Ga-68 Prostate Specific Membrane Antigen PET/CT in Gliomas

Overview

As a part of molecular imaging, many PET tracers have been investigated in this regard. Those include 18F-FDG being glucose analogue, 18F-FLT representing nucleoside metabolism, and 18F-FDOPA, 18F-FET, 11C-MET as amino acids analogues. Among these, 18F-FDG is the most commonly used tracer due to its broader use and easy availability. However, high physiological uptake in the brain is a significant limitation. The main limitation of other tracers is the need for onsite cyclotrons for their production, making their availability difficult. So, the search for an ideal modality is still ongoing, and the latest addition to this search is a radio ligand labeled Prostate Specific Membrane Antigen (PSMA). It is a new but potentially promising radiotracer, currently showing its utility in different malignancies. Investigators, therefore, aim to identify whether Ga-68 PSMA PET-CT has better diagnostic accuracy in the detection of recurrent gliomas than conventional imaging modalities.

Prostate Specific Membrane Antigen (PSMA is a type II membrane glycoprotein and is typically overexpressed in primary and metastatic lesions of prostate malignancy as the name suggests. However, this overexpression is not limited to prostate cancer only. It has been reported that, PSMA is overtly expressed in the vascular endothelium of various other malignancies where significant neovascularization is seen. Gliomas being highly vascularized tumors, have shown significant PSMA expression in their vascular endothelium especially in high grade ones. If this PSMA expression can be assessed through noninvasive molecular imaging, this would further ease the management these tumors. Different lesions have shown different grades of PSMA uptake in the PET/CT with high grade gliomas showing high uptake. Most of the articles published till date are either case reports or studies comprising very few numbers of patients. We would like to use the PET tracer Ga -68 PSMA for the detection of recurrence in patients with glioma. Investigators believe that 68 Ga PSMA PET-CT has the potential to play an imperative role in noninvasively evaluating recurrent gliomas and can overcome the limitations of the currently used modalities. Besides, extrapolation of the PSMA expression, which is indirect evidence of neovascularization, can also be used to assess treatment options like VEGF inhibitors (Bevacizumab). These studies can also pave the way for further studies involving PSMA-based radio ligand therapy, which is currently being successfully applied in patients with metastatic prostate cancer.