RT Journal Article SR Electronic T1 A randomised, factorial phase II study to determine the optimal dosing regimen for 68Ga-satoreotide trizoxetan as an imaging agent in patients with gastroenteropancreatic neuroendocrine tumours JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP jnumed.121.261936 DO 10.2967/jnumed.121.261936 A1 Irene Virgolini A1 Shadfar Bahri A1 Andreas Kjaer A1 Henning Gronbaek A1 Peter Iversen A1 Esben Andreas Carlsen A1 Mathias Loft A1 Ulrich Knigge A1 Johanna Maffey-Steffan A1 Christine Powell A1 Colin G. Miller A1 Thomas Rohban A1 Sandy McEwan A1 Johannes Czernin YR 2021 UL http://jnm.snmjournals.org/content/early/2021/07/02/jnumed.121.261936.abstract AB 68Ga-satoreotide trizoxetan is a novel somatostatin receptor antagonist associated with high sensitivity and reproducibility in neuroendocrine tumour (NET) detection and localisation. However, the optimal peptide mass and radioactivity ranges for 68Ga-satoreotide trizoxetan have not yet been established. We therefore aimed to determine its optimal dosing regimen in patients with metastatic gastroenteropancreatic NETs in a prospective, randomised, 2×3 factorial, multicentre, phase II study. Methods: Patients received 68Ga-satoreotide trizoxetan at a peptide mass of 5–20 µg on day 1 of the study and of 30–45 µg on day 16–22, at one of three gallium-68 radioactivity ranges (40–80, 100–140, or 160–200 MBq). Whole-body PET/CT imaging was performed 50–70 minutes after each injection. The primary endpoint was the detection rate of NET lesions imaged by 68Ga-satoreotide trizoxetan relative to contrast-enhanced CT (CECT) (for each of the six peptide mass/radioactivity range combinations). Results: Twenty-four patients were evaluated in the per-protocol analysis. The median number of lesions detected by 68Ga-satoreotide trizoxetan PET/CT or PET only was at least twice as high as the number of lesions detected by CECT across the six studied peptide mass dose/radioactivity range combinations. There were no differences between the two peptide mass ranges and between the three radioactivity ranges in the number of identified lesions. However, a trend towards a lower relative lesion count was noted in the liver for the 40–80 MBq range. No relationship was observed between the radioactivity range per patient’s body weight (MBq/kg) and the number of lesions detected by 68Ga-satoreotide trizoxetan. Median diagnostic sensitivity of 68Ga-satoreotide trizoxetan PET/CT, based on the number of lesions per patient, ranged from 85% to 87% across the different peptide mass and radioactivity ranges. Almost all reported adverse events were mild and self-limiting. Conclusion: A radioactivity of 100–200 MBq with a peptide mass up to 50 μg were confirmed as the optimal dosing regimen for 68Ga-satoreotide trizoxetan to be used in future phase III studies.