S122: impact of fluorescence and 3D images to completeness of lateral pelvic node dissection

Lateral pelvic lymph node dissection (LPND) is a technically demanding procedure. Consequently, there is a possibility of incomplete dissection of lateral pelvic lymph nodes (LPNs). We aimed to identify metastatic LPNs intraoperatively in real-time under dual guidance of fluorescence imaging and 3D lymphovascular reconstruction, and then to remove them completely.

Rectal cancer patients who were scheduled to undergo LPND after preoperative chemoradiotherapy (CRT) were prospectively enrolled. We traced changes in suspected metastatic LPNs during preoperative CRT and defined them as index LPNs on post-CRT imaging studies. For fluorescence imaging, indocyanine green (ICG) at a dose of 2.5 mg was injected transanally around the tumor before the operation. For 3D reconstruction images, each patient underwent preoperative axial CT scan with contrast (0.6 mm slice thickness). These images were then manipulated with OsiriX. Index LPNs and essential structures in the pelvic sidewall, such as the obturator nerve, were reconstructed with abdominal arteries from 3D volume rendering. All surgical procedures were performed via laparoscopic or robotic approach.

From March to July 2017, ten rectal cancer patients underwent total mesorectal excision with LPND after preoperative CRT under dual image guidance. Bilateral LPND was performed in five patients. All index LPNs among ICG-bearing lymph nodes were clearly identified intraoperatively by matching with their corresponding 3D images. Pathologic LPN metastasis was confirmed in four patients (40.0%) and in five of the 15 dissected pelvic sidewalls (33.0%). All metastatic LPNs were identified among index LPNs. Four (80.0%) of the five metastatic LPNs were located in the internal iliac area.

Index LPNs among ICG-bearing lymph nodes in pelvic sidewall were clearly identified and completely removed by matching with their corresponding 3D reconstruction images. Further studies and long-term oncologic outcomes are required to determine the real impact of dual image guidance in LPND.