TY - JOUR T1 - In Vivo Instability of <sup>177</sup>Lu-DOTATATE During Peptide Receptor Radionuclide Therapy JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1337 LP - 1340 DO - 10.2967/jnumed.119.237818 VL - 61 IS - 9 AU - Mark Lubberink AU - Helena Wilking AU - Amalia Öst AU - Ezgi Ilan AU - Mattias Sandström AU - Camilla Andersson AU - Katarzyna Fröss-Baron AU - Irina Velikyan AU - Anders Sundin Y1 - 2020/09/01 UR - http://jnm.snmjournals.org/content/61/9/1337.abstract N2 - 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. ER -