Endocrine Abstracts

Introduction: Primary aldosteronism (PA) is a form of secondary hypertension, affecting 2.4% of the hypertensive population. It is caused by autonomous overproduction of aldosterone by either a unilateral aldosterone-producing adenoma (APA) or by bilateral adrenal hyperplasia (BAH). Subtyping is crucial, because PA is cured by adrenalectomy in APA and is treated by medication in BAH. The reference standard in subtyping PA is adrenal vein sampling (AVS). However, it is invasive, costly, has limited availability and is accompanied by risk of serious complications. We propose employing the positron emission tomography-computed tomography (PET-CT) tracer [⁶⁸Ga]Ga-PentixaFor, which has high accuracy in detecting APAs in PA. The goal of this study is to determine concordance of [⁶⁸Ga]Ga-PentixaFor PET-CT and AVS. Secondary outcomes are timepoint for scanning, criteria for lateralization and biochemical and clinical success after adrenalectomy.

Methods: This study is part of a two-step diagnostic trial. We included patients with PA from two academic centers, confirmed by an intravenous salt-loading test. Patients underwent AVS and [⁶⁸Ga]Ga-PentixaFor PET-CT. Patients were treated based on the AVS results. A dynamic scan was performed to determine the optimal timepoint for scanning in the first 6 patients. The main outcome was the concordance of AVS and [⁶⁸Ga]Ga-PentixaFor PET-CT. The SUVmax was used to determine lateralization in [⁶⁸Ga]Ga-PentixaFor PET-CT. The PASO criteria for clinical outcomes were used to assess the surgical outcomes at 3 and 6 months post-surgery.

Results: Twenty-five patients underwent adrenal vein sampling and a [⁶⁸Ga]Ga-PentixaFor PET-CT. The optimal timepoint of scanning was 1h post-injection. Using a cut-off of SUV-max-ratio of 1.4 we reached a concordance of 68%, sensitivity of 60% and specificity of 80%. Using a Bayesian prediction model, the predicted-concordance was: 67% (CI80%=54–78). At 3 months post-surgery, complete biochemical success was observed in 100% (10/10) of patients and in 83% (5/6) at the 6-month mark. Clinical success rates were noted to be 70% (7/10) at 3 months and 67% (4/6) at 6 months.

Conclusion: [⁶⁸Ga]Ga-PentixaFor PET-CT is an imaging modality with high concordance with AVS. With these results we have sufficient evidence to proceed to step-2: A randomized controlled diagnostic trial, where patients will be randomized in [⁶⁸Ga]Ga-PentixaFor PET-CT or AVS.