A Pilot Study of 18F-rhPSMA-7.3-PET/MRI to Reduce Mischaracterization of Active Surveillance and Focal Therapy Candidates With Occult Higher Risk Disease.

Abstract

Introduction: PSMA-PET offers an opportunity to reduce the mischaracterization of disease in active surveillance (AS) and focal therapy (FT) candidates. We describe the results of a pilot clinical trial evaluating ¹⁸F-radiohybrid(rh)PSMA-7.3-PET/MRI to detect occult adverse pathology among potential AS and FT candidates (NCT05852041).

Methods: We enrolled 20 men with low risk or favorable intermediate risk prostate cancer and Decipher score ≥ 0.45 diagnosed after an MRI-informed prostate biopsy. All patients underwent PSMA-PET/MRI followed by either PET/MRI-guided biopsy or radical prostatectomy within 90 days. The outcome of interest was detection of grade group (GG) 3-5 disease, seminal vesicle invasion (pT3b), or lymph node involvement (pN1). A detection rate of 15% for this outcome was considered clinically significant. Management decisions and confidence in those decisions were recorded before and after the scan using a 3-point scale. A paired t-test was performed to compare the change in confidence decisions.

Results: At enrollment, 17 patients (85%) had favorable intermediate risk and 3 (15%) had low risk prostate cancer. The median Decipher score was 0.58 (IQR 0.49-0.65). Five patients (25%) demonstrated the outcome of interest based on upgrading alone. None had upstaging to pT3b or pN1. Major changes in management plan occurred in 7 patients (35%). Average confidence in decisions improved from moderate (2.05) to high (2.80) after the scan (p < 0.001).

Conclusions: ¹⁸F-rhPSMA-7.3-PET/MRI can detect occult higher risk disease in men who are otherwise candidates for AS or FT. The scan prompted major changes in management and increased confidence in the final treatment strategy.