Background : 123 I-MIBG imaging has several disadvantages: need for second-day imaging schedule, low resolution and imprecise, non-quantitative uptake measurements. 18 F-MFBG, a positron-emitting MIBG analog can potentially overcome these limitations. We present preliminary results of a first-in-human pilot study (Clinicaltrials.gov NCT02348749) evaluating pharmacokinetics and biodistribution of 18 F-MFBG.
Methods : Six patients (1 neuroblastoma; 5 paraganglioma/pheochromocytoma) received 10mCi/m218 F-MFBG intravenously followed by whole body (WB) PET imaging at three time points: ~30 min-1h, ~1-2 h and 3-4h post-injection (PI). Serial blood samples were collected 5 minutes-4 hours PI. WB and blood clearance rates, lesion uptake and radiation absorbed dose (RAD) for normal organs was analyzed using OLINDA software.
Results: No adverse events were encountered. WB clearance was mono-exponential with mean effective half-life (T1/2) of 1.8h. Blood clearance was bi-exponential with 0.2h (57 %) T1/2e for the rapid phase and 4.4h (43 %) for the slower phase. Renal excretion was rapid. Prominent activity noted in blood pool, liver and salivary glands, and mild activity in kidneys and spleen decreased with time. Median RAD estimates for urinary bladder, kidney and liver were 0.475, 0.125 and 0.139 cGy/mCi respectively with minimal activity noted in other organs. Mean±SD WB dose was 0.0311± 0.0202rad/mCi . Both skeletal and soft tissue lesions were visualized with high contrast as early as 0.5h PI, and best seen 3-4h PI. Mean±SD SUVMAX at 3-4h pi was 10.8±12.5 (range 1.1-80.7). Tumor to background ratios ranged from 1.35-36.2.
Conclusions: Preliminary data from this ongoing study shows that 18 F-MFBG imaging is safe, achievable on day of injection, has favorable biodistribution and kinetics with good targeting of lesions. 18 F-MFBG PET has the potential to be a better imaging modality than 123 I-MIBG gamma scan. Comparison with 123 I-MIBG scans is ongoing and further neuroblastoma patients are being studied.