Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
3288 - Clinicopathologic Predictors of PSMA-PET Detection, Recurrence Pattern, and Biochemical Outcome Following Salvage Radiotherapy after Radical Prostatectomy
Presenter(s)
Ramotallah Jubril, MS - Purdue University, West Lafayette, IN
R. D. Jubril1, A. V. Prabhu2, O. Ishaq Jr2, J. A. Ocana3, M. Tann3, C. F. Njeh2, C. Bahler4, J. A. Holmes2, and O. M. Oderinde1,2; 1Advanced Molecular Imaging in Radiotherapy (AdMIRe) Research Laboratory, School of Health Sciences, Purdue University, West Lafayette, IN, 2Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN, 3Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN, 4Department of Urology, Indiana University School of Medicine, Indianapolis, IN
Purpose/Objective(s):
Biochemical recurrence (BCR) after radical prostatectomy (RP) presents heterogeneous recurrence patterns and variable outcomes following salvage radiotherapy (sRT). We hypothesized that clinicopathologic features and PSA burden at recurrence are associated with PSMA-PET detection, recurrence localization, and biochemical disease-free survival (bDFS) following sRT.Materials/Methods:
A retrospective single-institution study included 140 patients with BCR after RP who underwent 68Ga-PSMA-PET/CT prior to sRT ± androgen deprivation therapy. Collected variables included age, PSA at recurrence, ISUP grade, pT-stage, pN-stage, extraprostatic extension (EPE), surgical margins, seminal vesicle invasion (SVI), and time to BCR (tBCR). PSMA-PET-positive cases were stratified by recurrence sites as prostate bed only (PBO) versus pelvic nodal involvement with or without prostate bed (PLNI). Receiver operating characteristic (ROC) analysis assessed PSA discrimination for imaging detection. Logistic regression identified predictors of imaging positivity and recurrence localization, while Kaplan-Meier and Cox proportional hazards models evaluated bDFS following sRT.Results:
PSMA-PET detected recurrence in 77/140 (55%) patients. Higher PSA (median 0.83 vs. 0.39 ng/mL, p<0.001), advanced pT-stage (p=0.035), EPE (p=0.047), and older age (p=0.03) were associated with PSMA-PET positivity. On multivariable analysis, PSA (OR=2.07; p=0.003) and age (OR=1.07; p=0.016) were the sole independent predictors. ROC analysis yielded AUC=0.74 with an optimal threshold of 0.58 ng/mL (68% sensitivity and 75% specificity). Among PSMA-positive patients, 36% had PBO and 64% had PLNI. PBO recurrence patterns are associated with longer tBCR (37.5 vs. 15 months; p=0.006). SVI and advanced pT-stage predicted PLNI on univariable analysis but were not independently predictive. Among 133 evaluable patients (median follow-up 31 months), secondary biochemical failure occurred in 30.1%. Estimated bDFS at 24, 36, and 60 months were 90%, 80%, and 54%, respectively. Univariable Cox regression demonstrated increased hazard of failure with SVI (HR=2.39; p=0.031), EPE (HR=2.82; p=0.012), and advanced pT-stage (HR=1.64; p=0.021), though none demonstrated independent significance.Conclusion:
PSA burden at recurrence was the primary determinant of PSMA-PET detection, with age showing a modest independent association. Recurrence patterns reflected disease behavior, as PBO was associated with longer tBCR. Although adverse pathologic features were associated with pelvic nodal disease and reduced biochemical control after sRT, none remained independently predictive. This highlights the biological heterogeneity of recurrent prostate cancer, supporting continued refinement of risk-adapted salvage strategies.