⁶⁸Ga-PSMA dynamic PET/CT imaging of prostate cancer: Tracer distribution patterns and pharmacokinetics

Objectives The advent of ⁶⁸Ga-PSMA PET/CT constitutes a promising step towards the improvement of prostate cancer (PC) diagnostics. Aim of our study is to assess the distribution patterns and pharmacokinetics of ⁶⁸Ga-PSMA in patients suffering from PC.

Methods 36 patients with PC (14 primary PC, 22 pre-treated PC) were enrolled in the study. All patients underwent dynamic PET/CT (dPET/CT) scanning (60 min) of the pelvis as well as whole body PET/CT studies with ⁶⁸Ga-PSMA. The evaluation of dPET/CT studies was based on qualitative evaluation, SUV calculation, and quantitative analysis based on a 2-tissue compartment model and a non-compartmental approach.

Results ⁶⁸Ga-PSMA PET/CTs images were of excellent quality and without any artifacts. In 29 patients at least one lesion was detected, while 6 pre-treated patients were ⁶⁸Ga-PSMA-negative. One patient demonstrated no tracer uptake neither in tumor nor in tissues where physiological uptake is expected. A total of 187 lesions were detected (13 primary PCS, 5 recurrent PCs, 169 lymph node and osseous metastases). PC-associated lesions (primary PC, recurrent PC, metastatic sites) revealed a mean SUV_average of 13.3 (median=9.1) and a mean SUV_max of 21.2 (median=17.0). The absolute ⁶⁸Ga-PSMA quantitative values derived from dPET/CT studies of the pelvis, after application of two-tissue compartment modelling were K₁=0.25 (median=0.16), k₃=0.33 (median=0.27), influx=0.15 (median=0.10), FD=1.26 (median=1.30). No difference between primary and metastatic sites, regarding kinetic parameters’ values, was found.

Conclusions The pharmacokinetics and distribution of ⁶⁸Ga-PSMA were analyzed in 36 PC patients by means of dynamic and whole body PET/CT. PC-related lesions demonstrated significantly higher SUVs and kinetic parameters’ values than respective reference tissue values (p<0.01).