RT Journal Article SR Electronic T1 In Vivo Instability of 177Lu-DOTATATE During Peptide Receptor Radionuclide Therapy JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1337 OP 1340 DO 10.2967/jnumed.119.237818 VO 61 IS 9 A1 Mark Lubberink A1 Helena Wilking A1 Amalia Öst A1 Ezgi Ilan A1 Mattias Sandström A1 Camilla Andersson A1 Katarzyna Fröss-Baron A1 Irina Velikyan A1 Anders Sundin YR 2020 UL http://jnm.snmjournals.org/content/61/9/1337.abstract AB Peptide receptor radiotherapy using 177Lu-labeled somatostatin ligand analogs is a well-established treatment for neuroendocrine tumors, with 177Lu-DOTATATE having acquired marketing authorization in Europe and the United States. The investigation of the pharmacokinetics of these radiopharmaceuticals in vivo in humans is crucial for personalized treatment management and understanding of treatment effects. Such an investigation requires input data on the in vivo stability of the radiopharmaceuticals in blood and plasma. The work presented here is devoted to the investigation of the in vivo stability of 177Lu-DOTATATE in humans affected by neuroendocrine tumors. Methods: Blood samples of 6 patients undergoing 177Lu-DOTATATE were taken at 0.5, 4, 24, and 96 h after injection. Analysis of metabolic stability was performed using high-performance liquid chromatography. Results: A fast metabolism of the radiopharmaceutical was observed, with the fraction of intact 177Lu-DOTATATE in plasma decreasing rapidly to 23% ± 5% (mean ± SD) at 24 h and 1.7% ±0. 9% at 96 h after injection. Conclusion: The in vivo stability of 177Lu-DOTATATE is much lower than previously assumed, with the major part of radioactivity in plasma consisting of 177Lu-labeled metabolites already at 24 h after injection.