Ga-68 pentixafor PET/CT as a novel diagnostic non-invasive tool for determining the subtype of primary aldosteronism: a case series

One of the most common causes of secondary hypertension is primary aldosteronism (PA). Aldosterone producing adenoma (APA) and bilateral adrenal hyperplasia (BAH) are the common causes of primary hyperaldosteronism. It is important to distinguish between APA and BAH in patients with proven PA since surgical intervention is advised for APA and medical management in the form of oral mineralocorticoid receptor antagonists for BAH. The current methods for subtyping PA are adrenal vein sampling (AVS) and CT. AVS is invasive and technically challenging, whereas CT has an accuracy of only 50-70%. Adrenal CXC chemokine receptor type 4 (CXCR4) expression is found in zona glomerulosa of adrenal cortex, and is significantly higher in APAs than in normal adrenal tissue as well as non-functional tumors. Pentixafor, a specific ligand for CXCR4 labelled with ⁶⁸Ga, proves beneficial in PA subtyping. This was a prospective study conducted at our institute from January 2023 to September 2023, consisting of 5 patients. Patients diagnosed with PA underwent Ga-68 Pentixafor PET/CT. Dose of 0.05 mCi/kg was administered intravenously and PET/CT whole body scan was acquired after 1 hour. Adrenal nodule with focal increased tracer uptake was considered to be APA. Diffuse increased tracer uptake was considered to be BAH. In case of APA, the SUVmax was obtained by drawing ROI on the nodule showing focal tracer uptake, whereas in BAH, ROI was drawn on both the adrenals to obtain SUVmax. Ga-68 Pentixafor PET/CT is a promising non- invasive method which can be an alternative or an adjunct for AVS when it is inconclusive/non-diagnostic/contraindicated. It has a proven sensitivity and specificity for detecting primary aldosteronism