⁶⁴CuCl₂ PET/CT in Prostate Cancer Relapse

Our objective was to evaluate the biodistribution, kinetics, and radiation dosimetry of ⁶⁴CuCl₂ in humans and to assess the ability of ⁶⁴CuCl₂ PET/CT to detect prostate cancer (PCa) recurrence in patients with biochemical relapse. Methods: We prospectively evaluated 50 PCa patients with biochemical relapse after surgery or external-beam radiation therapy. All patients underwent ⁶⁴CuCl₂ PET/CT, ¹⁸F-choline PET/CT, and multiparametric MRI within 15 d of each other. Experienced readers interpreted the images, and the detection rate (DR) of each imaging modality was calculated. Histopathology, when available; clinical or laboratory response; and multidisciplinary follow-up were used to confirm the site of disease. In parallel, biodistribution, kinetics of the lesions, and radiation dosimetry of ⁶⁴CuCl₂ were evaluated. Results: From a dosimetric point of view, an administered dose of 200 MBq for ⁶⁴CuCl₂ translated into a 5.7-mSv effective dose. Unlike ¹⁸F-choline, ⁶⁴CuCl₂ was not excreted or accumulated in the urinary tract, thus allowing thorough pelvic exploration. The maximum ⁶⁴CuCl₂ uptake at the sites of PCa relapse was observed 1 h after tracer injection. In our cohort, ⁶⁴CuCl₂ PET/CT proved positive in 41 of 50 patients, with an overall DR of 82%. The DRs of ¹⁸F-choline PET/CT and multiparametric MRI were 56% and 74%, respectively. The difference between the DRs of ⁶⁴CuCl₂ PET/CT and ¹⁸F-choline PET/CT was statistically significant (P < 0.001). Interestingly, on considering prostate-specific antigen (PSA) value, ⁶⁴CuCl₂ PET/CT had a higher DR than ¹⁸F-choline PET/CT in patients with a PSA of less than 1 ng/mL. Conclusion: The biodistribution of ⁶⁴CuCl₂ is more suitable than that of ¹⁸F-choline for exploring the pelvis and prostatic bed. The ⁶⁴CuCl₂ effective dose is like those of other established PET tracers. In patients with biochemical relapse and a low PSA level, ⁶⁴CuCl₂ PET/CT shows a significantly higher DR than ¹⁸F-choline PET/CT.