Clinical Factors Associated with Suspicious 18F-DCFPyL PSMA PET Activity in Patients Initially Managed with Radical Prostatectomy including PSA <0.5 ng/mL.

PURPOSE There is limited data on PSMA PET/CT for work-up of recurrence after radical prostatectomy (RP) at low PSA values. We evaluated a PSMA PET/CT cohort of post-RP patients, 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 eleven-hospital system from 7/2021-2/2023. 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 one suspicious PSMA-avid lesion. Rates of scan positivity among patients with PSA <0.2 and 0.2-0.5 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 post-operative radiation was associated with suspicious PSMA activity. In the overall cohort, age, PSA at PSMA PET/CT, and RP Gleason Grade (GG) were associated with PSMA positivity. PSADT, EAU risk, and CAPRA-S 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 post-operative 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.