PET imaging in endocrine tumours

The role of PET in the assessment of endocrine tumours has been, until recently, restricted to the use of (18)F-fluoro-deoxy-D-glucose ((18)F-FDG). Being a marker of metabolically active lesions that show high grading and low differentiation, FDG is not ideal for this purpose since the majority of endocrine tumours are slow growing and highly differentiated. It is however useful when dedifferentiation takes place and provides excellent prognostic information. A number of hormone precursors and amino acids are labelled with (11)C and used successfully in the management of parathyroid, adrenal and pituitary tumours. However, the short half-life of (11)C radiopharmaceuticals restricts their use to centres with access to an on-site cyclotron, while the high cost of production may limit their use to research purposes. A promising new positron-emission tomography (PET) tracer is Gallium-68 obtained by elution from a long shelf-life generator that makes it economic and cyclotron-independent. Its short half-life and flexible labelling ability to a wide range of peptides and antibodies makes it ideal for PET imaging. In addition to imaging GEP-NETs and phaeochromocytoma, it has the potential to be used in a wider range of endocrine tumours.