higher microvessel density (MVD) determined histologically after CD-31 staining [171.4 (+/- 18.9) as compared to 110.8 (+/- 11) vessels per mm(2), p=0.002], and higher perfusion as indicated by the number of beads [1.3 (+/- 0.1) as compared to 1.1 (+/- 0.04) beads per field of view, p=0.001]. In [18F]FDG-PET/CT, co-transplanted tumors revealed significantly higher standardized uptake values [SUVmax, 2.8 (+/- 0.2) as compared to 1.1 (+/- 0.1), p<0.001] and larger metabolic active volumes [2.4 (+/- 0.2) as compared to 0.4 (+/- 0.2) cm(3), p<0.001] than non-co-transplanted tumors. There were significant correlations for vascularization parameters derived from histology and [18F]FDG PET/CT [beads and SUVmax, r=0.353, p=0.005; CD-31 and SUVmax, r=0.294, p=0.036] as well as between CE-CT and [18F]FDG PET/CT [contrast enhancement and SUVmax, r=0.63, p<0.001; vital CT tumor volume and metabolic PET tumor volume, r=0.919, p<0.001].Conclusions In this study, a human xenograft tumor model with modifiable vascularization implementable for imaging, pharmacological, and radiation therapy studies was successfully established. Both [18F]FDG-PET/CT and CE-CT are capable to detect parameters closely connected to the degree of tumor vascularization, thus they can help to evaluate vascularization in tumors noninvasively. [18F]FDG-PET may be considered for characterization of tumors beyond pure glucose metabolism and have much greater contribution to diagnostics in oncology.