PT  - JOURNAL ARTICLE
AU  - Richard P. Baum
AU  - Aviral Singh
AU  - Harshad R. Kulkarni
AU  - Peter Bernhardt
AU  - Tobias Rydén
AU  - Christiane Schuchardt
AU  - Nadezda Gracheva
AU  - Pascal V. Grundler
AU  - Ulli Köster
AU  - Dirk Müller
AU  - Michael Pröhl
AU  - Jan Rijn Zeevaart
AU  - Roger Schibli
AU  - Nicholas P. van der Meulen
AU  - Cristina Müller
TI  - First-in-Humans Application of <sup>161</sup>Tb: A Feasibility Study Using <sup>161</sup>Tb-DOTATOC
AID  - 10.2967/jnumed.120.258376
DP  - 2021 Oct 01
TA  - Journal of Nuclear Medicine
PG  - 1391--1397
VI  - 62
IP  - 10
4099  - http://jnm.snmjournals.org/content/62/10/1391.short
4100  - http://jnm.snmjournals.org/content/62/10/1391.full
SO  - J Nucl Med2021 Oct 01; 62
AB  - 161Tb has decay properties similar to those of 177Lu but, additionally, emits a substantial number of conversion and Auger electrons. The aim of this study was to apply 161Tb in a clinical setting and to investigate the feasibility of visualizing the physiologic and tumor biodistributions of 161Tb-DOTATOC. Methods: 161Tb was shipped from Paul Scherrer Institute, Villigen-PSI, Switzerland, to Zentralklinik Bad Berka, Bad Berka, Germany, where it was used for the radiolabeling of DOTATOC. In 2 separate studies, 596 and 1,300 MBq of 161Tb-DOTATOC were administered to a 35-y-old male patient with a metastatic, well-differentiated, nonfunctional malignant paraganglioma and a 70-y-old male patient with a metastatic, functional neuroendocrine neoplasm of the pancreatic tail, respectively. Whole-body planar γ-scintigraphy images were acquired over a period of several days for dosimetry calculations. SPECT/CT images were reconstructed using a recently established protocol and visually analyzed. Patients were observed for adverse events after the application of 161Tb-DOTATOC. Results: The radiolabeling of DOTATOC with 161Tb was readily achieved with a high radiochemical purity suitable for patient application. Planar images and dosimetry provided the expected time-dependent biodistribution of 161Tb-DOTATOC in the liver, kidneys, spleen, and urinary bladder. SPECT/CT images were of high quality and visualized even small metastases in bones and liver. The application of 161Tb-DOTATOC was well tolerated, and no related adverse events were reported. Conclusion: This study demonstrated the feasibility of imaging even small metastases after the injection of relatively low activities of 161Tb-DOTATOC using γ-scintigraphy and SPECT/CT. On the basis of this essential first step in translating 161Tb to clinics, further efforts will be directed toward the application of 161Tb for therapeutic purposes.