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Endocrine Abstracts (2015) 37 OC1.4 | DOI: 10.1530/endoabs.37.OC1.4

ECE2015 Oral Communications Adrenal 1 (5 abstracts)

11C-metomidate PET-CT in primary aldosteronism: five possible indications for a non-invasive alternative to adrenal vein sampling

Andrew S Powlson 1 , Olympia Koulouri 1 , Elena Azizan 2 , Carmela Maniero 2 , Kevin Taylor 3 , Franklin Aigbirhio 4 , Brendan Koo 5 , Heok K Cheow 6 , John Buscombe 6 , Mark Gurnell 1 & Morris J Brown 2


1Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, UK; 2Clinical Pharmacology Unit, University of Cambridge, Cambridge, UK; 3Department of Clinical Biochemistry, University of Cambridge, Cambridge, UK; 4Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK; 5Department of Radiology, Addenbrooke’s Hospital, Cambridge, UK; 6Department of Nuclear Medicine, Addenbrooke’s Hospital, Cambridge, UK.

Background: Adrenal vein sampling (AVS) remains the gold-standard for distinguishing unilateral and bilateral disease in primary aldosteronism (PA). However, it is invasive, technically demanding, and may yield inconclusive or equivocal results. 11C-Metomidate PET-CT (11C-MTO-PET-CT) is a non-invasive alternative to AVS for localising unilateral aldosterone-producing adenomas (APAs).

Methods/patients: We report a retrospective analysis of 61 sequential patients with PA referred for 11C-MTO-PET-CT in the three years since our original study (Burton et al., JCEM 2012). All had a definite/possible adenoma on previous CT/MRI or AVS suggesting lateralisation.

Results: 11C-MTO-PET-CT was unequivocally positive leading to a recommendation for surgery in 26/61 patients (42.6%). In all 12 cases operated locally to date (unilateral adrenalectomy), adrenocortical histology and CYP11B2 immunopositivity was confirmed, with biochemical cure of PA (normalisation of the aldosterone-to-renin ratio); six patients await adrenalectomy. In a further eight ‘tertiary’ referrals from elsewhere, lateralisation by 11C-MTO-PET-CT led to a recommendation for adrenalectomy, but clinical outcome data is awaited. Finally, where multiple nodules co-existed, 11C-MTO-PET-CT accurately identified the causative tumour (confirmed by cell-culture, gene-expression and genotyping).

Discussion: The 26 patients in whom unilateral disease was confirmed had one of five indications for 11C-MTO-PET-CT: i) AVS technically unsuccessful (failure to cannulate one of the adrenal veins); ii) technically adequate AVS, but without clear lateralisation; iii) AVS not possible (unable to safely withdraw spironolactone or epleronone); iv) no clear-cut abnormality on cross-sectional imaging; and v) patient choice not to undergo AVS. 11C-MTO-PET-CT was also valuable in providing strong evidence against lateralisation, especially in patients with a definite unilateral adenoma on CT/MRI, but no resolution by AVS. In conclusion, analysis of 11C-MTO-PET-CT in 61 sequential patients supports its use as an adjunct/non-invasive alternative to AVS. In addition, we speculate that 11C-MTO-PET-CT may facilitate non-surgical targeted nodule-specific ablation or selective surgical adenomectomy when multiple nodules are present.

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