18F-DOPA PET provides superior imaging for pheochromocytoma

6-[F-18]Fluoro-L-Dihydroxyphenylalanine Positron Emission Tomography Is Superior to Conventional Imaging with ¹²³I-Metaiodobenzylguanidine Scintigraphy, Computer Tomography, and Magnetic Resonance Imaging in Localizing Tumors Causing Catecholamine Excess.

Helle-Brit Fiebrich, Adrienne H. Brouwers, Michiel N. Kerstens, Milan E. J. Pijl, Ido P. Kema, Johan R. de Jong, Pieter L. Jager, Philip H. Elsinga, Rudi A. J. O. Dierckx, Jacqueline E. van der Wal, Wim J. Sluiter, Elisabeth G. E. de Vries and Thera P. Links.

The Journal of Clinical Endocrinology & Metabolism Vol. 94, No. 10 3922-3930

Abstract:
Context: Catecholamine excess is rare, but symptoms may be life threatening.

Objective: The objective of the study was to investigate the sensitivity of 6-[F-18]fluoro-L-dihydroxyphenylalanine positron emission tomography (¹⁸F-DOPA PET), compared with ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) scintigraphy and computer tomography (CT)/magnetic resonance imaging (MRI) for tumor localization in patients with catecholamine excess.

Design and Setting: All consecutive patients with catecholamine excess visiting the University Medical Center Groningen, Groningen, The Netherlands, between March 2003 and January 2008 were eligible.

Patients: Forty-eight patients were included. The final diagnosis was pheochromocytoma in 40, adrenal hyperplasia in two, paraganglioma in two, ganglioneuroma in one, and unknown in three.

Main Outcome Measures: Sensitivities and discordancy between ¹⁸F-DOPA PET, ¹²³I-MIBG, and CT or MRI were analyzed for individual patients and lesions. Metanephrines and 3-methoxytyramine in plasma and urine and uptake of ¹⁸F-DOPA with PET were measured to determine the whole-body metabolic burden and correlated with biochemical tumor activity. The gold standard was a composite reference standard.

Results: ¹⁸F-DOPA PET showed lesions in 43 patients, ¹²³I-MIBG in 31, and CT/MRI in 32. Patient-based sensitivity for ¹⁸F-DOPA PET, ¹²³I-MIBG, and CT/MRI was 90, 65, and 67% (P <> for ¹⁸F-DOPA PET vs. both ¹²³I-MIBG and CT/MRI, P = 1.0 ¹²³I-MIBG vs. CT/MRI). Lesion-based sensitivities were 73, 48, and 44% (P <>18F-DOPA PET vs. both ¹²³I-MIBG and CT/MRI, P = 0.51 ¹²³I-MIBG vs. CT/MRI). The combination of ¹⁸F-DOPA PET with CT/MRI was superior to ¹²³I-MIBG with CT/MRI (93 vs. 76%, P <> ¹⁸F-DOPA PET correlated with plasma normetanephrine (r = 0.82), urinary normetanephrine (r = 0.84), and metanephrine (r = 0.57).

Conclusion: To localize tumors causing catecholamine excess, ¹⁸F-DOPA PET is superior to ¹²³I-MIBG scintigraphy and CT/MRI.

Comments:
Localizing catecholamine secreting tumors can be notably difficult. This study looked at several imaging modalities in 48 patients with known catecholamine excess. Imaging included 18F-DOPA PET, 123I-MIBG, CT, and MRI.

The highest sensitivity for detecting lesions was 18F-DOPA Pet with CT/MRI which had a 94% sensitivity. 18F-DOPA PET alone had a 72% sensitivity. In contrast, 123I-MIBG with CT/MRI had only a 76% sensitivity. CT/MRI alone was noted to miss mainly adrenal lesions less than 2 cm.

The final histology in patients who received surgery was Pheochromocytoma in 40 patients, adrenal hyperplasia in 2, paraganglioma in 2, ganglioneuroma in 1. 3 remained unknown because no lesions were detected.

At least from this report it appears that combination 18F-DOPA with CT or MRI would be the best way to localize tumor mass in patients with catecholamine excess.