EAU Biochemical Recurrence Risk Classification and PSA Kinetics Have No Value for Patient Selection in PSMA-Radioguided Surgery (PSMA-RGS) for Oligorecurrent Prostate Cancer

SIMPLE SUMMARY: In prostate cancer patients with low-volume/oligo-metastatic relapse after radical prostatectomy, radioguided surgery against prostate-specific membrane antigen (PSMA-RGS) might be an option. However, patient selection remains difficult. In this study, we analyzed if the EAU risk stratification for biochemical recurrence (BCR) and the PSA development over time predict the oncological success of PSMA-RGS. We found that neither EAU BCR risk groups nor PSA doubling time and velocity are significant predictors for a complete biochemical response or prolonged biochemical recurrence- or subsequent therapy-free survival. Therefore, PSMA-RGS may be offered to suitable patients independently of prior PSA development and EAU BCR risk group after radical prostatectomy. ABSTRACT: Objective: To assess the influence of biochemical recurrence (BCR) risk groups and PSA kinetics on the outcomes of radioguided surgery against prostate-specific membrane antigen (PSMA-RGS). Currently, neither BCR risk group nor PSA doubling time (PSA-DT), or PSA velocity (PSA-V) are actively assigned or relevant for counseling prior to PSMA-RGS. Methods: We retrospectively analyzed PSMA-RGS cases for oligorecurrent prostate cancer between 2014 and 2023. BCR risk groups, PSA-DT, and PSA-V were analyzed as predictors for complete biochemical response (cBR, PSA < 0.2 ng/mL), BCR-free, and therapy-free survival (BCRFS, TFS). Results: Of 374 included patients, only 21/374 (6%) and 201/374 (54%) were classified as low- and high-risk BCR (no group assignment possible in 152/374, 41%). A total of 13/21 (62%) patients with low- and 120/201 (60%) with high-risk BCR achieved cBR (p = 1.0). BCR classification was no predictor for BCRFS (HR:1.61, CI: 0.70–3.71, p = 0.3) or subsequent TFS (HR:1.07, CI: 0.46–2.47, p = 0.9). A total of 47/76 (62%) patients with PSA-DT ≤ 6 mo and 50/84 (60%) with PSA-DT > 6 mo achieved cBR (p = 0.4). PSA-DT was not associated with cBR (OR: 0.99, CI: 0.95–1.03, p = 0.5), BCRFS (HR: 1.00, CI: 0.97–1.03, p = 0.9), or TFS (HR: 1.02, CI: 0.99–1.04, p = 0.2). Consistent negative findings were recorded for PSA-V. Conclusions: The BCR risk groups and PSA kinetics do not predict the oncological success of PSMA-RGS performed at low absolute PSA values. Indolent low-risk BCR is rarely treated by PSMA-RGS.