Biodistribution and radiation dosimetry of [99mTc]Tc-N4-BTG in patients with biochemical recurrence of prostate cancer

Andreas Rinscheid; Alexander Gäble; Georgine Wienand; Alexander Dierks; Malte Kircher; Thomas Günther; Marianne Patt; Ralph A Bundschuh; Constantin Lapa; Christian H Pfob

doi:10.1186/s13550-024-01105-6

Biodistribution and radiation dosimetry of [^99mTc]Tc-N4-BTG in patients with biochemical recurrence of prostate cancer

EJNMMI Res. 2024 Apr 26;14(1):42. doi: 10.1186/s13550-024-01105-6.

Authors

Andreas Rinscheid^#¹, Alexander Gäble^#², Georgine Wienand², Alexander Dierks², Malte Kircher², Thomas Günther³, Marianne Patt^{2

4}, Ralph A Bundschuh^{2

4}, Constantin Lapa^#^{5

6}, Christian H Pfob^#^{2

4}

Affiliations

¹ Medical Physics and Radiation Protection, University Hospital Augsburg, Augsburg, Germany.
² Nuclear Medicine, Faculty of Medicine, University of Augsburg, Augsburg, Germany.
³ Molecular Imaging Program at Stanford, Department of Radiology, Stanford University, Palo Alto, CA, USA.
⁴ Bavarian Cancer Research Center (BZKF), Erlangen, Bavaria, Germany.
⁵ Nuclear Medicine, Faculty of Medicine, University of Augsburg, Augsburg, Germany. Constantin.Lapa@uk-augsburg.de.
⁶ Bavarian Cancer Research Center (BZKF), Erlangen, Bavaria, Germany. Constantin.Lapa@uk-augsburg.de.

^# Contributed equally.

Abstract

Background: In patients with prostate cancer (PCa), imaging with gastrin-releasing peptide receptor (GRPR) ligands is an alternative to PSMA-targeted tracers, particularly if PSMA expression is low or absent. [^99mTc]Tc-N4-BTG is a newly developed GRPR-directed probe for conventional scintigraphy and single photon emission computed tomography (SPECT) imaging. The current study aims to investigate the safety, biodistribution and dosimetry of [^99mTc]Tc-N4-BTG in patients with biochemical recurrence (BCR) of PCa.

Results: No adverse pharmacologic effects were observed. Injection of [^99mTc]Tc-N4-BTG resulted in an effective dose of 0.0027 ± 0.0002 mSv/MBq. The urinary bladder was the critical organ with the highest mean absorbed dose of 0.028 ± 0.001 mGy/MBq, followed by the pancreas with 0.0043 ± 0.0015 mGy/MBq, osteogenic cells with 0.0039 ± 0.0005 mGy/MBq, the kidneys with 0.0034 ± 0.0003 mGy/MBq, and the liver with 0.0019 ± 0.0004 mGy/MBq, respectively. No focal tracer uptake suggestive of PCa recurrence could be revealed for any of the patients.

Conclusion: [^99mTc]Tc-N4-BTG appears to be a safe diagnostic agent. Compared to GRPR-targeted PET tracers, this ^99mTc-labelled SPECT agent could contribute to a broader application and better availability of this novel approach. Further research to assess its clinical value is warranted.

Keywords: Bombesin; GRPR; PET; Prostate cancer; Theranostics.