18F-PSMA PET/CT for Visualization of Glioblastoma Multiforme

This is a pilot study to determine uptake of PET tracer 18F-PSMA-1007 in primary glioblastoma.

Glioblastoma multiforme (GBM) is a highly vascularised tumour. Previous studies have shown that prostate-specific membrane antigen (PSMA) is robustly expressed by the tumour vascular endothelium of GBM and thus could be an interesting target for diagnosis and treatment. Several groups have focused on the development of 18F-labeled PSMA ligands for PET imaging. 18F as a radionuclide has several advantages over 68Ga. Due to the longer half-life compared (110 min for 18F compared to 68 min for 68Ga) allows for centralized production and distribution to greater areas. Furthermore, multiple doses of 18F can be produced in one synthesis, while each gallium generator provides only one or two elutions per day. Moreover, due to the decreased positron energy (0.65 MeV for 18F compared to 1.90 MeV for 68Ga) imaging resolution may be higher. The first generation of 18F-PSMA ligands, such as 18F-DCFBC, suffered from high background due to slow blood clearance. The second generation 18F-DCFPyL PSMA ligand has a fast elimination via the urinary route and showed high tumor-to-blood ratios. Benesova et al developed the 177Lu-DKFZ-61, which is suitable for labelling with both diagnostic 68Ga as well as therapeutic 177Lu (beta-emitting) or 225Ac (alpha-emitting), and Giesel at al developed 18F-PSMA-1007, which is structurally related to DKZF-617. Since various studies have shown feasibility of PSMA imaging in brain lesions of patients with recurrent GBM, we want to extend these results in a cohort of patients with a first-diagnosed suspected GBM. We want to use the PET tracer 18F-PSMA-1007. If this technique can be implemented successfully, the added value of 18F-PSMA PET/CT for tumour grading and differential diagnosis could be investigated further in larger patient cohorts (especially with recurrent brain lesions). These studies will pave the way for further studies involving 177Lu-PSMA-based therapy, which is currently applied in patients with metastatic prostate cancer.