[F-18]metafluorobenzylguanidine (MFBG) PET-CT vs. [I-123]metaiodobenzylguanidine (MIBG) imaging in neuroblastoma patients

Aim/Introduction: [18F]metafuorobenzylguanidine (MFBG) is a new PET tracer for imaging of neuroblastoma. Compared to standard [123I]metaiodobenzylguanidine (MIBG) imaging, MFBG PET-CT ofers the advantages of faster acquisition, single-day imaging, no need for thyroid protection and higher resolution PET imaging. The aim of this study was to evaluate the feasibility and diagnostic performance of MFBG PET-CT compared to MIBG imaging in neuroblastoma patients. Materials and Methods: In this prospective pilot study from July 2020 to May 2021, we aimed to perform paired MFBG PET-CT and MIBG scans. All paediatric neuroblastoma patients referred for standard MIBG imaging were eligible for inclusion. MIBG imaging consisted of administration of 4 MBq/kg [123I]MIBG (range 80-300 MBq), followed by next-day whole-body planar scintigraphy (including focused feld-ofview SPECT-CT). Patients underwent additional MFBG PETCT within two weeks, which consisted of administration of 2 MBq/kg [18F]MFBG (range 21-166 MBq), followed by a totalbody PET-CT at 60 minutes post-injection. For comparison of skeletal involvement on paired scans, the SIOPEN score was used. Results: Eighteen paired MFBG and MIBG scans were performed in a total of twelve patients (11/12 stage M). No adverse events related to MFBG injection were observed. The majority (8/10) of patients who required sedation for MIBG scanning, were able to undergo MFBG PET-CT without sedation. MFBG had a lower estimated efective dose than MIBG (median 0.84 mSv [IQR 0.76-1.22] vs. 3.22 mSv [IQR 3.03-3.83], respectively). In almost all paired scans, MFBG PET-CT detected equal or more skeletal disease compared to MIBG imaging. On patient-based analysis, MFBG PETCT detected a higher total SIOPEN score in 67% (12/18), an equal score in 28% (5/18), and a lower score in 5% (1/18) of the scans. On skeletal segment-based analysis, MFBG PET-CT detected a higher SIOPEN score in 27% (58/216), an equal score in 70% (153/216), and a lower score in 3% (5/216) of the segments. In 67% (12/18) of the paired scans MFBG PET-CT detected additional lesions in 38 skeletal segments that were negative on MIBG imaging. Conclusion: MFBG PET-CT is considered a safe and feasible imaging method in paediatric neuroblastoma patients. MFBG PET-CT has many practical advantages and provides excellent imaging quality at a lower radiation exposure. Preliminary results indicate that MFBG PET-CT may have higher tumour detection capability compared to MIBG imaging. In almost all cases (95%), MFBG PET-CT detected equal or more skeletal disease. MFBG PET-CT has the potential to replace MIBG imaging in neuroblastoma patients.