Expression of glutamate carboxypeptidase II in the glial tumor recurrence evaluated in vivo using radionuclide imaging.

Glutamate carboxypeptidase II (GCP), also known as prostate specific membrane antigen (PSMA) has been found to be expressed in glioma vasculature in in-vitro studies. GCP expression can be traced with the use of [68Ga]Ga-PSMA-11 PET/CT used routinely for prostate cancer imaging. The aim of this paper was to analyze GCP expression in the recurrent glial tumors in vivo. 34 patients (pts.) aged 44.5 ± 10.3 years with suspicion of recurrence of histologically confirmed glioma grade III (6 pts.) and grade IV (28 pts.) were included in the study. All patients underwent contrast-enhanced MR and [68Ga]Ga-PSMA-11 PET/CT. No radiopharmaceutical-related adverse events were noted. PET/CT was positive in all the areas suspected for recurrence at MR in all the patients. The recurrence was confirmed by histopathological examinations or follow-up imaging in all cases. The images showed a very low background activity of the normal brain. Median maximal standard uptake value (SUVmax) of the tumors was 6.5 (range 0.9-15.6) and mean standard uptake value (SUVmean) was 3.5 (range 0.9-7.5). Target-to-background (TBR) ratios varied between 15 and 1400 with a median of 152. Target-to-liver background ratios (TLR) ranged from 0.2 to 2.6, the median TLR was 1.3. No significant difference of the measured parameters was found between the subgroups according to the glioma grade. High GCP expression in the recurrent glioma was demonstrated in-vivo with the use of [68Ga]Ga-PSMA-11 PET/CT. As the treatment options in recurrent glioma are limited, this observation may open new therapeutic perspectives with the use of radiolabeled agents targeting the GCP.