Impact of PSMA-PET and conventional imaging on contemporary management in patients with biochemical recurrence after radical prostatectomy.

Abstract

43 Background: Prostate-specific membrane antigen (PSMA) PET imaging is recommended for patients with biochemical recurrence (BCR) after radical prostatectomy (RP). This study describes the early clinical impact of PSMA-PET compared to conventional imaging (CT, MRI, or bone scintigraphy) in a contemporaneous period. Methods: This retrospective study includes patients with BCR after RP (defined as PSA≥0.2 after undetectable PSA post-operatively) who underwent PSMA-PET or conventional imaging (CI) between 2010-2023. The primary outcome was positive detection rate. The secondary outcomes were rates of salvage treatment (XRT±ADT) and second BCR. Cox proportional hazards modeling was used to predict risk of salvage treatment and second BCR. Results: 217 post-RP patients were included. Of the 146 patients who underwent PSMA-PET and the 71 who underwent CI, 77 (52.7%) and 7 (9.9%) patients had positive imaging findings at a median PSA value of 0.23 (IQR 0.21-0.33) and 0.25 (IQR 0.25-0.44), respectively (p=0.36). 48 patients received both imaging modalities; 4 had positive results in both PSMA-PET and CI, while 26 were positive for PSMA-PET only, and 2 were positive on CI only. Patients underwent salvage therapy at lower median PSA values in the PSMA-PET group (0.40 vs 0.51, p<0.01). On unadjusted survival analysis, there were no differences in salvage therapy rates or second BCR rates between PSMA-PET or CI groups. On multivariable Cox proportional hazards modeling, year of PSA recurrence (HR 0.89, 95% CI 0.84-0.95), BMI (HR 1.45, 95% CI 1.02-2.07), ≥GG3 (HR 1.77 95% CI 1.3-2.4), and undetectable PSA≥6 months after RP (HR 0.50 95% CI 0.34-0.72) were associated with salvage treatment, but imaging modality was not. High genomic risk scores (Decipher>0.60) may be associated with second BCR (HR 2.03 95% CI 0.99-4.18, p=0.05) while other variables were not. Conclusions: PSMA-PET usage increased over the period of this study with higher sensitivity at lower median PSA at BCR. Imaging modality did not predict rates of salvage therapy or second BCR, while other clinical risk factors such as adverse pathology and high genomic risk score did. Analysis with a historical cohort is pending.