Synthesis and evaluation of [F-18]1-amino-3-fluorocyclobutane-1-carboxylicacid to image brain tumors

We have developed a new tumor-avid amino acid, 1-amino-3- fluorocyclobutane -1-carboxylic acid (FACBC), labeled with F-18 for nuclear medicine imaging. Methods: [F-18]FACBC was prepared with high specific activity (no carrier added [NCA]) and was evaluated for its potential in tumor localization. A c omparative study was performed for [F-18]FACBC and [F-18]2-fluorodeoxygluco se (FDG) in which the uptake of each agent in 9L gliosarcoma (implanted int racerebrally in Fisher 344 rats) was measured. In addition, the first human PET study of [F-18]FACBC was performed on a patient with residual glioblas toma multiforme. Quantitative brain images of the patient were obtained by using a Siemens 921 47-slice PET imaging system. Results: In the rat brain, the initial level of radioactivity accumulation after injection of [F-18]F ACBC was low (0.11 percentage injected dose per gram [%ID/g]) at 5 min and increased slightly to 0.26 %ID/g at 60 min. The tumor uptake exhibited a ma ximum at 60 min (1.72 %ID/g), resulting in a tumor-to-brain ratio increase of 5.58 at 5 min to 6.61 at 60 min. In the patient, the uptake of [F-18]FAC BC in the tumor exhibited a maximum concentration of 146 nCi/mL at 35 min a fter injection. The uptake of radioactivity in the normal brain tissue was low, 21 nCi/mL at 15 min after injection, and gradually increased to 29 nCi /mL at 60 min after injection. The ratio of tumor to normal tissue was 6 at 20 min after injection. The [F-18]FACBC PET scan showed intense uptake in the left frontal region of the brain. Conclusion: The amino acid FACBC can be radiofluorinated for clinical use. [F-18]FACBC is a potential PET tracer for tumor imaging.