Abstract
BackgroundThe aim of the present study is to evaluate the kinetics and dosimetry of 64CuCl2 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 64CuCl2-PET/CT to detect PCa recurrence/metastases. Volumes of interest were manually drawn for each 64CuCl2 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.ResultsThe mean effective half-life of 64CuCl2 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 64CuCl2 SUVmax 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 64CuCl2 revealed that the calculated TBRmax 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 64CuCl2 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.ConclusionsDosimetry 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 64Cu internalization in the cell nucleus that seems related to the therapeutic effectiveness reported in preclinical studies.
Highlights
The aim of the present study is to evaluate the kinetics and dosimetry of 64CuCl2 in human prostate cancer (PCa) lesions
The analysis presented in this paper concerns PCa lesions with a diameter larger than 1 cm (0.52 mL) detected by 64CuCl2-PET/CT; 59 lesions in 35 patients were considered: 29 local recurrences, 21 lymph node metastases and 9 bone metastases
We found a significant difference in terms of PVEcorrected SUVmean and SUVmax evaluated 1 h after tracer injection between local and lymph node metastases and between local recurrences and bone metastases
Summary
The aim of the present study is to evaluate the kinetics and dosimetry of 64CuCl2 in human prostate cancer (PCa) lesions. The electron capture decay is followed by the emission of Auger electrons characterized by high linear energy transfer (LET); this is able to considerably increase the cytotoxic power of 64Cu, if the radioisotope is targeted near or within the cell nucleus. Because of these properties, 64Cu is described as the archetypal “theranostic” radioisotope, as it is potentially useful in PET/
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