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Pheochromocytoma and Extraadrenal Abdominal Paraganglioma

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Pheochromocytoma and Extraadrenal Abdominal Paraganglioma

Henri J.L.M. Timmers1,2, Mohiuddin Hadi3, Jorge A. Carrasquillo3, Clara C. Chen3, Lucia Martiniova1, Millie Whatley3, Alexander Ling4, Graeme Eisenhofer5, Karen T. Adams1 and Karel Pacak1

 

1 Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; 2 Department of Endocrinology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; 3 Nuclear Medicine Department, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland; 4 Department of Diagnostic Radiology, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland; and 5 Clinical Neurocardiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland

 

Correspondence: For correspondence or reprints contact: Karel Pacak, MD, PhD, DSc, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, 10 Center Dr., Bldg. 10, CRC, RM 1-E 3140, MSC 1109, Bethesda, MD 20892-1109. E-mail: karel@mail.nih.gov 6-18

 

F-fluoro-L-3,4-dihydroxyphenylalanine (18F-DOPA) PET is a useful tool for the detection of certain neuroendocrine tumors, especially with the preadministration of carbidopa, an inhibitor of DOPA decarboxylase. Whether carbidopa also improves 18F-DOPA PET of adrenal pheochromocytomas and extraadrenal paragangliomas is unknown. The aim of this study was to investigate the sensitivity of 18F-DOPA PET in the detection of paraganglioma and its metastatic lesions and to evaluate whether tracer uptake by the tumors is enhanced by carbidopa.

 

Methods: Two patients with nonmetastatic adrenal pheochromocytoma, and 9 patients with extraadrenal abdominal paraganglioma (1 nonmetastatic, 8 metastatic), underwent whole-body CT, MRI, baseline 18F-DOPA PET, and 18F-DOPA PET with oral preadministration of 200 mg of carbidopa. The dynamics of tracer uptake by these lesions and the physiologic distribution of 18F-DOPA in normal tissues were recorded.

Results: Seventy-eight lesions were detected by CT or MRI, 54 by baseline 18F-DOPA PET (P = 0.0022 vs. CT/MRI), and 57 by 18F-DOPA PET plus carbidopa (P = 0.0075 vs. CT/MRI, not statistically significant vs. baseline). In reference to findings on CT and MRI, the sensitivities of baseline 18F-DOPA PET were 47.4% for lesions and 55.6% for positive body regions, versus 50.0% (lesions) and 66.7% (regions) for 18F-DOPA PET plus carbidopa (neither is statistically significant vs. baseline). Compared with baseline, carbidopa detected additional lesions in 3 (27%) of 11 patients. Carbidopa increased the mean (?SD) peak standardized uptake value in index tumor lesions from 6.4 ? 3.9 to 9.1 ? 5.6 (P = 0.037). Pancreatic physiologic 18F-DOPA uptake, which may mask adrenal pheochromocytoma, is blocked by carbidopa.

 

Conclusion: Carbidopa enhances the sensitivity of 18F-DOPA PET for adrenal pheochromocytomas and extraadrenal abdominal paragangliomas by increasing the tumor-to-background ratio of tracer uptake. The sensitivity of 18F-DOPA PET for metastases of paraganglioma appears to be limited.

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