Sensitivity of 6-[F-18]fluoro-L-dihydroxyphenylalanine positron emission tomography for localizing tumors causing catecholamine excess

Abstract

11064 Background: Positron emission tomography (PET) using the catecholamine precursor 6-[F-18]fluoro-L-dihydroxyphenylalanine ((18)F-DOPA) has emerged as promising technique to localize tumors with catecholamine excess. This study investigated the sensitivity of (18)F-DOPA PET, compared to (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy and computer tomography (CT)/ magnetic resonance imaging (MRI) in patients with catecholamine excess. METHODS: In a single center prospective study (18)F-DOPA PET was compared to (123)I-MIBG and CT/MRI in patients with catecholamine excess. The performance of each imaging modality was analyzed for individual patients and individual lesions. (18)F-DOPA PET, (123)I-MIBG, and CT/MRI were compared using a composite reference standard derived from all available imaging, clinical and histological information. Sensitivities were calculated and discordance between imaging techniques was compared. (18)F-DOPA PET uptake was measured to determine whole body metabolic burden. Correlations between (18)F-DOPA PET imaging and biochemical data were evaluated. RESULTS: 48 patients were included. The tumor localization was found in 45 patients, 43 with (18)F-DOPA PET, 31 with (123)I-MIBG and 32 with CT/MRI, resulting with surgery in final diagnosis of pheochromocytoma in 40, adrenal hyperplasia in 2, paraganglioma in 2, ganglioneuroma in 1 and 3 unknown (as yet no lesion detected). Per patient based analysis showed sensitivities for (18)F-DOPA PET, (123)I-MIBG and CT/MRI of 90, 65 and 67% (P<.01 (18)F-DOPA PET vs (123)I-MIBG, P<.01 (18)F-DOPA PET vs CT/MRI, P=1.0 (123)I-MIBG vs CT/MRI). Corresponding sensitivities in the lesion based analysis were 73, 48 and 44%, respectively (P<.001 for both (18)F-DOPA PET vs (123)I-MIBG and vs CT/MRI, P=.51 (123)I-MIBG vs CT/MRI). The (8)F-DOPA PET+CT/MRI combination was superior to (123)I-MIBG+CT/MRI (93 vs 76%, P<.001) Whole body metabolic burden measured with (18)F-DOPA PET correlated with plasma free normetanephrine (r=.82) and 24h urinary total normetanephrine (r=.84) and metanephrine (r=.57). CONCLUSIONS: The sensitivity of (18)F-DOPA PET to localize tumors with catecholamine excess is superior to either (123)I-MIBG scintigraphy or CT/MRI. No significant financial relationships to disclose.