Biodistribution and first clinical results of 18 F-SiFAlin-TATE PET: a novel 18 F-labeled somatostatin analog for imaging of neuroendocrine tumors

PET/CT using Ga-labeled somatostatin analogs (SSA) targeting somatostatin receptors (SSR) on the cell surface of well-differentiated neuroendocrine tumors (NET) represents the clinical reference standard for imaging. However, economic and logistic challenges of the Ge/ Ga generator-based approach have disadvantages over F-labeled compounds. Here, we present the first in-human data of F-SiFAlin-TATE, a novel F-labeled, SSR-targeting peptide. The aim was to compare the intra-individual biodistribution, tumor uptake, and image quality of F-SiFAlin-TATE to the clinical reference standard Ga-DOTA-TOC. Thirteen patients with NET staged with both Ga-DOTA-TOC and F-SiFAlin-TATE PET/CT have been included in this retrospective analysis. We compared the biodistribution in normal organs and tumor uptake of NET lesions by SUVmean and SUVmax measurement for tracers. Additionally mean and max tumor-to-liver (TLR) and tumor-to-spleen ratios (TSR) have been calculated by division of SUVmean and SUVmax of tumor lesions by the SUVmean of the liver and spleen, respectively. Additionally, image quality was visually rated by 5 blinded readers and an intra-class correlation (ICC) analysis on inter-observer agreement has been performed. Compared with Ga-DOTA-TOC, the biodistribution of F-SiFAlin-TATE showed somewhat higher, however, statistically not significant higher uptake in the liver, spleen, and adrenal glands. Significantly higher uptake was observed in the kidneys. Tumor uptake was higher in most tumor lesions with significantly higher uptake in common metastatic sites of NET including the liver (SUVmax 18.8 ± 8.4 vs. 12.8 ± 5.6; p