Intra-Individual Comparisons of [18F]fluorodeoxyglucose and Prostate-Specific Membrane Antigen Positron Emission Tomography in Prostate Cancer Patients Across Different Disease States: New Insights into Disease Heterogeneity

Background/Objectives: Prostate-specific membrane antigen (PSMA) PET/CT is more accurate than CT and bone scans for staging intermediate and high-risk prostate cancer (PCa). Fluorodeoxyglucose (FDG) PET has improved disease characterisation in metastatic castrate-resistant PCa (mCRPCa) and indicates patients with a particularly poor prognosis. The aim of this study was to assess the benefits of both PSMA and FDG PET in PCa staging by the direct intra-individual comparison of PSMA and FDG uptake patterns. Methods: Patients who underwent both PSMA and FDG PET/CT from 2015 to 2020 at our institution were identified and included if they had a histological or clinical diagnosis of PCa. Medical records were reviewed for demographic information and clinical details (including PSA, previous treatment, and disease status). Imaging interpretation was based on reporting by experienced nuclear medicine physicians. Results: Sixteen patients were identified. In 11 men with localised or hormone-sensitive PCa, PSMA-avid and FDG-avid disease was seen in 64% (n = 7) and 9% (n = 1) of patients, respectively. FDG-avid disease was present in 60% of patients with mCRPCa (n = 3/5), all of whom showed PSMA uptake. Of note, one patient showed higher initial FDG uptake that progressed in size and uptake on PSMA PET over 12 months. Conclusions: FDG PET might be useful in the assessment of patients with high clinical suspicion of metastases (e.g., high PSA, symptoms) with negative PSMA PET, particularly in castrate-resistant PCa.