Diagnostic Accuracy of Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography for Primary Lymph Node Staging Before Radical Prostatectomy.

Background and objective: Prostate-specific-membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) is more accurate than conventional imaging for lymph node (LN) staging in prostate cancer. However, it has limitations in detecting micrometastatic lymph node invasion (LNI). Our aim was to evaluate the accuracy of PSMA PET/CT for overall and size-dependent LNI detection in contemporary patients undergoing radical prostatectomy (RP) and pelvic lymph node dissection (PLND).

Methods: Within a high-volume center database, we identified 873 patients who underwent PSMA PET/CT for primary staging before RP and PLND between 2016 and 2021. Data for lymph node status on imaging and histology results were analyzed.

Key findings and limitations: Of 873 patients, 25% (n = 220) had LNI. Median prostate-specific antigen was 8.3 ng/ml (interquartile range 4.3-14.3). The majority of patients had high-risk (53%) or intermediate-risk disease (45%). In the overall cohort, the per-patient sensitivity, specificity, positive predictive value, negative predictive value (NPV), and accuracy calculated for LNI detection via PSMA PET/CT were 45.5%, 92.6%, 67.6%, 83.4%, and 80.8%, respectively. The median metastatic LN size in the group of 120 patients with false-negative PET/CT results was 2.5 mm. For metastatic LNs ≥5 mm, the sensitivity and NPV increased to 68.8% (+23.3%) and 95.4% (+12.0%), respectively. The main limitation is the lack of central review of PSMA PET/CT scans.

Conclusions and clinical implications: PSMA PET/CT is accurate in the staging of pelvic LNs before RP, especially for detection of metastases in LNs with a diameter ≥5 mm.