68-Gallium-labelled ligand (DOTA-TOC) PET-CT for differentiating Adrenal Aldosterone-producing adenoma and non-secreting adenoma in primary aldosteronism

Background High-resolution computed tomography (CT) has increased the incidental detection rate of adrenal masses in recent years. Most of these cases are benign, although up to 10% are hormone-producing and require surgery. Distinguishing aldosterone-secreting from non-secreting adenomas based on conventional imaging remains challenging because of the lack of established imaging criteria for this purpose. Functional imaging of type 2 and 5 somatostatin receptors using a 68- Gallium-labelled ligand (DOTA-TOC) coupled with positron emission tomography (PET-CT) can help differentiate functionally active tumors, particularly aldosterone-producing adenomas (APA), from non-secreting adenomas. Aim This study aimed to evaluate the role of ⁶⁸Ga-DOTA-TOC PET/CT in the differential diagnosis of APAs and nonsecreting adrenal adenomas in patients with PA. Material and Methods Ten patients (7 men; mean age, 54 years [SD, 8]) with a confirmed diagnosis of primary aldosteronism (PA) based on the “Five corners” criteria (biochemical evidence of PA, Lateralized aldosterone secretion by AVS, detection of nodule by CT\MRI, biochemical correction after adrenalectomy, and CYP11B2-positive adenoma) were included in this retrospective study. Two expert radiologists in consensus delineated adrenal volumes of interest (VOI) using P-mod software on PET CT scans, assessing Metabolic Tumor Volume (MTV), SUV max, SUV mean, and SUV min in the early phase (at 3-6-9 minutes, post injection) and late phase (1h post injection). The mean SUVmean was also calculated. We used the contralateral adrenal gland to the adenoma, which was negative for AVS, as the control group. Results Culprit lesions showed higher MTV at 3 min (p = 0.003), elevated SUVmax at 6 min (p = 0.018) and 9 min (p = 0.004), and persistent uptake at 60 min (SUVmax, p = 0.043). The mean-SUVmean across all time points was significantly higher in the culprit lesions (p = 0.009), confirming sustained metabolic and receptor-mediated tracer accumulation in the functional adenomas. Conclusions ^68Ga-DOTA-TOC PET-CT demonstrates significant potential in differentiating APA from non-secreting adrenal adenomas. Functional adenomas showed higher metabolic activity and sustained tracer uptake over time, particularly elevated SUVmax and MTV values, comparedwith thosee of the contralateral control glands. These findings support the role of somatostatin receptor imaging as a reliable, noninvasive adjunct for detecting and characterizing functional adrenal lesions, improving diagnostic accuracy, and aiding in the targeted management of patients with PA.