Conclusion
68Ga-pentixafor PET/CT imaging exhibits great potential for noninvasive functional lateralization and characterization in patients with adrenocortical masses.
Methods
Sixty-four patients who had benign adrenal masses on CT were retrospectively included in our study. All patients underwent 68Ga-pentixafor PET/CT, and 56 of these patients subsequently underwent adrenalectomy. The subtypes of 81 adrenal tumors, including 14 nonfunctioning adrenal nodules, 4 cortisol-producing adenomas, 41 aldosterone-producing adenomas, 5 cases of suspected unilateral adrenal hyperplasia, 15 cases of idiopathic aldosterone hyperplasia, and 2 pheochromocytomas, were determined by histology or follow-up evaluations. The diagnostic efficiency of functional lateralization was calculated by visual analysis. Semiquantitative parameters of these lesions, including SUVmax, the ratio of lesional SUVmax to normal liver SUVmean (LLR), and the ratio of lesional SUVmax to contralateral adrenal tissue SUVmean (LCR), were also calculated. Dynamic analysis was also performed on 15 patients. In addition, clinical outcomes were assessed and compared in patients who underwent adrenalectomy.
Results
The sensitivity and specificity of 68Ga-pentixafor PET for functional lateralization in patients with adrenocortical lesions were 97.8% (45/46) and 87.5% (14/16), respectively. The 2 pheochromocytoma lesions had lower pentixafor uptake than the normal adrenal glands. Functioning (active) adrenocortical adenomas showed an elevated SUVmax of 16.3 ± 7.9, in comparison to 4.4 ± 1.7 in nonfunctioning (inactive) adenomas and 5.5 ± 2.7 in hyperplasia lesions (P < 0.0001). To identify active adrenocortical adenomas, a cutoff of 7.1 for SUVmax showed a sensitivity of 90.9% and a specificity of 85.3% (area under receiver-operating-characteristic curve, 0.96; P < 0.0001); a cutoff of 2.5 for LLR showed a sensitivity of 95.5% and a specificity of 88.2% (area under receiver-operating-characteristic curve, 0.97; P < 0.0001); and a cutoff of 2.4 for LCR showed a sensitivity of 88.6% and a specificity of 91.8% (area under receiver-operating-characteristic curve, 0.95; P < 0.0001). The graphical influx rate constant of active adrenocortical adenomas was significantly higher than that of inactive adenomas. Uptake values for 68Ga-pentixafor were significantly higher in patients with preferable outcomes (cured/improved) (SUVmax, 15.5 ± 8.0; LLR, 6.5 ± 4.3; LCR, 6.2 ± 5.0) than in patients with nonpreferable outcomes (no improvement) (SUVmax, 4.2 ± 0.5; LLR, 1.3 ± 0.2; LCR, 1.5 ± 0.6; all P < 0.0001).