Scandium and terbium radionuclides for radiotheranostics: current state of development towards clinical application

Cristina Müller, Katharina A Domnanich, Christoph A Umbricht, Nicholas P van der Meulen
2018 British Journal of Radiology  
Cite this article as: Müller C, Domnanich KA, Umbricht CA, van der Meulen NP. Scandium and terbium radionuclides for radiotheranostics: current state of development towards clinical application. Br J Radiol 2018; 91: 20180074. absTracT Currently, different radiometals are in use for imaging and therapy in nuclear medicine: 68 Ga and 111 In are examples of nuclides for positron emission tomography (PET) and single photon emission computed tomography (SPECT), respectively, while 177 Lu and 225 Ac
more » ... are used for β − -and α-radionuclide therapy. The application of diagnostic and therapeutic radionuclides of the same element (radioisotopes) would utilize chemically-identical radiopharmaceuticals for imaging and subsequent treatment, thereby enabling the radiotheranostic concept. There are two elements which are of particular interest in this regard: Scandium and Terbium. Scandium presents three radioisotopes for theranostic application. 43 Sc (T 1/2 = 3.9 h) and 44 Sc (T 1/2 = 4.0 h) can both be used for PET, while 47 Sc (T 1/2 = 3.35 d) is the therapeutic match-also suitable for SPECT. Currently, 44 Sc is most advanced in terms of production, as well as with pre-clinical investigations, and has already been employed in proof-of-concept studies in patients. Even though the production of 43 Sc may be more challenging, it would be advantageous due to the absence of high-energetic γ-ray emission. The development of 47 Sc is still in its infancy, however, its therapeutic potential has been demonstrated preclinically. Terbium is unique in that it represents four medically-interesting radioisotopes. 155 Tb (T 1/2 = 5.32 d) and 152 Tb (T 1/2 = 17.5 h) can be used for SPECT and PET, respectively. Both radioisotopes were produced and tested preclinically. 152 Tb has been the first Tb isotope that was tested (as 152 Tb-DO-TATOC) in a patient. Both radionuclides may be of interest for dosimetry purposes prior to the application of radiolanthanide therapy. The decay properties of 161 Tb (T 1/2 = 6.89 d) are similar to 177 Lu, but the coemission of Auger electrons make it attractive for a combined β − /Auger electron therapy, which was shown to be effective in preclinical experiments. 149 Tb (T 1/2 = 4.1 h) has been proposed for targeted α-therapy with the possibility of PET imaging. In terms of production, 161 Tb and 155 Tb are most promising to be made available at the large quantities suitable for future clinical translation. This review article is dedicated to the production routes, the methods of separating the radioisotopes from the target material, preclinical investigations and clinical proof-of-concept studies of Sc and Tb radionuclides. The availability, challenges of production and first (pre)clinical application, as well as the potential of these novel radionuclides for future application in nuclear medicine, are discussed. 2 of 13 birpublications.org/bjr Br J Radiol;91:20180074 BJR Müller et al 3 of 13 birpublications.org/bjr Br J Radiol;91:20180074 BJR Review article: Scandium and terbium radionuclides for radiotheranostics obtained after irradiation of the Ca target for 1 h, however, 44m Sc, 47
doi:10.1259/bjr.20180074 pmid:29658792 fatcat:kscfcnfifjcobpq7s5ajzomzra