The diagnostic accuracy of 68Ga-PSMA-PET/CT in primary staging of patients with high-risk nonmetastatic prostate cancer treated with radical prostatectomy: A single-center cohort analysis

Background: Ga-68-prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) is a recommended imaging modality for patients with recurrent prostate cancer (PCa). Its routine implementation before radical prostatectomy (RP) may allow avoiding undertreatment. We aimed to analyze the diagnostic accuracy of Ga-68-PSMA-PET/CT for pelvic lymph node metastases in a large cohort of patients treated with RP and extended pelvic lymph node dissection (ePLND) for high-risk PCa.Methods: This is a retrospective analysis of an institutional database of patients who underwent Ga-68-PSMA-PET/CT before RP and ePLND for high-risk PCa. The diagnostic estimates of Ga-68-PSMA-PET/CT with 95% confidence intervals (CIs) for lymph node involvement were calculated.Results: We included 165 high-risk PCa patients. The median PSA value was 24.5 ng/mL (range: 6.7-185) and all the patients had biopsy Grade Group 4-5. In total, 46 (28%) of patients had clinical lymph node involvement at Ga-68-PSMA-PET/CT. A mean number of resected lymph nodes per patient was 22 (range: 15-45) and 149 (4.2%) of all resected nodes were positive for lymph node metastasis at final pathology. The diagnostic estimates for the detection of pN+ disease at RP were as follows: sensitivity 63% (95% CI: 51-75), specificity 97% (95% CI: 91-99), positive predictive value 94% (95% CI: 82-99), and negative predictive value 79% (95% CI: 70-86). The total accuracy of PSMA-PET was 83% (95% CI: 76-88).Conclusion: Our analyses support high specificity and positive predictive value of pretreatment Ga-68-PSMA PET/CT for the detection of pelvic lymph node metastasis in patients treated with RP for high-risk PCa. While a positive finding should be considered as robust indicator for clinical decision-making, a negative result cannot reliably rule out the presence of lymph node involvement in high-risk PCa; there is a need for advanced risk stratification in those patients.