Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Purpose/Background:

Prostate-specific membrane antigen (PSMA) radioligand therapy has emerged as a promising
treatment for advanced prostate cancer. Prior to the administration of radioligand therapy, precise
assessment of PSMA expression and tumor localization is essential. Technetium-99m ( 99mTc)
imaging is cost-effective and widely available. This study presents the first experiences of using
[99mTc]TcO-ABX474 in patients with advanced prostate cancer, with the aim of providing valuable
insights into its clinical utility and feasibility.
Methods:
Patients with advanced prostate cancer, who were scheduled for PSMA radioligand therapy, were
referred to PSMA-Imaging. All patients underwent whole-body 99m Tc-PSMA ligand
single-photon emission computed tomography/computed tomography (SPECT/CT) imaging.
Qualitative and semi-quantitative assessments of [99mTc]TcO-ABX474 uptake were performed,
and the results were compared with 18F-PSMA-1007 PET/CT scans. Furthermore, ratios of at least
5 tumor lesions and salivary glands, spleen and kidneys to blood pool, muscle and liver were
calculated for each patient. PSMA tumor uptake for evaluation of radioligand therapy was assessed
using PROMISE V2 criteria.
Results:
In total 10 patients received a [99mTc]TcO-ABX474 SPECT/CT imaging prior to PSMA targeted
radioligand therapy. Dynamic imaging at 3 time points were performed in 4 patients. In 6 patients
image acquisition was performed starting 60 minutes after injection.
There was a washout of activity within normal tissue (blood pool, liver and salivary glands) from 10
to 60 and 180 Minutes after injection. The ratios of tumor lesions and the kidneys to normal tissue
uptake increased over the same period, whereas the ratios of the slivary glands and spleen decreased.
According to PROMISE V2 85, 10 and 5% of the measured lesions showed a PSMA Score of 3, 2
and 1, therefore 95% were eligible for PSMA radioligand therapy.
Conclusion:
This study represents the first clinical experiences with [99mTc]TcO-ABX474 imaging in patients
with advanced prostate cancer prior to PSMA targeted radioligand therapy. This non-invasive and
cost-effective imaging modality showed comparable results to imaging with PET-CT and
post-therapeutic SPECT/CT. It may therefore be suitable for use in the decision-making process for
radioligand therapy with 177Lu-PSMA.