Purpose of the report: Using morphological and functional imaging to discriminate recurrence from postradiation-related modifications in patients with glioblastomas remains challenging. This pilot study aimed to assess the feasibility of using 68 Ga-prostate-specific membrane antigen (PSMA) 11 PET/CT compared with 18 F-FDOPA PET/CT to detect early recurrence.
Methods: Nine patients followed up for glioblastomas who received MRI during 12 months of follow-up were referred for both 68 Ga-PSMA-11 and 18 F-FDOPA PET/CT. The SUV max , lesion-to-striatum ratio, lesion-to-normal parenchyma ratio, and lesion-to-salivary gland ratio were calculated.
Results: Good correlation between 18 F-FDOPA and 68 Ga-PSMA PET/CT findings was seen in 5 patients. In 4 patients, the findings of both examinations were consistent with recurrence but were better visualized with the PSMA PET/CT. Examinations of the fifth patient were suggestive of postradiation-related changes and were better analyzed with the PSMA PET/CT, which displayed relatively low uptake compared with DOPA PET/CT. Conversely, 4 patients showed conflicting results: recurrence was not detected on the PSMA PET/CT because of previously introduced bevacizumab treatment; in another patient, both examinations were consistent with recurrence, but there was an uptake mismatch at the suspected lesion sites, and 2 patients presented with inconsistent findings.
Conclusions: Despite a few discrepancies, this study highlights the potential role of 68 Ga-PSMA-11 PET/CT for discriminating postradiation inflammation from recurrence. 68 Ga-PSMA-11 PET/CT has an excellent lesion-to-background ratio, and false-positive and false-negative results could be minimized through implementing certain protocols before performing the examination. More powerful prospective studies are required to validate our results.
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