The Influence of Specific Activity on the Biodistribution of [18F]SiTATE: A Retrospective Analysis of Clinical PET Data

Ziel/Aim: [¹⁸F]SiTATE is a novel somatostatin receptor-targeting PET-agent with potential clinical advantages based on its F18-label consisting in large batch production, longer half-life and the potential to be shipped over larger distances. In this retrospective analysis, we investigated whether the time between synthesis and injection and the resulting decrease in specific activity affects its normal organ uptake.

Methodik/Methods: A total of 30 patients with neuroendocrine tumors were retrospectively selected based on the specific activity of injected [¹⁸F]SiTATE and sub-grouped in patients receiving high (mean value, 118,5 MBq/µg, n=15) versus low specific activity (mean value, 31,9 MBq/µg, n=15). SUVmean was determined within standardized isocontour volumes of interest with 50% of the SUVmax and a diameter of 30 mm in the following organs: thyroid gland, submandibular gland, lung, liver, kidney, adrenal gland, spleen, pancreas (uncinate process), urinary bladder, prostate, muscle, bone and blood pool. Differences in mean SUVmean values were compared using a student t-test.

Ergebnisse/Results: In the sub-group of patients with low specific activity the median SUV mean in the thyroid gland, submandibular gland, lung, liver, kidney, adrenal gland, spleen, pancreas, urinary bladder, prostate, muscle, bone and blood pool were 3.3, 1.86, 0.32, 6.05, 17.52, 19.74, 39.48, 6.51, 8.93, 4.21, 0.76, 1.19, 1.19, respectively. In the sub-group of patients with low specific activity the median SUV mean in the thyroid gland, submandibular gland, lung, liver, kidney, adrenal gland, spleen, pancreas, urinary bladder, prostate, muscle, bone and blood pool were 3.46, 2.07, 0.31, 7.50, 16.10, 22.1, 41.46, 7.50, 12.80, 4.96, 0.85, 1.17, 1.37. Of all regions tracer uptake in the musculature and blood pool activity were slightly but statistically significantly lower in the low-specific-activity group (median SUVmean: 0.76 vs. 0.85, p=0.027; 1.19 vs. 1.37, p=0.033, respectively). No other statistically significant differences were found for normal organs.

Schlussfolgerungen/Conclusion: A 4-fold decrease in specific activity has only minor effects on the biodistribution of [¹⁸F]SiTATE. These findings suggest that ¹⁸F-labeled somatostatin receptor ligands can be centrally produced and shipped to PET clinics in a similar way to [¹⁸F]FDG.

Publikationsverlauf

Artikel online veröffentlicht:
12. März 2025