Prostate-specific Membrane Antigen–radioguided Surgery for Metastatic Lymph Nodes in Prostate Cancer

With the advent of 68Ga-labeled prostate-specific membrane antigen-N,N′-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N′-diacetic acid (68Ga-PSMA-HBED-CC) positron emission tomography (PET) hybrid imaging in prostate cancer (PCa), even small metastatic lymph nodes (LNs) can be visualized. However, intraoperative detection of such LNs may not be easy owing to their inconspicuous morphology and/or atypical localization. The aim of our feasibility study was to evaluate PSMA-radioguided surgery for detection of metastatic LNs. One patient with primary PCa and evidence of LN metastases and four PCa patients with evidence of recurrent disease to regional LNs on 68Ga-PSMA-HBED-CC PET hybrid imaging received an intravenous injection of an 111In-PSMA investigation and therapy agent 24 h before surgery. Metastatic LNs were tracked intraoperatively using a gamma probe with acoustic and visual feedback. All radioactive-positive LN specimens detected in vivo were confirmed by ex vivo measurements and corresponded to PSMA-avid metastatic disease according to histopathology analysis. Intraoperative use of the gamma probe detected all PSMA-positive lesions identified on preoperative 68Ga-PSMA-HBED-CC PET. Detection of small subcentimeter metastatic LNs was facilitated, and PSMA-radioguided surgery in two patients revealed additional lesions close to known tumor deposits that were not detected by preoperative 68Ga-PSMA-HBED-CC PET. However, greater patient numbers and long-term follow-up data are needed to determine the future role of PSMA-radioguided surgery.