Biokinetic and dosimetric aspects of CuCl in human prostate cancer: possible theranostic implications.

BACKGROUND

The aim of the present study is to evaluate the kinetics and dosimetry of CuCl in human prostate cancer (PCa) lesions. We prospectively evaluated 50 PCa patients with biochemical relapse after surgery or external beam radiation therapy. All patients underwent CuCl-PET/CT to detect PCa recurrence/metastases. Volumes of interest were manually drawn for each CuCl avid PCa lesion with a diameter > 1 cm on mpMRI in each patient. Time-activity curves for all lesions were obtained. The effective and biological half-life and the standard uptake values (SUVs) were calculated. Tumour/background ratio (TBR) curves as a function of time were considered. Finally, the absorbed dose per lesion was estimated.

RESULTS

The mean effective half-life of CuCl calculated in the lymph nodes (10.2 ± 1.7 h) was significantly higher than in local relapses (8.8 ± 1.1 h) and similar to that seen in bone metastases (9.0 ± 0.4 h). The mean CuCl SUV calculated 1 h after tracer injection was significantly higher in the lymph nodes (6.8 ± 4.3) and bone metastases (6.8 ± 2.9) than in local relapses (4.7 ± 2.4). TBR mean curve of CuCl revealed that the calculated TBR value was 5.0, 7.0, and 6.2 in local relapse and lymph node and bone metastases, respectively, and it was achieved about 1 h after CuCl injection. The mean absorbed dose of the PCa lesions per administrated activity was 6.00E-2 ± 4.74E-2mGy/MBq. Indeed, for an administered activity of 3.7 GBq, the mean dose absorbed by the lesion would be 0.22 Gy.

CONCLUSIONS

Dosimetry showed that the dose absorbed by PCa recurrences/metastases per administrated activity was low. The dosimetric study performed does not take into account the possible therapeutic effect of the Auger electrons. Clinical trials are needed to evaluate Cu internalization in the cell nucleus that seems related to the therapeutic effectiveness reported in preclinical studies.