Oligometastatic disease in biochemical recurrence of prostate cancer: Prevalence on PSMA PET/CT and consecutive metastasis-directed therapy - Experience at a tertiary referral center.

AIM The aim of our study was to address the prevalence of oligometastatic recurrent prostate cancer (PCa) on PSMA-PET and the associated practice of metastasis-directed therapy (MDT). Next, we aimed to determine a PSA threshold below which most patients had local and/or oligometastatic recurrence on PSMA-PET. METHODS One hundred and ten consecutive patients with biochemical recurrence (BCR) after radical prostatectomy (RP) ± radiation were referred for 68Ga-PSMA-11 or 18F-DCFPyL PET/CT. We correlated the location and number of PSMA-positive lesions against the treatment choice after imaging. Detection rates were stratified by PSA levels at the time of PET/CT. The study design was monocentric retrospective. RESULTS Thirty-four patients (30.9%) had a PSMA-negative scan, while 17 (15.5%) had local recurrence and 59 (53.6%) had metastatic recurrence on PSMA-PET. ROC analysis revealed a cut-off of ≤3 metastatic lesions on PSMA-PET for the steering of treatment decisions towards MDT rather than solely systemic therapy (AUC: 0.88). Defined as 3 or fewer metastatic lesions, oligometastatic recurrent PCa was found in up to 30% (33/110) of all patients. At PSA levels below 3.5 ng/ml, the rate of PSMA-positive disease that was locally confined or oligometastatic was 76% (45/59), dropping significantly to 29.4% (5/17) above this threshold (p<0.001) as polymetastatic findings became more frequent. CONCLUSION The detection of ≤3 oligometastases on PSMA-PET encouraged the consecutive pursuit of MDT instead of systemic therapy alone. PSMA-PET predominantly captured patients at recurrence stages amenable to localized treatment when initiated at PSA levels below 3.5 ng/ml.