In this prospective randomized study, patients with early biochemical recurrence after radical prostatectomy and with PSMA-PET positive unilateral pelvic metastatic lesions are assessed as to whether unilateral and bilateral salvage lymph node dissection are oncologically equivalent. For this, the following endpoints will be evaluated:

• complete biochemical response (cBR: PSA <0.2ng /ml) after salvage lymph node dissection
• biochemical freedom from recurrence without further prostate-cancer-specific therapy (time from salvage lymph node dissection to first PSA value> 0.2ng / ml)
• prostate cancer-specific therapy-free time (time from salvage lymph node dissection to initiation of prostate cancer specific therapy) In addition, the diagnostic accuracy of the preoperative PSMA PET, which led to the indication of salvage lymph node dissection, is to be investigated in the context of the study and the standardized one- or two-sided template lymph node dissection. Furthermore, it should be investigated whether there is a reduction of surgery-associated side effects in patients undergoing unilateral salvage lymph node dissection. In addition, quality of life and psychological stress of patients is systematically recorded by means of validated questionnaires. Since salvage lymph node dissection may also be carried out with the help of currently experimental preoperative labeling with PSMA ligands for easier intraoperative localization (PSMA radioguided surgery), a comparison of conventional salvage surgery and the PSMA radioguided surgery is also planned. However, if applied to patients, PSMA radioguided surgery is performed outside of the study protocol and is explicitly not part of the study protocol.

In case there is no complete biochemical response (cBR, PSA <0.2ng / ml) or, after reaching cBR, a further increase in PSA above 0.2ng / ml threshold is observed after salvage lymph node dissection, an attempt should be made to localize recurrence disease using PSMA PET. This should provide indirect information as to whether re-irradiation following salvage lymph node dissection could be a useful approach and should be investigated in future studies. However, PSMA PET is recommended in the study, but is optional and therefore to be performed outside of the study protocol.