The Maximum Standardized Uptake Value in Patients with Recurrent or Persistent Prostate Cancer after Radical Prostatectomy and PSMA-PET-Guided Salvage Radiotherapy – A Multicenter Retrospective Analysis

Abstract

<h3>Purpose/Objective(s)</h3> Recurrence rate after salvage radiotherapy (sRT) is heterogeneous and additional prognostic markers are needed to improve risk-stratification and guide personalized treatment. We evaluated the association of the maximum standardized uptake value (SUVmax) in positron-emission tomography targeting prostate-specific-membrane-antigen (PSMA-PET) prior to sRT on biochemical recurrence free survival (BRFS) in a large multicenter cohort. <h3>Materials/Methods</h3> Patients who underwent ⁶⁸Ga-PSMA11-PET after radical prostatectomy (RP) due to biochemical recurrence or PSA-persistence were enrolled in four high-volume centers in this retrospective multicenter study. Only patients with PET-positive local recurrence (LR) and/or nodal recurrence (NR) within the pelvis were included. Patients were treated with intensity-modulated-sRT to the prostatic fossa and elective lymphatics in case of nodal disease. Dose escalation was delivered to PET-positive LR and NR. Androgen deprivation therapy was administered at the discretion of the treating physician.LR and NR were manually delineated using and SUVmax was extracted for LR and NR. Cox-regression was performed to analyze the impact of clinical parameters and the SUVmax-derived values on BRFS, defined as serum prostate-specific-antigen >0.2 ng/ml above the post-sRT-nadir without initiation of additional salvage therapies or death of any cause. <h3>Results</h3> 235 patients with a median follow up (FU) of 24 months were included in the final cohort. The presence of LR was associated with favorable BRFS (p=0.016). Presence of NR was associated with unfavorable BRFS (p=0.007). While there was a trend for SUVmax values ≥ median (p=0.071), SUVmax values ≥ 75%quartile in LR were significantly associated with unfavorable BRFS (p=0.022, HR: 2.1, 95%CI 1.1-4.6). SUVmax value in NR was not significantly associated with BRFS. SUVmax in LR stayed significant in multivariate analysis (p=0.030). Sensitivity analysis with patients for who had a FU of >12 months (n=197) confirmed these results. <h3>Conclusion</h3> In patients with biochemical recurrence/persistence after RP, presence of PSMA-expressing pelvic lymph nodes on PET is associated with less favorable BRFS after salvage-radiotherapy. The non-invasive biomarker SUVmax can prognosticate outcome in patients undergoing sRT and recurrence confined to the prostatic fossa in PSMA-PET.