Molecular imaging non-inferior to adrenal vein sampling in detecting aldosterone-producing adrenal adenomas

1. In this prospective within-patient trial, [¹¹C]metomidate ([¹¹C]MTO) positron emission tomography-computed tomography was non-inferior to adrenal vein sampling in identifying aldosterone-producing adrenal adenomas.

2. [¹¹C]MTO showed high agreement with its analogue, para-chloro-2-[¹⁸F]fluoroethyletomidate ([¹⁸F]CETO).

Evidence Rating Level: 2 (Good)

Study Rundown: Although adrenal vein sampling (AVS) is the main method for diagnosing unilateral primary aldosteronism (PA), it remains unavailable in most clinical settings and can be challenging even for experienced operators. Molecular imaging using [¹¹C]MTO, a precursor for a selective ligand for aldosterone synthase, was developed as a non-invasive alternative that does not depend on operator skill. Following promising proof-of-concept results, this study was designed to determine the accuracy of [¹¹C]MTO positron emission tomography-computed tomography (PET CT) compared with AVS in identifying aldosterone-producing adrenal adenomas (APAs) as well as predicting biochemical and clinical outcomes after their removal. Of all study participants, [¹¹C]MTO graded slightly more than half as having high probability of unilateral PA, while slightly less than half were graded as such by AVS. Over ninety percent of patients who underwent surgery had complete or partial biochemical success, and over eighty percent of patients had complete or partial clinical success. Compared with AVS, [¹¹C]MTO was not deemed to be superior in predicting outcomes, although it also did not meet the threshold for inferiority. When compared with [¹⁸F]CETO, an analogue with a longer half-life, [¹¹C]MTO showed concordance in over ninety percent of patients. The generalizability of this study was limited by the fact that the accuracy of [¹¹C]MTO could only be assessed among patients who underwent surgery, that real-life patients would be unlikely to receive both [¹¹C]MTO and AVS, ansud that there was a lack of randomization in comparing surgical and medical management. Nonetheless, this study showed that [¹¹C]MTO could be a useful alternative to AVS in diagnosing unilateral PA.

Click to read this study in AIM

Related Reading: Evaluation of the Sensitivity and Specificity of 11C-Metomidate Positron Emission Tomography (PET)-CT for Lateralizing Aldosterone Secretion by Conn’s Adenomas

In-Depth [prospective cohort]: This prospective within-patient trial compared the accuracy of molecular imaging versus AVS in identifying APAs and predicting biochemical and clinical outcomes following surgery in patients with unilateral PA. Included patients were adults with a focal abnormality on imaging consistent with an adrenal adenoma. A total of 169 participants were included in this study, 113 (66.8%) of whom were male. The median age was 53 years; 59.8% of participants identified as White, 28.4% as Black, and 11.2% as Asian. [¹¹C]MTO determined 89 (52.7%) participants as having high probability of unilateral PA, compared with 78 (46.2%) participants determined by AVS. Based on these findings, surgery was recommended for 100 (59.1%) participants. Biochemical outcome data were available for 91 of these participants; 84 (92.3%) achieved at least partial biochemical success, with 80 (87.9%) achieving complete success. The difference in accuracy between [¹¹C]MTO and AVS was 8.5% (95% CI, -5.6% to 22.2%) in determining at least partial biochemical success and 8.5% (95% CI, -5.8% to 22.4%) in determining complete success. Clinical outcome data were available for 93 participants; 76 (82%) participants achieved at least partial clinical success, with 26 (28%) achieving complete success. The difference in accuracy between [¹¹C]MTO and AVS was 4.2% (95% CI, -10.2% to 18.3%) in determining at least partial clinical success and -2.1% (95% CI, -16.4% to 12.4%) in determining complete success. No confidence intervals crossed the -17% threshold for inferiority, suggesting that [¹¹C]MTO was similarly effective versus AVS. The last 31 participants to be enrolled underwent both [¹¹C]MTO and [¹⁸F]CETO. [¹¹C]MTO was concordant with [¹⁸F]CETO for 29 (93.5%) participants; [¹¹C]MTO detected high probability of unilateral PA in 18 (58.1%) participants while [¹⁸F]CETO detected high probability in 17 (54.8%) participants (κ = 0.85 [95% CI, 0.68 to 1.00]). Overall, this study showed that [¹¹C]MTO was non-inferior to AVS regarding accuracy of identifying APAs and assessing biochemical and clinical outcomes following surgery.

Image: PD

©2025 2 Minute Medicine, Inc. All rights reserved. No works may be reproduced without expressed written consent from 2 Minute Medicine, Inc. Inquire about licensing here. No article should be construed as medical advice and is not intended as such by the authors or by 2 Minute Medicine, Inc.