Is [68Ga]Ga-DOTA-TATE PET/CT useful in the diagnosis of patients suspected of ectopic Cushing's syndrome?

Abstract

Introduction: Ectopic Cushing's syndrome (ECS) presents significant diagnostic and management challenges due to its varied clinical presentation and diagnostic uncertainties associated with conventional imaging methods. The aim of this study was to evaluate the effectiveness of [⁶⁸Ga]Ga-DOTA-TATE positron emission tomography/computed tomography (PET/CT) in diagnosing patients suspected of ECS with negative results from conventional imaging techniques.

Material and methods: In this retrospective single-institution study, data from January 2010 to August 2023 were analysed. Patients who underwent [⁶⁸Ga]Ga-DOTA-TATE PET/CT (Siemens Biograph 64) scans due to clinical and biochemical indicators of Cushing's syndrome were included, with prior conventional imaging yielding no abnormalities. The PET/CT scans were analysed qualitatively and quantitatively for any pathological foci. The study was conducted in accordance with ethical standards and approved by the Medical University of Warsaw's ethics committee.

Results: Of the 56 [68Ga]Ga-DOTA-TATE PET/CT scans performed on 44 patients, pathological accumulations were identified in 6 scans (11%) and 4 (9%) patients. Pathological findings were exclusively located within the thoracic cavity; lung lesions were identified in 3 patients, and 3 independent lesions within the anterior mediastinum and breast were observed in a single patient across 3 distinct scans. Histopathological analysis confirmed neuroendocrine tumours in all patients.

Conclusions: [⁶⁸Ga]Ga-DOTA-TATE PET/CT demonstrated limited potential for diagnostic value in patients suspected of ECS with negative outcomes according to conventional imaging. The percentage of patients who achieved positive results (10%) was not high, although other negative tests represented a significant percentage of the patients. This study highlights the need for further research and the development of novel radiotracers to improve ECS diagnosis.