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

Fluorine-18 fluorodeoxyglucose (F-18-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 (F-18-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 F-18-FDG and F-18-FLT. The male BALB/c mice were bilaterally inoculated with 1 x 10(5) and 1 x 10(6) C26 tumor cells per flank. Mice were intravenously treated with 10 mg/kg lipo-Dox at day 8 after F-18-FDG and F-18-FLT imaging. The biodistribution of F-18-FDG and F-18-FLT were followed by the microPET imaging at day 9. For the quantitative measurement of microPET imaging at day 9, F-18-FLT was superior to F-18-FDG for early detection of tumor response to Lipo-DOX at various tumor sizes (P < 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 F-18-FLT/microPET is a useful imaging modality for early detection of chemotherapy in the colorectal mouse model.