Diagnostic Value of Early F-18-FDOPA PET-CT for Initial Staging of Neuroblastoma: A Comparison Study with Delay F-18-FDOPA PET-CT and I-123-MIBG Scintigraphy/SPECT-CT

157 Objectives: Neuroblastoma is the most common extracranial tumors in children, and about half of patients have metastatic disease at presentation (1, 2). I-123-MIBG has been recognized as a radiopharmaceutical of choice in neuroblastoma assessment (3, 4). In recent years, promising diagnostic results are reported by F-18-FDOPA PET-CT after 60-90 min of radiopharmaceutical injection (delay F-18-FDOPA PET-CT) (5, 6). Early F-18-FDOPA PET-CT (3-30 min scan after radiopharmaceutical injection) showed better diagnostic performance in medullary thyroid cancer and brain tumor (7, 8), however, it has not been studied in neuroblastoma until now. Our aim was to evaluate the diagnostic value of early F-18-FDOPA PET-CT in neuroblastoma for initial staging and compare with that of delay F-18-FDOPA PET-CT and I-123-MIBG scintigraphy/SPECT-CT. Methods: Final eleven neuroblastoma patients (M:F = 5:6, age = 3.3±2.7 yr) who performed early, delay F-18-FDOPA PET-CT and I-123-MIBG scintigraphy/SPECT-CT as an initial staging work-up were retrospectively enrolled. Early and delay F-18-FDOPA PET-CT scan were performed at 7.2±6.0 min and 63.5±6.0 min, after 3 MBq/kg of F-18-FDOPA injection, respectively. I-123-MIBG scintigraphy was done at 4 hr and 24 hr, after 5.18 MBq/kg of I-123-MIBG injection, and additional SPECT-CT was acquired at chest and/or abdomen area (primary tumor area). Images were evaluated by two nuclear medicine physicians in the blinded condition. When the disagreement occurs, the third nuclear medicine physician made a final decision. We performed a lesion-based and a scan-based analysis and calculated diagnostic performance (9, 10). In addition, maximum standardized uptake value (maxSUV) on early and delay F-18-FDOPA PET-CT was compared on both early and delay scan true positive lesions. The standard of reference was based on clinical, histologic and radiologic (whole body MRI, chest and abdomen CT) data (10). Results: On lesion-based analysis, early F-18-FDOPA PET/CT showed sensitivity 95.2% (100/105) and accuracy 87.4% (111/127), which was better than that of delay F-18-FDOPA PET/CT and I-123-MIBG scintigraphy/SPECT-CT with statistical significance (all P <0.001). On scan-based analysis, early F-18-DOPA PET/CT demonstrated sensitivity 96.6% (28/29) and accuracy 94.1% (32/34), with statistical significance and significant trend in comparison with delay F-18-FDOPA PET/CT and I-123-MIBG scintigraphy (P=0.011 and 0.078). No significant difference was found in terms of specificity. Comparison of maxSUV on both early and delay F-18-FDOPA PET-CT true positive lesions revealed significantly higher maxSUV on early scan (early maxSUV vs. delay maxSUV = 5.2±2.7 vs. 3.3±2.1; P <0.001). Conclusions: Early F-18-FDOPA PET-CT displayed higher sensitivity and accuracy than delay F-18-FDOPA PET-CT and I-123-MIBG scintigraphy/SPECT-CT. Furthermore, higher maxSUV on early scan than that of delay scan in true positive lesions means that early F-18-FDOPA PET-CT demonstrated more discrete uptake. We suggest that early F-18-FDOPA PET-CT as a new opportunity for initial staging of neuroblastoma.