Early Detection of Tumor Response by FLT/MicroPET Imaging in a C26 Murine Colon Carcinoma Solid Tumor Animal Model

Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) imaging demonstrated the change of glucose consumption of tumor cells, but problems with specificity and difficulties in early detection of tumor response to chemotherapy have led to the development of new PET tracers. Fluorine-18-fluorothymidine (18F-FLT) images cellular proliferation by entering the salvage pathway of DNA synthesis. In this study, we evaluate the early response of colon carcinoma to the chemotherapeutic drug, lipo-Dox, in C26 murine colorectal carcinoma-bearing mice by 18F-FDG and 18F-FLT. The male BALB/c mice were bilaterally inoculated with 1×105 and 1×106 C26 tumor cells per flank. Mice were intravenously treated with 10 mg/kg lipo-Dox at day 8 after 18F-FDG and 18F-FLT imaging. The biodistribution of 18F-FDG and 18F-FLT were followed by the microPET imaging at day 9. For the quantitative measurement of microPET imaging at day 9, 18F-FLT was superior to 18F-FDG for early detection of tumor response to Lipo-DOX at various tumor sizes (<0.05). The data of biodistribution showed similar results with those from the quantification of SUV (standard uptake value) by microPET imaging. The study indicates that 18F-FLT/microPET is a useful imaging modality for early detection of chemotherapy in the colorectal mouse model.