99mTc-PSMA targeted robot-assisted radioguided surgery during radical prostatectomy and extended lymph node dissection of prostate cancer patients

Objective: The feasibility of tracer production of ^99mtechnetium (Tc)-prostate-specific membrane antigen (PSMA)—I&S sterile cold kit, imaging with single photon emission tomography/computed tomography (SPECT/CT), and ^99mTc-PSMA-radioguided robot-assisted laparoscopic radical prostatectomy (^99mTc-PSMA-RG-RALRP) technique for lymph node (LN) dissection of primary prostate cancer (PCa) patients were evaluated prospectively. Methods: Fifteen primary PCa patients with intermediate- or high-risk score according to D’Amico risk stratification who had PSMA receptor affinity with Ga-68 PSMA-11 PET/CT were enrolled. After ^99mTc-PSMA-I&S injection and SPECT/CT imaging, ^99mTc-PSMA-RG-RALRP with DaVinci XI robotic platform and laparoscopic gamma probe were performed. Radioactive rating of resected tissue was compared with post-operative histopathology. Physiological and pathological uptakes of organs and tissues for both imaging modalities were compared. Results: Physiological radiotracer distribution was similar for both imaging modalities. PCa lesions were much more visible on PET/CT. Metastatic LNs could not be visualized with SPECT/CT. Eighteen of 297 totally dissected LNs were metastatic, which were exactly the same with per-operative probe counts with sensitivity, specificity, accuracy, and negative and positive predictive value of all 100%. The median follow-up was 23.5 ± 4.6 months. tPSA reduction was > 98%. The 2.5 years biochemical recurrence-free survival, PCa-specific treatment-free survival and overall survival rates were 86,7%, 66,7% and 100%, respectively. Conclusion: Tc-99 m-PSMA-RG-RALRP is a promising technique for extended pelvic lymph node dissection (ePLND) during robotic surgery, which may shorten the operation time and reduce complication risks. If LN metastases is detected during surgery with PSMA-targeted probe, it may be an early indicator of PCa-spesific treatment planning. Tc-99 m-PSMA-I&S SPECT/CT is not as successful as Ga-68 PSMA-11 PET/CT for diagnosis of primary PCA lesions or LN metastases.