Introduction: Sentinel lymph node dissection (SLND) has the potential to improve the accuracy of staging prostate cancer (PCa) patients. Conventional rigid laparoscopic gamma probes (RLGPs) have limited maneuverability and control. To address these limitations our group have developed a tethered laparoscopic drop-in gamma probe called SENSEI®. An ongoing prospective, international, multicenter clinical trial evaluates SENSEI® for SLND in PCa patients (ClinicalTrials.gov: NCT04632251). Here we present the interim results.
Methods: The SENSEI® probe fits through a standard 12 mm port and is grasped by standard surgical instruments for autonomous control by the surgeon with unprecedented rotational freedom. The numerical and audible read out of the Control Unit can be integrated in the TileProTM.
Following local ethics approval (2020/9128) and informed consent, patients eligible for radical prostatectomy (RP) + extended pelvic lymphadenectomy (ePLND) had a transrectal injection of 99mTc-nanocolloid in each quadrant of the prostate the day before surgery and subsequent lymphoscintigraphy scans. Manual laparoscopic or robot-assisted RP was performed the next day, followed by SLND. SLN detection was performed using SENSEI® and a RLGP. An ePLND was completed after SLND. Safety was monitored until discharge or up to one week after surgery.
Results: 8 patients underwent manual laparoscopic and 2 patients robot-assisted surgery. SENSEI® successfully detected a SLN in all 10 patients (detection rate: 100%). The total number of SLNs identified with SENSEI® was 27 (median 2 per patient, range 1 – 6). 1 SLN was located outside of the ePLND template in the left presacral area.
The RLGP was used in 8 patients undergoing manual laparoscopy. The total number of SLNs identified with the RLGP was 17 (median 2, range 1 – 4). 2 SLNs identified by SENSEI® in the right internal iliac and left presacral region respectively could not be detected with the RLGP due to the inability to precisely position the RLGP in these anatomically restricted areas.
Histopathology identified 4 patients with positive nodes. All 4 had at least one metastatic SLN identified with SENSEI®. No false-negative or false-positive cases occurred. The RLGP also detected all LN-positive patients. A total of 32 SLNs were found in the excised SLN specimens (median 3 SLNs per patient, range 1 – 8) and 190 LNs were present in the excised ePLND specimens (median 18 LNs per patient, range 11 – 27). No adverse events related to the SLND procedure or SENSEI® device occurred.
Conclusions: SENSEI® enables successful detection of SLNs in a minimally invasive setting with the potential for improved SLND compared with the RLGP, and more accurate LN staging if confirmed by the final results which are expected in Q1 2022. Future applications include the use of SENSEI® in combination with 99mTc-PSMA for intraoperative detection of LN metastases.
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