[ 18 F] MFBG PET imaging: biodistribution, pharmacokinetics, and comparison with [ 123 I] MIBG in neural crest tumour patients

Purpose Despite its limitations, [ 123 I]MIBG scintigraphy has been the standard for human norepinephrine transporter (hNET) imaging for several decades. Recently, [ 18 F]MFBG has emerged as a promising PET alternative. This prospective trial aimed to evaluate safety, biodistribution, tumour lesion pharmacokinetics, and lesion targeting of [ 18 F]MFBG and perform a head-to-head comparison with [ 123 I]MIBG in neural crest tumour patients. Methods Six neural crest tumour patients (4 phaeochromocytoma, 1 paraganglioma, 1 neuroblastoma) with a recent routine clinical [ 123 I]MIBG scintigraphy (interval: − 37–75 days) were included. Adult patients ( n = 5) underwent a 30-min dynamic PET, followed by 3 whole-body PET/CT scans at 60, 120, and 180 min after injection of 4 MBq/kg [ 18 F]MFBG. One minor participant underwent a single whole-body PET/CT at 60 min after administration of 2 MBq/kg [ 18 F]MFBG. Normal organ uptake (SUV mean ) and lesion uptake (SUV max ; tumour-to-background ratio (TBR)) were measured. Regional distribution volumes ( V T ) were estimated using a Logan graphical analysis in up to 6 lesions per patient. A lesion-by-lesion analysis was performed to compare detection ratios (DR), i.e. fraction of detected lesions, between [ 18 F]MFBG and [ 123 I]MIBG. Results [ 18 F]MFBG was safe and well tolerated. Its biodistribution was overall similar to that of [ 123 I]MIBG, with prominent uptake in the salivary glands, liver, left ventricle wall and adrenals, and mainly urinary excretion. In the phaeochromocytoma subgroup, the median V T was 37.4 mL/cm 3 (range: 18.0–144.8) with an excellent correlation between V T and SUV mean at all 3 time points ( R 2 : 0.92–0.94). Mean lesion SUV max and TBR at 1 h after injection were 19.3 ± 10.7 and 23.6 ± 8.4, respectively. All lesions detected with [ 123 I]MIBG were also observed with [ 18 F]MFBG. The mean DR with [ 123 I]MIBG was significantly lower than with [ 18 F]MFBG (61.0% ± 26.7% vs. 99.8% ± 0.5% at 1 h; p = 0.043). Conclusion [ 18 F]MFBG is a promising hNET imaging agent with favourable imaging characteristics and improved lesion targeting compared with [ 123 I]MIBG scintigraphy. Trial registration Clinicaltrials.gov : NCT04258592 (Registered: 06 February 2020), EudraCT: 2019-003872-37A.