Clinical outcomes after utilization of PSMA PET scans in patients with biochemical recurrent prostate cancer.

57 Background: The optimal management of biochemical recurrent prostate cancer (BCR) remains unknown. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) scans can visualize micrometastatic disease, thus expanding treatment options for BCR from observation or androgen deprivation therapy (ADT) to potentially include metastasis-directed radiation (XRT) or next-generation hormonal agents (NHA). We aimed to describe how BCR patients were managed after PSMA PET scans and their clinical outcomes. Methods: We performed a retrospective chart review of 262 patients from the University of Michigan’s PSMA PET scan database (825 patients with scans 2017–2021). Patients who received maximal local therapy (defined as XRT alone n=199 or surgery + XRT n=63) are presented. Only patients with BCR and a minimum of 1 year follow-up after scans were included. Baseline patient and tumor characteristics, PSMA PET scan results, first and subsequent therapy delivered after PSMA PET, and prostate-specific antigen (PSA) and standard imaging results post PSMA PET were annotated. Primary endpoint is time from first post-scan therapy (within 6 months of scan) to subsequent therapy. Secondary outcomes include probability of no subsequent therapy in 1 year based on first post-scan therapy and PSMA scan findings and PSMA PET findings and association with Gleason score, PSA at BCR, and time from diagnosis to PSMA scan. Results: Of 262 patients with maximal local therapy, 115 met inclusion criteria. Primary definitive treatment was XRT alone in 58% and surgery + XRT in 42%. Median PSA at time of scan was 4.4 ng/mL, and PSMA PET was positive in 87%. First therapy rendered after PSMA PET included 15% no therapy, 26% XRT only, 28% systemic therapy only (ADT +/- NHA), 27% combination therapy (XRT +/- systemic), and 4% other. Subsequent therapy was given in 26%. The median time from first to subsequent therapy was 41 months in patients who received XRT alone as first therapy and not reached for those with combination XRT + ADT. None of the 33 treated with combination therapy required subsequent therapy in 1 year. Remainder of analyses incomplete due to small sample sizes. Results to be updated by time of symposium. Conclusions: This observational study characterizes longer term clinical outcomes in patients with BCR who undergo various therapies after PSMA PET scans. Data may inform current decision making while prospective clinical trial data is awaited.