Objectives：The aim of this prospective study was to evaluate the clinical value of ⁶⁸Ga-PSMA-11 PET/CT in the staging and risk stratification of therapy naïve prostate cancer (PCA) and metastatic castrate resistant prostate cancer (mCRPC).

Methods: Consecutive18 patients with mCRPC, and 22 naïve diagnosed consecutive patents with PCA were enrolled in this study. ⁶⁸Ga-PSMA-11 PET/CT and MRI was performed in all patients for the evaluation of prostatic primary lesion, final diagnosis was confirmed by pathology and clinical follow-up. The expression of prostate-specific membrane antigen (PSMA) on the primary lesion was analyzed by tissue analysis. Results: Out of 40 patients, 37 patients (15 mCRPC, and 22 naïve diagnosed PCA) accounting for 92.5% showed PSMA-avid lesion in ⁶⁸Ga-PSMA-11 image. Only 3 patients with mCRPC in stable disease after chemotherapy were negative. The sensitivity, specificity and accuracy of ⁶⁸Ga-PSMA-11 imaging was 97.3%, 100.0% and 97.5%, respectively. Of the 22 patients with naïve prostate cancer, the standardized uptake value (SUV_max) of primary prostatic lesion was 17.09±11.08, whereas it was 13.33 ± 12.31 for the mCRPC group. ⁶⁸Ga-PSMA-11 detected 15 patients with lymph node metastasis, a total of 105 metastatic lymph nodule were visualized, SUV_max in naïve prostate cancer was 16.85± 9.70, whereas that of mCRPC was 7.54±5.20.Twenty nine patients with bone metastasis，SUVmax was 27.57±19.71.

Conclusion: ⁶⁸Ga-PSMA-11 PET/CT is of great value for the diagnosis, staging and risk stratification of therapy naïve prostate cancer patients, and has greater advantage in detection of lymph node and remote metastasis in mCRPC. ⁶⁸Ga-PSMA-11 PET/CT may have great potential for staging and guiding PSMA-based targeted therapy which needs to be confirmed by prospective larger-cohort studies.