Context: 18F-FDOPA PET/CT accurately localizes pheochromocytoma in patients with an established biochemical diagnosis. However, cut-off 18F-FDOPA levels of standardized uptake values (SUVmax) 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 18F-DOPA tracer uptake and (2) the optimal diagnostic approach for pheochromocytoma localization by using 18F-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 18F-FDOPA PET/CT-scan for localization purposes before adrenalectomy were included for further analysis. The control group consisted of patients who underwent 18F-FDOPA PET/CT for other indications and who had no genetic susceptibility for developing a pheochromocytoma. SUVmax 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 SUVmax and intra-individual difference in SUVmax 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 SUVmax 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 SUVmax 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 SUVmax cut-off value of 4.1 (area under the curve (AUC) = 0.951), and 93% sensitivity and 96% specificity at an intra-individual SUVmax 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: 18F-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 SUVmax between affected and normal adrenal gland.
Keywords: 18F-FDOPA; Adrenal glands; Normative data; Pheochromocytoma.