PSMA PET/CT in the diagnosis of prostate cancer: why and when?

Prostate-specific membrane antigen (PSMA) is expressed in most primitive and metastatic prostate cancer (PCa), and PSMA inhibitors conjugated with the radionuclides Gallium 68 (68Ga) and fluoride 18 (18F) have been evaluated to detect PCa; moreover, tumour uptake, which represents PSMA expression, is highly correlated with the aggressiveness of the primary prostatic tumour. PSMA positron emission tomography/computed tomography (PET/CT) demonstrated to be sensitive for the detection of primary prostatic lesions, regional lymphadenopathy and clinical metastases in case of biochemical recurrence. In this respect, PSMA PET/CT has been evaluated in men enrolled in clinical trials candidate to initial or repeat prostate biopsy especially in the presence of clinical high risk for PCa, Active Surveillance (AS) and/or in case of negative histology of Prostate Imaging Reporting and Data System (PI-RADS score) 4-5 targeted biopsy. Although many experimental studies reported a superimposable detection rate for PCa of PSMA PET/CT vs. mpMRI targeted biopsy, still today, the use of PSMA PET/CT is experimental and had some limitations: cost, availability, patient characteristics, local expertise and false negative rate. Although prospective and randomized studies are awaited, including a greater number of patients, PSMA PET/CT evaluation could be proposed in the presence of claustrophobia, cardiac pacemaker and severe obesity especially in men at high risk for PCa.