Untreated primary lung and breast cancers: Correlation between F-18 FDG kinetic rate constants and findings of in vitro studies

PURPOSE: To compare the kinetic modeling of 2-[fluorine-18]fluoro-2- deoxy-D-glucose (F-18 FDG) between untreated primary lung and untreated primary breast cancers by using position emission tomographic (PET) findings and to correlate the findings with findings of in vitro studies. MATERIALS AND METHODS: Nineteen patients (12 men, seven women; age range, 49-82 years) with untreated primary lung cancer and 17 women with untreated primary breast cancer (age range, 26-65 years) underwent 1-hour dynamic F-18 FDG PET. A three-compartment model was applied to F-18 FDG kinetics in tumors. The standard uptake value normalized for lean body mass (SUV(lean)) in tumors was measured 50-60 minutes after tracer injection. In vitro, thin-layer chromatography was performed to evaluate the intracellular phosphorylation of tritiated F-18 FDG in human lung cancer and breast cancer cell lines. RESULTS: At PEt, lung cancer had a significantly (P < .003) higher rate constant for F-18 FDG phosphorylation (k₃) and SUV(lean) than did breast cancer (0.161 ± 0.150 [standard deviation] vs 0.043 ± 0.018 and 8.25 ± 3.28 vs 3.17 ± 1.08, respectively). Breast cancer showed a significant correlation between k₃ and SUV(lean) (r = .607, P < .01), although no such correlation was observed in lung cancer. In vitro studies showed phosphorylation of F-18 FDG in breast cancer cells was less complete in hyperglycemia than it was in lung cancer cells. CONCLUSION: A much lower k₃ appears to be a rate-limiting factor for F-18 FDG accumulation in breast cancer, while the higher k₃ in lung cancer is probably not rate limiting for F-18 FDG accumulation.