Session: MP61: Prostate Cancer: Localized: Surgical Therapy II
MP61-14: PSMA Radio-Guided Surgery to Detect Nodal Metastases in Prostate Cancer Patients Undergoing Robot-assisted Radical Prostatectomy and Extended Pelvic Lymph Node Dissection: Updated Results of Planned Interim Analyses of a Prospective Phase 2 Study.
Introduction: Extended pelvic nodal dissection (ePLND) represents the gold standard for nodal staging in prostate cancer (PCa). Prostate-specific membrane antigen radio-guided surgery (PSMA-RGS) could identify lymph node invasion (LNI) during robot-assisted radical prostatectomy (RARP). We aim at reporting the updated results of interim analyses of a phase 2, prospective, single center study (NCT04832958) aimed at describing the feasibility and accuracy of PSMA-RGS during RARP Methods: 21 elegible patients with intermediate- or high-risk cN0cM0 prostate cancer at conventional imaging with a risk of LNI >5% at a single centre were enrolled. Among those, 18 patients underwent PSMA-RGS between June 2021 and September 2022. All patients received a 68Ga-PSMA PET preoperatively. 99mTc-PSMA I&S was synthesized and administered intravenously the day before surgery (median activity: 735 MBq) followed by SPECT/CT. A drop-in gamma probe was used for in-vivo and ex-vivo measurements during PSMA-RGS. All positive lesions (count rate =2 compared to background) were excised and an ePLND was performed. The ePLND included obturator, internal, external and common iliac nodal regions. Side effects, perioperative outcomes, and accuracy of PSMA-RGS for LNI at final pathology were evaluated. Results: Overall, 6 (33%), 8 (50%) and 4 (17%) patients had intermediate-risk, high-risk, and locally advanced PCa. 7 (38%) patients had nodal uptake at PSMA PET/MRI. No adverse events were recorded after 99mTc-PSMA administration. Median operative time, blood loss and leght of stay were 218 min, 100 mL and 4 says, respectively. No intraop complications were recorded. One patient experienced a 30-day complication (Clavien-Dindo 2). A total of 116 pelvic nodal specimens were resected, which included 446 nodes (median 22 per patient). Overall, 5 (27%) patients had LNI (median 3 positive LN per patient). At a per-region analysis combining both in-vivo and ex-vivo measurements, PSMA-RGS had sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of 70%, 45%, 86% and 94%, respectively. At per-patient level, the same figures for PSMA-RGS were 100%, 61%, 50% and 100% respectively. Conclusions: Our updated results confirm that 99mTc-PSMA-RGS during RARP is a safe and feasible procedure characterized by an excellent sensitivity and NPV but suboptimal PPV in a per-patient level analysis using a target-to-background count rate =2. SOURCE OF Funding: none
