In primary lymph nodal staging of patients with high-risk and intermediate-risk prostate cancer, how critical is the role of Gallium-68 prostate-specific membrane antigen PET computed tomography?

OBJECTIVE: To assess the diagnostic performance of Gallium-68 prostate-specific membrane antigen positron emission tomography-computed tomography (Ga-PSMA PET-CT) in primary lymphnodal staging of patients with intermediate-risk and high-risk prostate cancer and to compare it with multiparametric MRI (mp-MRI) whenever available. MATERIALS AND METHODS: Ga-PSMA PET-CT scans of 51 patients (average age 66.0 +/- 7.0 years) with biopsy-proven intermediate-risk and high-risk prostatic cancer who were managed by radical prostatectomy and extended pelvic lymph nodal dissection were retrospectively analyzed. Diagnostic performance of Ga-PSMA PET-CT in primary lymph nodal staging was analyzed using histopathology as reference. Diagnostic performance of mp-MRI, which was available in 35/51 patients was compared with that of Ga-PSMA PET-CT. RESULTS: Univariate analysis of patient characteristics showed significant influence of the pathological T-stage and maximum standard uptake value (SUV)max of the primary lesion on presence of nodal metastasis. In 51 patients, for patient-based analysis, the sensitivity, specificity and accuracy of Ga-PSMA PET-CT in detecting lymphnodal metastases were 80, 90.3 and 86.3%, respectively, and for lesion-based analysis 69.2, 99.6 and 98.4%, respectively. In 35/51 patients (who also had undergone mp-MRI), the patient-based and lesion-based sensitivity, specificity, and accuracy of Ga-PSMA PET-CT were 81.3, 84.2, 82.8% and 70.9, 99.5, 98.2%, respectively, and that of mp-MRI were 43.7, 78.9, 62.8% and 32.2, 98.5, 95.5%, respectively. For lesion-based analysis, Ga-PSMA PET-CT performed better than mp-MRI (P value = 0.04). CONCLUSION: Ga-PSMA PET-CT allows accurate detection of lymphnodal metastases in patients with intermediate-risk and high-risk prostate cancer prior to definitive surgical treatment. It performed better than mp-MRI in a subset of patients.