123I-MIBG scintigraphy/SPECT versus 18F-FDG PET in paediatric neuroblastoma

Purpose To analyse different uptake patterns in I-123-MIBG scintigraphy/SPECT imaging and F-18-FDG PET in paediatric neuroblastoma patients. Methods We compared 23 I-123-MIBG scintigraphy scans and 23 F-18-FDG PET scans (mean interval 10 days) in 19 patients with a suspected neuroblastic tumour (16 neuroblastoma, 1 ganglioneuroblastoma, 1 ganglioneuroma and 1 opsomyoclonus syndrome). SPECT images of the abdomen or other tumour-affected regions were available in all patients. Indications for F-18-FDG PET were a I-123-MIBG-negative tumour, a discrepancy in I-123-MIBG uptake compared to the morphological imaging or imaging results inconsistent with clinical findings. A lesion was found by I-123-MIBG scintigraphy and/or F-18-FDG PET and/or morphological imaging. Results A total of 58 suspicious lesions (mean lesion diameter 3.8 cm) were evaluated and 18 were confirmed by histology and 40 by clinical follow-up. The sensitivities of I-123-MIBG scintigraphy and F-18-FDG PET were 50% and 78% and the specificities were 75% and 92%, respectively. False-positive results (three I-123-MIBG scintigraphy, one F-18-FDG PET) were due to physiological uptake or posttherapy changes. False-negative results (23 I-123-MIBG scintigraphy, 10 F-18-FDG PET) were due to low uptake and small lesion size. Combined I-123-MIBG scintigraphy/F-18-FDG PET imaging showed the highest sensitivity of 85%. In 34 lesions the I-123-MIBG scintigraphy and morphological imaging findings were discrepant. F-18-FDG PET correctly identified 32 of the discrepant findings. Two bone/bone marrow metastases were missed by F-18-FDG PET. Conclusion I-123-MIBG scintigraphy and F-18-FDG PET showed noticeable differences in their uptake patterns. F-18-FDG PET was more sensitive and specific for the detection of neuroblastoma lesions. Our findings suggest that a F-18-FDG PET scan may be useful in the event of discrepant or inconclusive findings on I-123-MIBG scintigraphy/SPECT and morphological imaging.