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

Purpose: [F]fluorodeoxyglucose ([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 [F]FDG PET/CT. This study aimed to evaluate [F]PSMA-1007 and [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 [F]PSMA-1007 and [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 [F]PSMA-1007 PET/CT, whereas only 15 were detected on [F]FDG PET/CT (62.3% vs. 37.7%, p < 0.0001). A high SUV for [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 [F]FDG uptake were mostly ductal dominant (acinar-dominant 4/27; ductal-dominant; 11/15, p < 0.001), with lower [F]PSMA-1007 uptake than tumours without [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 [F]FDG positive. Biochemical failure was observed in 14.8% (4/27) of patients with [F]FDG negative tumours but in 53.3% (8/15) of patients with [F]FDG positive tumours (p = 0.013).

Conclusions: [F]PSMA-1007 PET/CT was superior to [F]FDG PET/CT in detecting primary PCa. In contrast, tumours with [F]FDG uptake are associated with larger size, a ductal-dominant type, and likely to undergo metastasis at staging and biochemical failure postoperatively.