Positron Emission Tomography (PET) Imaging of Prostate Cancer with a Gastrin Releasing Peptide Receptor Antagonist - from Mice to Men

Ex vivo studies have shown that the gastrin releasing peptide receptor (GRPr) is overexpressed on almost all primary prostate cancers, making it a promising target for prostate cancer imaging and targeted radiotherapy. Methods: Biodistribution, dosimetry and tumor uptake of the GRPr antagonist Cu-64-CB-TE2A-AR06 [(Cu-64-4,l l-bis(carboxymethyl)-1,4,8,l l-tetraazabicyclo(6.6.2) hexadecane)-PEG(4)-D-Phe-Gln-TrpAla- Val-Gly-His-Sta-LeuNH(2)] were studied by PET/CT in four patients with newly diagnosed prostate cancer (T lc-T2b, Gleason 6-7). Results: No adverse events were observed after injection of Cu-64-CB-TE2A-AR06. Three of four tumors were visualized with high contrast [ tumor-to-prostate ratio > 4 at 4 hours (h) post injection (p. i.)], one small tumor (T l c, < 5% tumor on biopsy specimens) showed moderate contrast (tumor-to-prostate ratio at 4 h: l 9). Radioactivity was cleared by the kidneys and only the pancreas demonstrated significant accumulation of radioactivity, which rapidly decreased over time. Conclusion: 64Cu-CB-TE2A-AR06 shows very favorable characteristics for imaging prostate cancer. Future studies evaluating 64Cu-CB-TE2A-AR06 PET/CT for prostate cancer detection, staging, active surveillance, and radiation treatment planning are necessary.