Characterization of Osteolytic, Osteoblastic, and Mixed Lesions in a Prostate Cancer Mouse Model Using 18F-FDG and 18F-Fluoride PET/CT

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Abstract
The combination of small-animal PET/CT scans and conventional imaging methods may enhance the evaluation of in vivo biologic interactions of murine models in the study of prostate cancer metastasis to bone. Methods: Small-animal PET/CT scans using 18F-fluoride ion and 18F-FDG coregistered with high-resolution small-animal CT scans were used to longitudinally assess the formation of osteoblastic, osteolytic, and mixed lesions formed by human prostate cancer cell lines in a severe combined immunodeficient (SCID) mouse tibial injection model. These scans were correlated with plain radiographs, histomorphometry, and soft-tissue measurements. Results: Small-animal PET/CT scans were able to detect biologic activity of cells that induced an osteoblastic lesion 2 wk earlier than on plain radiographs. Furthermore, both the size and the activity of the lesions detected on PET/CT images significantly increased at each successive time point (P < 0.05). 18F-FDG lesions strongly correlated with soft-tissue measurements, whereas 18F-fluoride ion activity correlated with bone volume measured on histomorphometric analysis (P < 0.005). Osteolytic lesions were successfully quantified using small-animal CT, whereas lesion sizes measured on 18F-FDG PET scans also strongly correlated with soft-tissue tumor burden (P < 0.05). In contrast, for mixed lesions, 18F-fluoride ion and 18F-FDG PET/CT scans detected only minimal activity. Conclusion: 18F-FDG and 18F-fluoride ion PET/CT scans can be useful tools in characterizing pure osteolytic and osteoblastic lesions induced by human prostate cancer cell lines. The value of this technology needs further evaluation to determine whether these studies can be used effectively to detect more subtle responses to different treatment regimens in animal models.