Diagnostic Role of PET/CT Tracers in the Detection and Localization of Tumours Responsible for Ectopic Cushing's Syndrome

Abstract

Background/aim: Positron emission tomography/computed tomography (PET/CT) plays an important role in cancer localization in ectopic Cushing's syndrome (ECS). However, the choice of the optimal tracer for investigation of this disease is still unclear. We aimed to evaluate the diagnostic feasibility of [¹⁸F]fluoro-2-deoxyglucose ([¹⁸F]FDG), [¹⁸F]fluoro-L-dihydroxyphenylalanine ([¹⁸F] FDOPA), and [⁶⁸Ga]-DOTA-1-Nal3-octreotide ([⁶⁸Ga]-DOTANOC) in ECS.

Patients and methods: All PET/CT scans of patients admitted to our department for suspected ECS between 2010 and 2020 were retrospectively analysed.

Results: Collectively, 30 PET/CT examinations, 11 with [¹⁸F]FDOPA, 11 with [¹⁸F]FDG and 8 with [⁶⁸Ga]GaDOTANOC were conducted for 18 patients eligible for analysis. [¹⁸F]FDG detected the tumour in 3/6 of the cases, [¹⁸F]FDOPA in 3/4, and [⁶⁸Ga]GaDOTANOC in 3/3. [¹⁸F]FDOPA was the only tracer without false positive results.

Conclusion: [⁶⁸Ga]GaDOTANOC and [¹⁸F]FDOPA showed superior results compared to [¹⁸F]FDG, although the sensitivity of the tracers might be influenced by the aetiology of the tumour underlying the ECS.

Keywords: Ectopic Cushing’s syndrome; PET/CT; [18F]FDG; [18F]FDOPA; [68Ga]GaDOTANOC.