Association of prostate-specific antigen kinetics with gallium-68 prostate-specific membrane antigen PET/computed tomography positivity in biochemical recurrence after radical prostatectomy.

Abstract

Biochemical recurrence (BCR) after radical prostatectomy occurs in 20-40% of patients. Prostate-specific membrane antigen (PSMA) PET/computed tomography (CT) is the preferred imaging modality for recurrence, but detection rates decline at low prostate-specific antigen (PSA) levels. The role of PSA kinetics in postradical prostatectomy BCR remains unclear. We evaluated the association between PSA kinetics and PSMA PET/CT positivity in postradical prostatectomy BCR. We retrospectively analyzed postradical prostatectomy patients (2013-2024) who developed BCR and underwent 68Ga-PSMA PET/CT. Patients with prior therapy, PSA persistence, inadequate follow-up, or non-PSMA imaging were excluded. Clinicopathological and PSA kinetic variables were compared between groups. Logistic regression assessed associations with PET positivity, and receiver operating characteristic (ROC) analysis identified exploratory cut-offs. Of 973 men who underwent radical prostatectomy, 64 met the inclusion criteria. Nineteen (29.7%) had positive and 45 (70.3%) had negative scans. Baseline characteristics were comparable. Median PSA at imaging was 0.30 ng/ml. PET-positive patients had higher PSA velocity (PSAV) (0.58 vs. 0.27 ng/ml/year; P = 0.020) and shorter PSA doubling time (PSADT) (3.23 vs. 5.80 months; P = 0.009). On univariable analysis, PSAV [odds ratio (OR): 3.31, P = 0.027), PSADT (OR: 0.86, P = 0.050), and PSA at imaging (OR: 10.68, P = 0.032) were associated with PET positivity. ROC analysis showed moderate discrimination for PSADT (AUC: 0.71) and PSAV (AUC: 0.69). Shorter PSADT and higher PSAV predicted PSMA PET positivity in men with BCR after radical prostatectomy. Exploratory cut-offs of PSADT less than 3.9 months and PSAV more than 0.54 ng/ml/year were identified but require external validation.