Combination of [ 18 F]FDG and [ 18 F]PSMA-1007 PET/CT predicts tumour aggressiveness at staging and biochemical failure postoperatively in patients with prostate cancer

Purpose [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) positron emission tomography/computed tomography (PET/CT) has limitations in prostate cancer (PCa) detection owing to low glycolysis in the primary tumour. Recently, prostate-specific membrane antigen (PSMA) PET/CT has been useful for biochemical failure detection and radioligand therapy (RLT) guidance. However, few studies have evaluated its use in primary prostate tumours using PSMA and [ 18 F]FDG PET/CT. This study aimed to evaluate [ 18 F]PSMA-1007 and [ 18 F]FDG PET/CT for primary tumour detection and understand the association of metabolic heterogeneity with clinicopathological characteristics at staging and postoperatively. Method This prospective study included 42 index tumours (27 acinar and 15 ductal-dominant) in 42 patients who underwent [ 18 F]PSMA-1007 and [ 18 F]FDG PET/CT and subsequent radical prostatectomy. All patients were followed for a median of 26 mo, and serum prostate-specific antigen levels were measured every 3 mo to evaluate biochemical failure. One-way analysis of variance, Tukey’s multiple comparison test, and Fisher’s exact test were performed. Results All 42 index tumours were detected on [ 18 F]PSMA-1007 PET/CT, whereas only 15 were detected on [ 18 F]FDG PET/CT (62.3% vs. 37.7%, p < 0.0001). A high SUV max for [ 18 F]PSMA-1007 was observed in tumours with high Gleason scores (GS 6–7 vs. GS 8–10; 12.1 vs. 20.1, p < 0.05). Tumours with [ 18 F]FDG uptake were mostly ductal dominant (acinar-dominant 4/27; ductal-dominant; 11/15, p < 0.001), with lower [ 18 F]PSMA-1007 uptake than tumours without [ 18 F]FDG uptake (SUVmax 16.58 vs. 11.19, p < 0.001). There were 16.6% (7/42) of patients with pStage IV in whom the primary tumours were [ 18 F]FDG positive. Biochemical failure was observed in 14.8% (4/27) of patients with [ 18 F]FDG negative tumours but in 53.3% (8/15) of patients with [ 18 F]FDG positive tumours ( p = 0.013). Conclusions [ 18 F]PSMA-1007 PET/CT was superior to [ 18 F]FDG PET/CT in detecting primary PCa. In contrast, tumours with [ 18 F]FDG uptake are associated with larger size, a ductal-dominant type, and likely to undergo metastasis at staging and biochemical failure postoperatively.