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Cardiovascular Endocrinology

ORF23-04 - Prospective Clinical Trial Comparing [ 11 C]-Metomidate PET/CT Versus Adrenal Vein Sampling to Identify Unilateral Primary Aldosteronism

Sunday, June 14, 2026
9:45 AM - 10:00 AM CT
Location: Room W185ABC



Introduction: Primary Aldosteronism (PA) is a common cause of secondary hypertension. Adrenal vein sampling (AVS) remains the standard for subtyping PA; however, its invasive and technically challenging nature restricts availability, narrowing patients’ opportunities for potentially curable surgery. We compared the accuracy of non-invasive 11C-Metomidate (MTO) PET/CT vs. AVS in diagnosis of unilateral PA.

Study

Design: We conducted a prospective, within-patient, multicenter clinical trial enrolling patients with confirmed PA. All patients underwent both AVS and MTO PET/CT. Subtyping test results were reviewed in a multidisciplinary meeting to recommend medical or surgical management. Unilateral adrenalectomy was offered to patients with clear lateralization on either/both AVS (lateralization index ≥4), MTO PET/CT (SUVmax over an adrenal nodule >1.25 times of the SUVmax of the contralateral gland). The study was powered to demonstrate non-inferiority of MTO PET/CT vs AVS in identifying unilateral PA as confirmed by complete biochemical success using PA Surgical Outcome (PASO) consensus (margin −17%; 90% power; α=0.01). Secondary outcomes included comparison of MTO PET/CT vs. AVS in predicting classical unilateral PA as defined by HISTALDO consensus using CYP11B2-immunohistochemical (IHC) staining, distribution of somatic mutations in resected adrenals using Sanger and whole exome sequencing, and use of hybrid hormones (18-oxocortisol and 18-hydroxycortisol) for predicting KCNJ5-mutant unilateral PA. (ClinicalTrials.gov: NCT06100367).

Results: A total of 106 patients with PA underwent both subtyping tests (mean age 48.4 ± 10.1 years, 71.0% males), of which 101 patients completed follow-up at >6 months post-treatment. Unilateral PA was identified in 30 patients by both tests, 17 by PET/CT only, and 18 by AVS only. Five patients with bilateral PA elected for surgery, and 1 patient with unilateral PA was lost to follow-up. Eventually, surgery was performed in 69 patients; among these, 64 (92.8%) achieved complete biochemical success, 4 (5.8%) had absent biochemical success, and 1 awaited final evaluation. CYP11B2-IHC staining was performed in 52 resected adrenals, and classical unilateral PA was identified in 46 (88.5%). MTO PET/CT and AVS identified classical unilateral PA in 32 (69.6%) and 31 (67.4%) cases, respectively. Somatic mutation analysis (n=34) detected PA driver mutations in 33 (97.1%): KCNJ5 (52.9%), CACNA1D (14.3%), ATP1A1 (6.1%), ATP2B2 (2.0%) and CTNNB1 (2.0%). Hybrid hormone levels were significantly higher in patients with KCNJ5 mutations compared to those with non-KCNJ5 mutation.

Conclusion: MTO PET/CT is non-inferior to AVS for diagnosing unilateral PA, and also identifies patients with unilateral surgically curable PA that are missed by AVS. Molecular imaging offers an alternative first-line subtyping modality for PA where available.