Prospective evaluation of 68Gallium-prostate-specific membrane antigen positron emission tomography/computed tomography for preoperative lymph node staging in prostate cancer

Objectives: To assess the accuracy of 68Gallium-prostate-specific membrane antigen (68Ga-PSMA) positron emission tomography/computed tomography (PET/CT) for lymph node (LN) staging in intermediate- and high-risk prostate cancer (PCa). Materials and Methods: From April to October 2015, 30 patients with intermediate- (n = 3) or high-risk (n = 27) PCa were prospectively enrolled. Patients underwent preoperative 68Ga-PSMA PET/CT. Both visual and semi-quantitative analyses were undertaken. Subsequently, all patients underwent radical prostatectomy (RP) with an extended pelvic lymph node dissection. The sensitivity, specificity, and positive (PPV) and negative predictive value (NPV) for LN status of 68Ga-PSMA were calculated using histopathology as reference. Results: Eleven patients (37%) had lymph node metastases (LNMs); 26 LNMs were identified in the 11 patients. Patient analysis showed that 68Ga-PSMA PET/CT had a sensitivity of 64% for the detection of LNMs, its specificity was 95%, the PPV was 88%, and the NPV was 82%. In total, 180 LN fields were analysed. In the LN-region-based analysis, the sensitivity of 68Ga-PSMA PET/CT for detection of LNMs was 56%, the specificity was 98%, the PPV was 90% and the NPV was 94%. The mean size of missed LNMs was 2.7 mm. Receiver-operating characteristic curve analysis showed a high accuracy of maximum standardized uptake value (SUV_max) for the detection of LNMs, with an area under the curve of 0.915 (95% confidence interval 0.847–0.983); the optimum SUV_max was 2.0. Conclusions: In patients with intermediate- to high-risk PCa, 68Ga-PSMA PET/CT had a high specificity and a moderate sensitivity for LNM detection. 68Ga-PSMA PET/CT had the potential to replace current imaging for LN staging of patients with PCa scheduled for RP.