Adrenal tracer uptake by 18 F-FDOPA PET/CT in patients with pheochromocytoma and controls.

Context: ¹⁸ F-FDOPA PET/CT accurately localizes pheochromocytoma in patients with an established biochemical diagnosis. However, cut-off ¹⁸ F-FDOPA levels of standardized uptake values (SUV _max ) for both normal adrenal glands and pheochromocytoma are lacking.
Objective: Objectives of this study were to determine (1) reference maximum standardized uptake values (SUVmax) for normal adrenal ¹⁸ F-DOPA tracer uptake and (2) the optimal diagnostic approach for pheochromocytoma localization by using ¹⁸ F-DOPA SUVmax across a series of cut-off points: the affected adrenal gland (inter-individual analysis), the difference in SUVmax between the affected adrenal gland and the contralateral normal adrenal gland (intra-individual analysis), or a combination of these two.
Patients and Methods: All patients with histologically confirmed pheochromocytoma diagnosed at our center between November 2009 and December 2017 were retrospectively analysed. Only those patients who underwent an ¹⁸ F-FDOPA PET/CT-scan for localization purposes before adrenalectomy were included for further analysis. The control group consisted of patients who underwent ¹⁸ F-FDOPA PET/CT for other indications and who had no genetic susceptibility for developing a pheochromocytoma. SUV _max of the volume of interest surrounding the adrenal glands was determined on EARL reconstructed images. Receiver operating characteristic (ROC) analysis was performed for adrenal gland SUV _max and intra-individual difference in SUV _max between affected and normal adrenal gland. In addition, binary logistic regression was performed for ROC analysis of the combined parameters.
Results: In total, 47 histologically confirmed pheochromocytomas were diagnosed in 45 patients, and 245 disease control patients were identified. In the control group, no statistical differences between the SUV _max of left and right adrenal glands were observed, and uptake values in both adrenal glands correlated significantly with each other (r = 0.865, p < 0.001). Median (range) adrenal gland SUV _max in pheochromocytomas and in the control group was 12 (2.6-50) and 2.9 (1.1-6.6), respectively (p < 0.001). ROC analysis revealed 93% sensitivity and 85% specificity at an SUV _max cut-off value of 4.1 (area under the curve (AUC) = 0.951), and 93% sensitivity and 96% specificity at an intra-individual SUV _max difference between the affected and normal adrenal gland of 1.0 (AUC = 0.992). The combination of both variables increased the AUC to 0.995.
Conclusions: ¹⁸ F-FDOPA PET/CT distinguishes pheochromocytoma from normal adrenal glands with the highest diagnostic accuracy when combining the SUVmax of the affected adrenal gland with the difference in SUV _max between affected and normal adrenal gland.