Gallium-68 PET: a new frontier in receptor cancer imaging

Neuroendocrine tumours (NET) are rare tumours that occur most commonly in the GI tract. Various labelled somatostatin analogues are used to image NET expressing somatostatin receptors (SSTR). In traditional nuclear medicine, most peptides used in imaging NET have been labelled with indium-111, the commonest being indium-111-octreotide (111In-octreotide). Unfortunately, the unfavourable physical qualities of In-111 make it unsuitable for detecting small tumour deposits. The recent introduction of gallium-68-1,4, 7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (gallium-68-DOTA) compounds for positron emission tomography (PET) imaging has significantly improved the quality of imaging NET through improved resolution of PET and higher affinity of the new generation of peptides to SSTR. In the present paper, we discuss the clinical and research applications of PET radio-tracers for evaluating NET, in particular gallium-68-DOTA compounds. The recent introduction of PET imaging with gallium-68 has major bearings in current and future clinical practice. Its labelling with DOTA compounds has cleared the way for somatostatin receptor imaging with a viable PET agent, with all its inherent imaging advantages compared to single photon imaging. The pre-clinical and clinical applications of this technique has been successful in a variety of tumours, particularly NET and its labelling with other ligands and molecules will improve the management of other tumours and the assessment of infection.