Synthesis and Evaluation of 18F-Labeled Choline Analogs as Oncologic PET Tracers

Elevated levels of choline (trimethyl-2-hydroxyethylammonium) and choline kinase (CK) activity in neoplasms have motivated the development of positron-labeled choline analogs for noninva-sive detection of cancer using PET. The aim of this study was to further evaluate [18F]fluorocholine (fluoromethyl-dimethyl-2-hy-droxyethylammonium [FCH]) as an oncologic probe in comparison with several other closely related molecules. Methods: FCH, [18F]fluoromethyl-methylethyl-2-hydroxyethylammonium (FMEC), [18F]fluoroethyl-dimethyl-2-hydroxyethylammonium (FEC), and [18F]fluoropropyl-dimethyl-2-hydroxyethylammonium (FPC) were synthesized through [18F]fluoroalkylation reactions. In vitro phos-phorylation rates of the 18F-labeled choline analogs and [methyl-14C]choline (CH) were studied using yeast CK. Several choline radiotracers were also evaluated in cultured PC-3 human prostate cancer cells. Data on chemical stability, radiation dosimetry, an