Identification of Aldosterone-Producing Adrenal Adenomas Using [⁶⁸Ga]Ga-Pentixafor PET/CT in an Australian Cohort

Primary aldosteronism (PA) is the leading endocrine cause of hypertension. Subtyping is critical for identifying unilateral aldosterone-producing adenomas, which can be surgically resected. Adrenal vein sampling (AVS), the current standard for subtyping, is resource-intensive and invasive. We evaluated ⁶⁸Ga-pentixafor PET/CT as a noninvasive nuclear imaging alternative to AVS, assessing its diagnostic accuracy and acceptability compared with AVS in a multiethnic population. Methods: This prospective pilot study recruited adults with PA and an adrenal adenoma visible on CT. Unilateral disease was defined by a lateralization index (LI) of greater than or equal to 4 on AVS, performed before and after adrenocorticotropic hormone stimulation, confirmed by biochemical response after adrenalectomy. The PET LI was calculated using the SUV_max at 10 and 40 min after tracer injection. Participants with incomplete AVS or discordance between LIs before and after adrenocorticotropic hormone stimulation were excluded from the comparison of AVS and PET unless they underwent adrenalectomy. Receiver-operating-characteristic curves were constructed to assess the performance of different PET LIs for predicting PA subtype compared with AVS or surgical outcome. Results: ⁶⁸Ga-pentixafor PET/CT and AVS were performed in 34 patients (median age, 60 y). Five were excluded from the analysis, leaving 15 bilateral and 14 unilateral (9 left, 5 right) cases on the basis of AVS. The median PET LI at 10 min was 1.4 (interquartile range [IQR], 1.3-2.0) in the AVS-lateralized group and 1.1 (IQR, 1.1-1.3) in the nonlateralized group (P = 0.014); at 40 min, the median PET LI was 1.5 (IQR, 1.3-1.8) and 1.1 (IQR, 1.0-1.2), respectively (P = 0.014). A PET LI of 1.5 at 10 min achieved 100% specificity and 50% sensitivity. A PET LI of 1.4 at 40 min had higher sensitivity (64%) and lower specificity (87%). Survey responses indicated that PET/CT was faster, better tolerated, and the preferred test by 28 of 29 participants. Conclusion: ⁶⁸Ga-pentixafor PET/CT is well-tolerated and promising as a noninvasive tool for PA subtyping, demonstrating high specificity and moderate sensitivity for identifying aldosterone-producing adenomas.