PSMA PET/CT Accuracy in Diagnosing Prostate Cancer Nodes Metastases

This study aimed to evaluate the diagnostic accuracy of prostate-specific membrane antigen (PSMA)-directed positron emission tomography/computed tomography (PET/CT) in pelvic nodal staging, using postoperative histopathology data as the reference standard.

From January 2020 to June 2024, 78 patients with clinically significant prostate cancer (PCa) (ISUP Grade Group 2) underwent radical prostatectomy plus extended pelvic lymph node dissection (ePLND): 60 (77%) vs. 18 (23%) men had an intermediate vs. high risk PCa. All the patients underwent PSMA PET/TC before surgery for clinical staging and nodes focal uptake (standardized uptake value "SUVmax) was evaluated to rule out the presence of metastases.

PSMA PET/CT was suspicious for nodes metastases in 16/78 (20.5%) men (median SUVmax 26.2), conversely, histology demonstrated nodes metastases in 18/78 (23.1%). PSMA PET/CT was negative for nodal involvement in all Grade Group 2 (GG2) PCa, positive in 4/4 (100%) GG3 PCa, and in 10/14 (71.4%) GG5 PCa. In detail, PSMA PET/CT was false negative in 2/4 PCa, characterized by GG5 plus ductal adenocarcinoma. Overall, PSMA PET/CT sensitivity, specificity, positive and negative predictive value, and diagnostic accuracy in diagnosing nodal metastases were equal to 87.5, 96.8, 87.5 96.7, and 92.3%, respectively.

PSMA PET/CT demonstrated an overall diagnostic accuracy of 92.3% in nodal staging (100% in GG2 PCa), which decreased to 63.6% in GG5 PCa. In high-risk patients or in case of ductal adenocarcinoma, a negative PSMA PET/CT does not rule out the need for ePLND.