Early Results from the CONFIRM Trial: Utility of Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography in Active Surveillance for Prostate Cancer.

Abstract

Background and objective: There is growing evidence on the utility of prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) for detection of clinically significant prostate cancer (csPC), but there are limited data on its use in active surveillance (AS). The CONFIRM trial aims to determine the utility of PSMA PET/CT in detecting csPC before confirmatory biopsy during AS.

Methods: This is an initial analysis of a prospective, nonrandomised, crossover clinical trial (ANZCTR ID ACTRN12621001648819) that included men on AS for newly diagnosed low-grade prostate cancer (PC) with "high-risk" features. High risk was defined as grade group (GG) 1 disease with elevated prostate-specific antigen (PSA; >10 ng/ml, or PSA density >0.15 ng/ml/ml), high-volume GG 1, GG 1 with Prostate Imaging-Reporting and Data System 4 or 5 lesion on magnetic resonance imaging (MRI), or low-volume GG 2 PC. Patients underwent multiparametric MRI and [¹⁸F]-labelled radioligand PSMA PET/CT 3-6 mo after diagnosis, and confirmatory biopsy 6-9 mo after diagnosis.

Key findings and limitations: Between November 2021 and September 2023, 60 patients (median age 62.5 yr) were enrolled. PSMA-avid lesions were identified in 44 patients (73.3%), of whom 27 (61.4%) harboured csPC (GG ≥2). Of the PSMA-avid lesions, 20 (45.5%) were MRI-occult. At a subsequent multidisciplinary meeting, active treatment was recommended for 24 patients (40%), with PSMA PET/CT findings influencing 12 (20%) of the decisions. PSMA PET/CT provided reassurance regarding the decision to continue AS by excluding PSMA-avid lesions in 14 cases (38.9%) and multifocal disease in four (11.1%). Our findings are limited by the small sample size and short follow-up.

Conclusions and clinical implications: PSMA PET/CT appears to hold promise for improving risk stratification during AS by identifying csPC and MRI-occult lesions.