Dual-time-point Cu-PSMA-617-PET/CT in patients suffering from prostate cancer.

Regardless of its high positron energy, Ga-68-labeled PSMA ligands have become standard of care in metabolic prostate cancer imaging. Cu-64, a radionuclide with a much longer half-life (12.7 h), is available for PSMA labeling allowing imaging much later than Ga-68. In this study, the diagnostic performance of Cu-64-labeled PSMA was compared between early and late scans. Sixteen men (median age: 70 y) with prostate cancer in different stages underwent Cu-64-PSMA-617-PET/CT 2 and 22 hours post tracer injection. Pathologic and physiologic uptakes were analyzed for both points of time. Pathologic tracer accumulations occurred in 12 patients. Five patients presented with pathologic uptake in 17 different lymph nodes, two patients showed pathologic bone uptake in nine lesions, and seven patients had pathologic PSMA uptake in eight prostatic lesions. Physiologic uptake of the renal parenchyma, urine bladder, and salivary glands decreased over time, while the physiologic uptake of liver and bowel increased. In the present study, Cu-64-PSMA-617-PET demonstrated to be feasible for imaging prostate cancer for both the primary tumor site and metastases. Later imaging showed no additional, clinically relevant benefit compared with the early scans. At least the investigated time points we chose did not vindicate the additional expenditure.