PET has been used to monitor changes in
tumor metabolism in
breast cancer following hormonal
therapy. This study was undertaken to determine whether PET imaging could evaluate early metabolic changes in prostate
tumor following
androgen ablation
therapy. Studies were performed comparing two positron-emitting tracers,
18F-FDG and 11C-acetate, in Sprague-Dawley male rats to monitor metabolic changes in normal prostate tissue. Additional studies were performed in nude mice bearing the CWR22
androgen-dependent human prostate
tumor to evaluate metabolic changes in prostate
tumor. In rats, for the
androgen ablation pretreatment, 1 mg
diethylstilbestrol (DES) was injected subcutaneously 3 and 24 hours before tracer injection. For
androgen pretreatment, 500 microg
dihydrotestosterone (DHT) was injected intraperitoneally 2 and 6 hours before tracer injection. The rats were divided into three groups, Group A (no-DES, no-DHT, n = 18), Group B (DES, no-DHT, n = 18) and Group C (DES, DHT, n = 18). In each group, 10 animals received
18F-FDG, whereas the remaining eight animals were administered 11C-acetate. Rats were sacrificed at 120 min post-injection of
18F-FDG or 30 min post-injection of 11C-acetate. Pretreatment of the mouse model using DHT (200 microg of DHT in 0.1 mL of
sunflower seed oil) or DES (200 microg of DES in 0.1 mL of
sunflower seed oil) was conducted every 2 days for one week. Mice were imaged with both tracers in the microPET scanner (Concorde Microsystems Inc.). DES treatment caused a decrease in
acetate and
glucose metabolism in the rat prostate. Co-treatment with DHT maintained the
glucose metabolism levels at baseline values. In the
tumor bearing mice, similar effects were seen in
18F-FDG study, while there was no significant difference in 11C-acetate uptake. These results indicate that changes in serum
testosterone levels influence
18F-FDG uptake in the prostate gland, which is closely tied to
glucose metabolism, within 24 hours of treatment and in the prostate
tumor within 1 week. These early metabolic changes could enable monitoring metabolic changes in prostate
tumor following treatment by imaging using
18F-FDG PET. Further studies are needed to clarify the reason for the insensitivity of 11C-acetate for measuring metabolic change in prostate
tumor.