RT Journal Article SR Electronic T1 Biokinetics and Dosimetry of 177Lu-Pentixather JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 754 OP 760 DO 10.2967/jnumed.121.262295 VO 63 IS 5 A1 Heribert Hänscheid A1 Andreas Schirbel A1 Philipp Hartrampf A1 Sabrina Kraus A1 Rudolf A. Werner A1 Hermann Einsele A1 Hans-Jürgen Wester A1 Michael Lassmann A1 Martin Kortüm A1 Andreas K. Buck YR 2022 UL http://jnm.snmjournals.org/content/63/5/754.abstract AB The chemokine receptor 4 (CXCR4), which is overexpressed in many solid and hematologic malignancies, can be targeted for radiopeptide therapy via the antagonist pentixather. The biokinetics and dosimetry of 177Lu-pentixather and 90Y-pentixather were analyzed in this study. Methods: This retrospective study was a standardized reevaluation of data collected for treatment planning. Nineteen patients with complete sets of planar whole-body scans over at least 4 d and a single SPECT/CT scan after administration of 200 MBq of 177Lu-pentixather were included. Kinetics were measured in the whole body, in tissues with activity retention, and in 10 individuals in the blood. Time-integrated activity coefficients and tissue-absorbed doses were derived. Results: Increased uptake of pentixather was observed in the kidneys, liver, spleen, and bone marrow, inducing respective median absorbed doses of 0.91 Gy (range, 0.38–3.47 Gy), 0.71 Gy (range, 0.39–1.17 Gy), 0.58 Gy (range, 0.34–2.26 Gy), and 0.47 Gy (range, 0.14–2.33 Gy) per GBq of 177Lu-pentixather and 3.75 Gy (range, 1.48–12.2 Gy), 1.61 Gy (range, 1.14–2.97 Gy), 1.66 Gy (range, 0.97–6.69 Gy), and 1.06 Gy (range, 0.27–4.45 Gy) per GBq of 90Y-pentixather. In most tissues, activity increased during the first day after the administration of 177Lu-pentixather and afterward decayed with mean effective half-lives of 41 ± 10 h (range, 24–64 h) in the kidneys and median half-lives of 109, 86, and 92 h in the liver, spleen, and bone marrow, respectively. Maximum uptake per kidney was 2.2% ± 1.0% (range, 0.6%–5.1%). In organs showing no specific uptake, absorbed doses exceeding 0.3 Gy/GBq of 90Y-pentixather were estimated for the urinary bladder and for tissues adjacent to accumulating organs such as the adrenal glands, bone surface, and gallbladder. Dose estimates for tumors and extramedullary lesions ranged from 1.5 to 18.2 Gy/GBq of 90Y-pentixather. Conclusion: In patients with hematologic neoplasms, absorbed doses calculated for bone marrow and extramedullary lesions are sufficient to be effective as an adjunct to high-dose chemotherapies before stem cell transplantation.