e591 Background: PSMA-PET/CT is the most sensitive diagnostic tool in biochemical recurrent prostate cancer to detect minimal metastatic disease. However, it may be difficult to localize small PSMA-positive lymph nodes intraoperatively. Therefore, it was the aim to investigate whether preoperative Tc-99m-PSMA targeting may improve intraoperative tumor localization by use of a gamma probe. Methods: In 13 Patients Ga-68-PSMA-PET/CT identified iliac lymph nodes in patients suitable for salvage lymph node dissection. On the day before operation a mean activity of 480 MBq Tc-99m-PSMA was injected and gamma camera scintigraphy + SPECT was performed 4-5 hours after tracer application. About 24 hours after tracer application a salvage lymph node dissection was performed on the side of initial suspicious lymph node metastases. Sensitivity, specifity, pos and neg. predictive values were calulated for PSMA-PET/CT and gamma probe use to analyse the additional use. Results: In 9 / 13 patients PSMA-positive metastatic lymph nodes were identified in Ga-68 PSMA-PET/CT. A total of 156 lymph nodes were removed with 14 lymph nodes in 9 patients being positive in histopathologic examination. Sensitivity, specifity, pos and neg. predictive values for PSMA PET/CT and gamma probe were 85% and 79%, 99% and 100%, 85% and 100% and 99% and 98% respectively. In one patient only gamma probe use identified a pathologic lymph node. Conclusions: Gamma probe guided salvage lymph node dissection in PSA recurrent prostate cancer is feasible and had a high concordance with PSMA-PET/CT. However, the additional diagnostic benefit is limited compared to PSMA-PET/CT because in only one patient (7%) a positive lymph node could be identified with the use of the gamma probe outside the standard operative area in salvage lymph node dissection.
Whether extended pelvic lymph node dissection should be performed in prostate cancer: The present evidence from a systematic review and meta‐analysis