Ga-68 PSMA PET/CT in recurrent high-grade gliomas: evaluating PSMA expression in vivo

We planned this prospective study to evaluate PSMA expression in recurrent high-grade gliomas (rHGG), including anaplastic astrocytoma and glioblastoma using Glu-NH-CO-NH-Lys-(Ahx)-[Ga-68 (HBED-CC)]- (Ga-68 PSMA) positron emission tomography (PET), with its theranostic potential in mind.

This was a prospective study enrolling patients with clinical and MRI evidence of rHGG on follow-up. Three treated cases of HGG with RN on MRI were also included as negative controls. Abnormal tracer accumulation in the brain parenchyma, more than the contralateral hemisphere was interpreted as positive study. For semiquantitative analysis, a 3D spherical region of interest (ROI) was drawn around the site of the abnormal Ga-68 PSMA uptake, and the ratio of SUVmax of tumor (T) to SUVmax of the contralateral corresponding area (TBR) was calculated. Each patients' PSMA brain PET was fused to the corresponding MRI and reviewed for concordance.

Thirty patients were included in the study, a total of 49 lesions were detected on MRI, and fused PET/MR images showed increased Ga-68 PSMA uptake in all these lesions. Multifocal lesions were better appreciated on fused PET-MR images, and concordance between MRI and PET was 100 % for patient and lesion-wise detection. Recurrent glioma lesions showed SUVmax and SUVmean values (median and IQR) 6.0 (4.4-8.2) and 3.3 (2.8-3.7), respectively. Lesions labeled as radiation necrosis on MRI did not show tracer accumulation.

Ga-68 PSMA has potential utility for evaluating recurrence in HGG and its potential for theranostics would encourage its use in the evaluation of these patients.