68Ga-Prostate-Specific Membrane Antigen-11 PET/CT: A New Imaging Option for Recurrent Glioblastoma Multiforme?

Glioblastoma multiforme (GBM) is the most common and most aggressive primary tumor of the brain. After initial therapy and total resection of GBM, 80% to 90% of recurrences occur at the surgical margins. Currently, limited data are available in the literature on the possible use of Ga-prostate-specific membrane antigen (PSMA-11) for diagnosis of recurrence in GBM patients. The aim was to assess the feasibility and potential of Ga-PSMA-11 PET/CT as a diagnostic procedure in patients with histologically confirmed of GBM and suspected recurrent disease on MRI.

No radiopharmaceutical-related adverse events were noted. Characterization of recurrent disease with MRI included T2-weighted fast spin-echo images, fluid-attenuated inversion recovery and diffusion-weighted imaging sequences, and gadolinium enhanced T1-weighted images. Visual interpretation of PET showed increased accumulation of Ga-PSMA-11 in recurrent lesion detected by T1 contrast enhanced and diffusion-weighted imaging images in all patients with a median SUVmax of the tumor of 6.5 and an SUVmean of 3.5. The median tumor-to-background brain ratio and tumor-to-liver ratio obtained from Ga-PSMA-11 PET/CT were 96.7 and 0.8, respectively.

The extremely low background uptake in normal brain tissue and consequently high tumor-to-brain ratio make Ga-PSMA-11 PET/CT highly promising for diagnosis of recurrent disease in GBM patients. Although PSMA expression in recurrent GBM also opens a potential way for targeted peptide therapy with α/β-emitters as well as for prediction of treatment with antiangiogenic agents, the low tumor-to-liver ratio observed in the majority of patients in this study suggests a limited role of radiolabeled PSMA ligands for targeted radionuclide therapy of recurrent GBM.