ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 P445 | DOI: 10.1530/endoabs.63.P445

11C-Metomidate PET/CT Identifies Unilateral Primary Aldosteronism in a Multi-ethnic Cohort

Troy Puar1, Colin Tan1,2, Aaron Tong2,3, Meifen Zhang1, Chin Meng Khoo4, Alvin Tan5, Htoo Htoo6, Anthonin Reilhac7, Ashley Weekes7, Ed Robins7 & Roger Foo4,8,9

1Changi General Hospital, Singapore, Singapore; 2Singapore General Hospital, Singapore, Singapore; 3Sengkang Hospital, Singapore, Singapore; 4National University Health System, Singapore, Singapore; 5Tan Tock Seng Hospital, Singapore, Singapore; 6Khoo Teck Puat Hospital, Singapore, Singapore; 7Clinical Imaging Research Centre, Singapore, Singapore; 8Genomic Institute of Singapore, Singapore, Singapore; 9Cardiovascular Research Institute, Singapore, Singapore.

Introduction: Patients with unilateral primary aldosteronism (PA) can be cured with adrenalectomy, and adrenal vein sampling (AVS) remains the gold-standard test. However, AVS is invasive, technically-challenging and criteria for determining lateralization differ between centres. 11C-Metomidate PET/CT (MTO) imaging offers a promising non-invasive alternative for identifying unilateral PA.

Methods: All patients with confirmed primary aldosteronism who were keen for a surgical cure underwent both AVS and MTO. AVS was done under continuous ACTH-stimulation and successful cannulation was demonstrated if adrenal vein cortisol was greater than peripheral vein cortisol by >5. All test results including CT, AVS and MTO were reviewed by a multi-disciplinary panel to determine unilateral PA. The accuracies of MTO and AVS to identify unilateral PA were compared to the final conclusion of the multi-disciplinary panel.

Results: 12 patients, mean age 48.9±9.3 yr, 6 females (50.0%) were enrolled in the study, with 8 patients Chinese (66.7%), 3 Malay (25.0%), and 1 of other ethnicity (8.3%). 9 patients were deemed to have unilateral PA by the panel, with AVS identifying 8 (sensitivity 88.9%) and MTO identifying 7 (sensitivity 77.8%). All 12 patients had successful AVS (bilateral cannulation), with 8 patients having lateralization ratio >4, consistent with unilateral PA. MTO identified 7 patients with unilateral PA, and the mean SUVmax of the tumor was 37.1±8.7, while the mean SUVmax of the contralateral normal gland was 22.7±5.8. In these patients, the mean SUVmax ratio of tumor: contralateral adrenal was 1.69±0.39. Three patients had bilateral PA on both AVS and MTO, and the mean SUVmax of the adrenals was 21.8±5.5. Two patients had lateralization on AVS, but on MTO, the tumor SUVmax (26.3±18.3) was lower than the normal contralateral gland (38.4±30.6). One patient with lateralization on MTO (Lateralization SUVmax ratio of 1.48) did not lateralize with AVS.

Conclusion: 11C-Metomidate PET/CT has potential to accurately identify patients with unilateral PA, and this may obviate the need for invasive adrenal vein sampling. While most patients have congruent findings on both AVS and MTO, these tests may identify different subtypes of unilateral PA. Further genotyping of these tumors will be important to understand further the underlying pathophysiology and the utility of these localization tests.