Evaluation of adrenal masses using ¹⁸F-FDOPA PET/CT in patients suspected with pheochromocytoma

Objective Pheochromocytomas (PHEOs) are chromaffin cell-derived adrenal tumors. 6-[¹⁸F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (¹⁸F-FDOPA) is a radiotracer taken up in neuroendocrine chromaffin cells via the L-type amino-acid transporter. ¹⁸F-FDOPA is useful in patients with PHEO. However, more information about the use of ¹⁸F-FDOPA PET/CT scan is needed. Thus, the current study investigated various PET parameters on preoperative ¹⁸F-FDOPA PET/CT scan. Methods The ¹⁸F-FDOPA PET/CT scan findings of 29 patients who underwent adrenalectomy after PET/ CT scans were evaluated according to their pathologic diagnosis. Thereafter, the patients were classified under different risk groups which were compared based on the Grading System for Adrenal Pheochromocytoma and Paraganglioma (GAPP). Results In terms of histopathologic results after surgery, 24 patients presented with PHEO. The remaining 5 patients were diagnosed with adrenal cortical adenomas or adrenal medullary hyperplasia. The maximum standardized uptake value, mean standardized uptake value, tumor-to-liver ratio, and tumor-to-contralateral adrenal gland ratio of PHEOs on preoperative ¹⁸F-FDOPA PET/CT scan were higher than those of other tumors. The metabolic tumor volume (MTV) and total lesion uptake of PHEOs in the intermediate-risk group (n = 19) were higher than those in the low-risk group (n = 5). The MTV and total lesion uptake were significantly correlated with the GAPP score. Conclusion Preoperative ¹⁸F-FDOPA PET/CT is helpful to identifying PHEOs. In addition, imaging interpretation using the standardized uptake value of the suspected tumor or the tumor-to-liver/contralateral adrenal gland ratio can be effective. The metabolic parameters of PHEOs are positively correlated with the GAPP score.