RT Journal Article
SR Electronic
T1 The Effects of Carbidopa on Uptake of 6-<sup>18</sup>F-Fluoro-<span class="sc">l</span>-DOPA in PET of Pheochromocytoma and Extraadrenal Abdominal Paraganglioma
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1599
OP 1606
DO 10.2967/jnumed.107.042721
VO 48
IS 10
A1 Henri J.L.M. Timmers
A1 Mohiuddin Hadi
A1 Jorge A. Carrasquillo
A1 Clara C. Chen
A1 Lucia Martiniova
A1 Millie Whatley
A1 Alexander Ling
A1 Graeme Eisenhofer
A1 Karen T. Adams
A1 Karel Pacak
YR 2007
UL http://jnm.snmjournals.org/content/48/10/1599.abstract
AB 6-18F-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.