INSULIN-INDUCED HYPOGLYCEMIA DECREASES UPTAKE OF 2-[F-18] FLUORO-2-DEOXY-D-GLUCOSE TO EXPERIMENTAL MAMMARY-CARCINOMA

PURPOSE: To determine, in an animal study, whether insulin-induced hyp oglycemia enhances tumor uptake of 2-[fluorine-18]fluoro-2-deoxy-D-glu cose (FDG) in vivo. MATERIALS AND METHODS: Rat mammary tumors were est ablished subcutaneously in Lewis rats. When the tumor was 1-2 cm in di ameter, rats were fasted overnight and divided into two groups: contro l rats (n = 5) that received saline and hypoglycemic rats (n = 5) that received insulin. After 30 minutes, FDG (200 mu Ci [7.4 MBq]) was giv en intravenously. One hour after FDG injection (ie, at sacrifice), pla sma glucose and insulin levels were measured and F-18 activity in tumo r and normal tissues was determined. RESULTS: Mean glucose level was 3 2.8 mg/dL (1.8 mmol/L) and mean insulin level was 2,831.1 mu U/mL (20, 315 pmol/L) in the hypoglycemic animals. As compared with the control value, mean FDG uptake in tumor (percentage of injected dose [per gram of tissue] per kilogram of animal weight) significantly decreased wit h hypoglycemia (0.117 vs 0.331, P = .0001). Mean FDG uptake in the hea rt and muscle was 9.75 and 5.18 times higher, respectively, in the hyp oglycemic rats (P = .0001). Thus, the tumor/muscle uptake ratio was si gnificantly reduced with hypoglycemia (2.15 vs 31.62, P = .0002). CONC LUSION: Tumor targeting with FDG is impaired, not enhanced, by insulin -induced hypoglycemia.