18F-FDOPA PET and PET/CT Accurately Localize Pheochromocytomas

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Abstract
Successful treatment of pheochromocytoma requires accurate diagnosis and localization of tumors. Herein, we investigated the accuracy of PET using 3,4-dihydroxy-6-18F-fluoro-phenylalanine (18F-FDOPA), an amino acid transporter substrate, as an independent marker for detection of benign and malignant pheochromocytomas. Methods: The study comprised 25 consecutive patients (9 men, 16 women) whose median age was 51 y (range, 25–68 y), with known or suspected pheochromocytoma. Eleven patients underwent standardized 18F-FDOPA PET and 14 patients underwent 18F-FDOPA PET/CT studies, with a median of 511 MBq of 18F-FDOPA (range, 206–625 MBq). Two readers, unaware of the reports of other imaging studies and clinical data, analyzed all scans visually and quantitatively (maximum standardized uptake value [SUVmax] and maximum transverse diameter). Histology and long-term clinical follow-up served as the gold standard. Correlation between SUVmax of tumors and biochemical markers was evaluated. SUVmax of the benign and malignant tumors was compared. Results: Seventeen patients underwent surgery. Histology confirmed pheochromocytoma or paraganglioma in 11 cases (8 adrenal, including 2 malignant tumors, and 3 extraadrenal, including 1 malignant tumor). The diagnosis of pheochromocytoma was established by follow-up in 2 additional patients (1 adrenal and 1 unknown location) and ruled out in 6 patients. Visual analysis detected and localized pheochromocytoma in 11 of 13 patients without false-positive results (sensitivity, 84.6%; specificity, 100%; accuracy, 92%). These lesions had an SUVmax of 2.3–34.9 (median, 8.3). Evaluation of the false-negative cases revealed a 13 × 5 mm lesion with an SUVmax of 1.96 in 1 case; no lesion was localized in the second case using multiple additional modalities. Spearman nonparametric analysis did not show statistically significant correlation between SUVmax of the tumors and biochemical markers. The Mann–Whitney nonparametric test did not demonstrate a statistically significant difference between the SUVmax of 18F-FDOPA in malignant and benign tumors. Conclusion: 18F-FDOPA PET and PET/CT are highly sensitive and specific tools that can provide additional independent information for diagnosis and localization of benign and malignant pheochromocytomas.