Lymph node staging with fluorine-18 prostate specific membrane antigen 1007-positron emission tomography/computed tomography in newly diagnosed intermediate- to high-risk prostate cancer using histopathological evaluation of extended pelvic node dissection as reference.

Abstract

Fluorine-18 (¹⁸F) prostate-specific membrane antigen (PSMA) 1007 (¹⁸F-PSMA-1007) is a radiotracer used in prostate cancer (PCa) staging. So far, no large histopathological validation study has been conducted. The objective was to determine diagnostic accuracy of ¹⁸F-PSMA-1007 PET/CT compared to histopathological results of extended pelvic lymph node dissection (ePLND) in men with intermediate- or high-risk PCa. Men with newly confirmed intermediate- or high-risk PCa were prospectively enrolled in the Molecular Imaging ¹⁸F-PSMA-1007 PET/CT for lymph Node sTaging in primary PCa (MINT) trial. PET/CT images were read by two nuclear medicine physicians. Diagnostic accuracy was evaluated by histopathology of template resections. Sensitivity, specificity, and positive and negative predictive values (PPV, NPV) for LNI detection of ¹⁸F-PSMA-1007 PET/CT were calculated. Ninety-nine men were evaluated; 30.3% showed histologically confirmed LNI. Median number of resected nodes was 22 (IQR 17-28). Patient-based sensitivity, specificity, PPV, and NPV were 53.3% (95% CI 34.3-71.7%), 89.9% (95% CI 80.2-95.8%), 69.6% (95% CI 51.2-83.3%), and 81.6% (95% CI 75.0-86.8%), respectively. Template-based sensitivity was 12.9% (95% CI 5.7-23.9%), specificity 97.7% (95% CI 96.6-98.5%), PPV 23.5% (95% CI 12.7-39.5%), and NPV 95.3% (95% CI 94.9-95.7%). ¹⁸F-PSMA-1007 PET/CT showed high specificity but moderate to low sensitivity for LNI detection in intermediate- and high-risk PCa. It cannot replace ePLND for staging. Additional studies are needed to determine exact scan indications in lymph node staging for the primary diagnostic pathway in intermediate- or high-risk PCa. December 12, 2018, Netherlands Trial Registry, NTR7670 ( https://www.trialregister.nl/trial/7428 ).