How accurate is 68 Gallium-prostate specific membrane antigen positron emission tomography / computed tomography ( 68 Ga-PSMA PET/CT) on primary lymph node staging before radical prostatectomy in intermediate and high risk prostate cancer? A study of patient- and lymph node- based analyses.

Background and Aim: Gallium-68 (68Ga)-Prostate Membrane Specific Antigen Positron Emission Tomography/Computed Tomography (68Ga-PSMA PET/CT) is an emerging diagnostic modality which is gaining importance in individualized prostate cancer (PCa) management era. This study aimed to investigate the diagnostic accuracy of ⁶⁸ Ga-PSMA PET/CT on primary LN staging before radical prostatectomy (RP) in intermediate and high risk PCa.
Materials and Methods: The retrospectively documented 49 patients with intermediate and high risk non-metastatic PCa who had ⁶⁸ Ga-PSMA PET/CT before RP were enrolled into this study. The histopathology of dissected LNs was used as reference standard to evaluate the accuracy of ⁶⁸ Ga-PSMA PET/CT on primary LN staging, both in per-patient (n = 49) and in per-node (n = 454) analyses. The diagnostic accuracy was investigated using sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), and by area under the curve (AUC) provided using receiver operating curve (ROC) analysis.
Results: Median age was 64 (48-79) years and, median and mean PSA values were 10 (1.31-138) ng/ml and 16.2 (±19.8) ng/ml, respectively. 22 (44.9%) and 27 (55.1%) of patients had intermediate and high risk PCa, respectively. A total of 5 (10.2%) patients had histopathologically proven LN metastasis and 3 (60%) of them was detected in ⁶⁸ Ga-PSMA PET/CT. In per patient analysis, the sensitivity, specifity, PPV and NPV of ⁶⁸ Ga-PSMA PET/CT on primary LN staging were 0.60, 0.96, 0.60 and 0.96, respectively. Among overall 454 LNs, 16 (3.5 %) of them were reported as metastatic in histopathology and, 13 (2.9%) of these metastatic LNs were detected in ⁶⁸ Ga-PSMA PET/CT. In per-node analysis, the sensitivity, specificity, PPV and NPV of ⁶⁸ Ga-PSMA PET/CT on primary LN staging were 0.82, 0.99, 0.87 and 0.99, respectively. The ROC analyses found AUCs for primary LN staging as 0.777 (95%CI:0.508-1.0) in per patient analysis and, as 0.904 (95%CI:0.790 - 1.0) in per node analysis, respectively.
Conclusion: The use of ⁶⁸ Ga-PSMA PET/CT has promising diagnostic accuracy on primary LN staging before RP in intermediate and high risk PCa. However, the efforts should be taken to increase sensitivity of ⁶⁸ Ga-PSMA PET/CT in individualized treatment era.
Competing Interests: Conflict of interest All authors declare that they have no conflict of interest
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