Characterization of Neuroblastic Tumors Using 18F-FDOPA PET

Neuroblastic tumors are childhood neoplasms that possess amino acid decarboxylase (AADC) activity and can theoretically be imaged by F-18-fluorodihydroxyphenylalanine (F-18-FDOPA) PET, a new diagnostic tool for neuroendocrine tumors. In this study, we explored the accuracy and clinical role of F-18-FDOPA PET in neuroblastic tumors. Methods: From 2008 to 2011, patients with tissue-proven neuroblastic tumors receiving F-18-FDOPA PET at initial diagnosis or during follow-ups were enrolled. The sensitivity and specificity of F-18-FDOPA PET were compared with those of I-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy and F-18-FDG PET, using tumor histology as the standard. The maximum standardized uptake value and tumor-to-liver uptake ratio on F-18-FDOPA PET were measured and correlated with AADC messenger RNA level in tumor tissue. Results: Fifty tumors from 34 patients, including 42 neuroblastic tumors and 8 lesions without viable tumor cells, were eligible for analysis. F-18-FDOPA PET successfully detected neuroblastic tumors of different histologic types in various anatomic sites, at a sensitivity of 97.6% (87.4%-99.9%) and a specificity of 87.5% (47.3%-99.7%). In tumors with concomitant studies, F-18-FDOPA PET demonstrated a higher sensitivity than I-123-MIBG scintigraphy (n = 18; P = 0.0455) or F-18-FDG PET (n = 46; P = 0.0455). Among the 18 tumors with concomitant I-123-MIBG scans, 4 tumors with viable cells were I-123-MIBG negative but were successfully detected by F-18-FDOPA PET. The tumor uptake of F-18-FDOPA significantly correlated with AADC expression (17 = 15 nonhepatic tumors; maximum standardized uptake value, P = 0.0002; tumor-to-liver uptake ratio, P < 0.0001). Conclusion: F-18-FDOPA PET showed high sensitivity and specificity in detecting and tracking neuroblastic tumors in this preliminary study with a small cohort of patients and might be complementary to I-123-MIBG scintigraphy and F-18-FDG PET. By correlating with AADC expression, F-18-FDOPA PET might serve as a useful imaging tool for the functional assessment of neuroblastic tumors.