Replacing Lu-177 with Tb-161 in DOTA-TATE and PSMA-617 therapy: potential dosimetric implications for activity selection

Frederik A Verburg; Erik de Blois; Stijn Koolen; Mark W Konijnenberg

doi:10.1186/s40658-023-00589-w

Replacing Lu-177 with Tb-161 in DOTA-TATE and PSMA-617 therapy: potential dosimetric implications for activity selection

EJNMMI Phys. 2023 Nov 10;10(1):69. doi: 10.1186/s40658-023-00589-w.

Authors

Frederik A Verburg¹, Erik de Blois², Stijn Koolen^{2

3

4}, Mark W Konijnenberg^{2

5}

Affiliations

¹ Department of Radiology and Nuclear Medicine, Erasmus Medical Center, Dr Molewaterplein 40, 3015 GD, Rotterdam, The Netherlands. f.verburg@erasmusmc.nl.
² Department of Radiology and Nuclear Medicine, Erasmus Medical Center, Dr Molewaterplein 40, 3015 GD, Rotterdam, The Netherlands.
³ Department of Hospital Pharmacy, Erasmus MC, Rotterdam, The Netherlands.
⁴ Department of Medical Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
⁵ Department of Radiology and Nuclear Medicine, Radboud UMC, Nijmegen, The Netherlands.

Abstract

Aim: To explore the dosimetric effect of substituting Lu-177 with Tb-161 in targeted radionuclide therapy (TRT) using the registered tracers DOTA-TATE and PSMA-617.

Methods: Using established kinetic data for [¹⁷⁷Lu]Lu-DOTA-TATE and [¹⁷⁷Lu]Lu-PSMA-617, radiation absorbed doses to typical tumour lesion as well as non-target tissues ([¹⁷⁷Lu]Lu-DOTA-TATE: kidneys, spleen and liver, [¹⁷⁷Lu]Lu-PSMA-617: kidneys, liver and salivary glands) were calculated for Lu-177 and Tb-161.

Results: For both DOTA-TATE and PSMA-617, the substitution of Lu-177 with Tb-161 results in an increase in the delivered dose per unit of activity to tumour tissue by 40%. If an equivalent non-target delivered dose is strived for in order not to increase toxicity, based on kidney absorbed dose, 7400 MBq Lu-177 per cycle should be substituted with 5400 MBq Tb-161 for DOTA-TATE and 5300 MBq of Tb-161 for PSMA-617.

Conclusion: When substituting Lu-177 with Tb-161, activity conversion is necessary in order not to exceed non-target dose limits.

Keywords: Dosimetry; Radionuclide therapy; Terbium-161; [177Lu]Lu-DOTA-TATE; [177Lu]Lu-PSMA-617.