Diagnostic accuracy of 18F-PSMA-1007-PET/CT imaging for lymph node staging of prostate carcinoma in primary and biochemical recurrence.

Purpose: Prostate specific membrane antigen (PSMA) -ligand PET/CT is performed in patients with prostate cancer to stage the disease initially or to identify sites of recurrence after definitive therapy. 18F-PSMA-1007 is a promising PSMA-PET tracer based on clinical results, but detailed histologic confirmation has been lacking. Experimental Design: 96 patients with prostate cancer received a 18F-PSMA-1007-PET/CT followed by either radical prostatectomy with lymphadenectomy or salvage lymphadenectomy. The histological findings of PSMA-PET-positive nodes were analysed retrospectively. A lesion and a patient-based analysis was performed comparing 1) all positive and 2) only lesions with a size larger than 3 mm in histopathology. Results: 90.6% of the patients received 18F-PSMA-1007-PET/CT for staging before the primary treatment, while 9.4 % of the cohort underwent imaging for biochemical recurrence. In 34.4% of the cohort positive lymph nodes were present in imaging. A total of 1746 lymph nodes were dissected in 96 patients. 18F-PSMA-1007-PET had a lesion-based sensitivity of 81.7% a specificity of 99.6%, a positive predictive value (PPV) of 92.4%, a negative predictive value (NPV) of 98.9% for detecting positive lymph nodes larger than 3 mm. In the analysis of all malignant nodes regardless the size the overall sensitivity, specificity, PPV, and NPV on lesion-based analysis was 71.2%, 99.5%, 91.3%, and 97.9%, respectively. The patient-based analysis showed a sensitivity of 85.9% and a specificity of 99.5% for lymph nodes \u003e3 mm. Conclusion:18F-PSMA-1007-PET/CT reliably detects malignant lymph nodes and has an exceptional specificity of \u003e99% for nodal metastases.