The Role of 18F-PSMA-1007 PET-CT Imaging In Treatment Management Of Malignant Brain Tumors: Pilot Study From Azerbaijan

Introduction: Prostate-specific membrane antigen-PSMA (also known as glutamate carboxypeptidase II) is overexpressed in prostate cancer epithelium, making it a target for molecular imaging and therapy. In addition, PSMA was also found to be expressed in the endothelium of tumor-associated neovasculature in some solid malignancies (breast, lung and urothelial cancer).

We have used [18F]PSMA-1007 to examine the PET/CT scan for the diagnosis primary and metastatic of brain tumors, detection of recurrences after radiotherapy, also to determine the feasibility and utility of [18F]PSMA-1007 PET/CT in treatment management of brain tumors.

Methods: Eight patients were analyzed for brain tumors with brain PET/CT 18F-PSMA-1007 and MRI. Diagnosis of tumor was confirmed histologically by surgical resection/stereotactic biopsy when possible or imaging at follow up. Static PET/CT acquisitions were at one and two hours after injection of 18F-PSMA-1007.

Quantitative PET parameters (SUVmax, tumor/normal brain ratio (T/N), tumor/choroid plexus (T/CP), tumor/sagittal sinus (T/S)) and MRI features (maximal diameters, tumor enhancement) were recorded.

The seven patients have different grades of astrocytoma, including six grade IV (glioblastoma multiforme) and one grade II. One of the patients had multiple melanoma metastases to the brain, which mimicked the brain tumor.

Results: Tumor lesional size varied between 1 cm and 3 cm. There was enhancement in MRI in two of four patients, that 18F-PSMA-1007 PET/CT showed no pathologic accumulation. In rest 18F-PSMA-1007 positive four patients there was concordance on both imaging modalities. In one patient with melanoma metastasis the lesions showed mild 18F-PSMA-1007 uptake. The SUVmax values of lesions in the second hour exam was higher than the first hour exam (p=0.024). While the reference SUV values taken from background brain parenchyma remained unchanged (p=0.351), the choroid plexus and sagittal sinus blood pool measurements were decreased (p=0.035 and p=0.008). Consequently, the highest values of tumor/choroid plexus (T/CP) and tumor/sagittal sinus (T/S) were seen in second hour images (p=0.036 and p=0.022)

Conclusions: 18F-PSMA-1007 PET/CT is a popular diagnostic method in diagnosis and treatment management of prostate cancer patients. Brain tumors showed high tumor-to-background 18F-PSMA-1007 uptake. Thus, 18F-PSMA-1007 is an alternative imaging method for primary and metastatic brain tumors with better image quality. Moreover, in the near future, 18F-PSMA-1007 could indicate a potential for targeted treatment by PSMA based radionuclide with beta/alpha emitters in the theranostic approach to refractory to the main conventional treatment, inoperable primary and metastatic brain tumors.