High AST and the presence of liver metastases may guide for the need for FDG PET in advanced prostate cancer patients

Abstract Objective 2-[18F]fluoro-D-glucose (FDG) Positron Emission Tomograpy/Computed Tomography (PET/CT) may help to evaluate the tumor heterogeneity in patients with metastatic castration-resistant prostate cancer (mCRPC) and determine treatment eligibility for Prostate Specific Membrane Antigen (PSMA) targeted radioligand therapy (PSMA-RLT). The aim of the study is to evaluate the biochemical and clinical parameters which can predict the presence of FDG-PSMA discordant disease. Material and Methods A total of 70 advanced mCRPC patients who underwent [68Ga]Ga-PSMA-11 PET and FDG PET/CT between August 2016 and June 2021 were retrospectively analyzed. Inter-tumoral heterogeneity was both visually and semi-quantitatively evaluated. Baseline clinical, laboratory and PSMA PET/CT related semi-quantitative parameters were analyzed to predict FDG discordant disease with logistic regression analysis. A receiver operating characteristic (ROC) analysis was performed to determine the threshold values for the statistically significant parameters. Results 29/70 (41.4%) of the patients had FDG-PSMA discordant disease based on visual assessment. Overall 427 mismatch lesions (FDG > PSMA) were detected: the majority of these lesions were in the bones (n = 236, 55.2%), lymph nodes (n = 95, 22.2%), and visceral organs (n = 88, 20.6%). Most significant parameters to predict FDG-PSMA discordant disease were serum AST (Youden Index derived cut-off value ≥ 24.5 IU/l, sensitivity 75.8%, specificity 73.2%, AUC = 0.79) and the presence of liver metastases. Conclusion The presence of liver metastases, elevated AST may be easily used in clinical practice to predict FDG-PSMA discordant disease.