[68Ga]Ga-PSMA-11 PET imaging as a predictor for absorbed doses in organs at risk and small lesions in [177Lu]Lu-PSMA-617 treatment

Steffie M. B. Peters*, Regina Hofferber, Bastiaan M. Prive, Maarten de Bakker, Martin Gotthardt, Marcel Janssen, Frank de Lange, Constantijn H. J. Muselaers, Niven Mehra, J. Alfred Witjes, Pedro F. Costa, James Nagarajah, Mark W. Konijnenberg, Walter Jentzen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Introduction Patient eligibility for [177Lu]Lu-PSMA therapy remains a challenge, with only 40-60% response rate when patient selection is done based on the lesion uptake (SUV) on [68Ga]Ga-PSMA-PET/CT. Prediction of absorbed dose based on this pre-treatment scan could improve patient selection and help to individualize treatment by maximizing the absorbed dose to target lesions while adhering to the threshold doses for the organs at risk (kidneys, salivary glands, and liver). Methods Ten patients with low-volume hormone-sensitive prostate cancer received a pre-therapeutic [68Ga]Ga-PSMA-11 PET/CT, followed by 3 GBq [177Lu]Lu-PSMA-617 therapy. Intra-therapeutically, SPECT/CT was acquired at 1, 24, 48, 72, and 168 h. Absorbed dose in organs and lesions (n = 22) was determined according to the MIRD scheme. Absorbed dose prediction based on [68Ga]Ga-PSMA-PET/CT was performed using tracer uptake at 1 h post-injection and the mean tissue effective half-life on SPECT. Predicted PET/actual SPECT absorbed dose ratios were determined for each target volume. Results PET/SPECT absorbed dose ratio was 1.01 +/- 0.21, 1.10 +/- 0.15, 1.20 +/- 0.34, and 1.11 +/- 0.29 for kidneys (using a 2.2 scaling factor), liver, submandibular, and parotid glands, respectively. While a large inter-patient variation in lesion kinetics was observed, PET/SPECT absorbed dose ratio was 1.3 +/- 0.7 (range: 0.4-2.7, correlation coefficient r = 0.69, p < 0.01). Conclusion A single time point [68Ga]Ga-PSMA-PET scan can be used to predict the absorbed dose of [177Lu]Lu-PSMA therapy to organs, and (to a limited extent) to lesions. This strategy facilitates in treatment management and could increase the personalization of [177Lu]Lu-PSMA therapy.
Original languageEnglish
Pages (from-to)1101-1112
Number of pages12
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Volume49
Issue number4
Early online dateOct 2021
DOIs
Publication statusPublished - Mar 2022

Bibliographical note

Funding Information:
W. Jentzen received research funding from Siemens Healthineers. Partial financial support was received from the Radboud Oncology Foundation and the Dutch Prostate Cancer Foundation.

Publisher Copyright:
© 2021, The Author(s).

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