Clinical Factors Associated with Suspicious ¹⁸F-DCFPyL Prostate-Specific Membrane Antigen Positron Emission Tomography Activity in Patients Initially Managed with Radical Prostatectomy Including Prostate-Specific Antigen < 0.5 ng/mL

Purpose:There are limited data on prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/CT for workup of recurrence after radical prostatectomy (RP) at low PSA values. We evaluated a PSMA PET/CT cohort of patients post RP, focusing on patients with PSA < 0.5 ng/mL.Materials and Methods:We identified a retrospective cohort who underwent piflufolastat F-18 PSMA PET/CT across an 11-hospital system from July 2021 to February 2023. PSMA positivity was determined by radiology reports. Univariable and multivariable logistic regression identified factors associated with suspicious PSMA activity.Results:Median PSA was 0.37 ng/mL (IQR, 0.15-1.29 ng/mL), with 49% of patients overall having at least 1 suspicious PSMA-avid lesion. Rates of scan positivity among patients with PSA < 0.2 and 0.2 to 0.5 ng/mL were 34% and 38%, respectively. Among all patients, 25% (104/415) had pelvic disease (prostate bed or N1) and 24% (100/415) had M1 disease. Among patients with PSA < 0.5 ng/mL, prior postoperative radiation was associated with suspicious PSMA activity. In the overall cohort, age, PSA at PSMA PET/CT, and RP Gleason grade were associated with PSMA positivity. PSA doubling time, European Association of Urology risk, and Cancer of the Prostate Risk Assessment Postsurgical were all associated with suspicious PSMA activity.Conclusions:Over one-third of patients with PSAs < 0.2 ng/mL had imaging findings concerning for recurrence. Prior postoperative radiation was associated with higher rates of PSMA positivity among patients with PSA < 0.5 ng/mL, and half of patients with evidence of PSMA-avid distant metastatic disease underwent metastasis-directed therapy. PET-PSMA imaging at low PSAs can be considered to inform salvage therapies.