Fluorescence Lymph Node Mapping Using ICG Improves Lateral Lymph Node Dissection for Mid-Low Rectal Cancer: A Propensity Score-Matched Cohort

Background: Patients with lateral lymph node metastasis (LLNM) present particular challenges for both diagnosis and treatment. This study aimed to assess whether indocyanine green (ICG) assisted lymph node mapping with near-infrared imaging (NIRI) enhances the effectiveness of lateral lymph node dissection (LLND) by further categorizing the lateral lymph nodes in patients with mid-low rectal cancer. Methods: Submucosal indocyanine green injection was performed on the distal margin of the rectal cancer. In the ICG-LLND group, the lymphatic drainage pathway and distribution of lateral lymph nodes (LLNs) were explored using a laparoscopic NIRI system. Pathological evaluations were conducted for both the ICG-LLND group and the control group. Results: The ICG-LLND group demonstrated a significantly shorter postoperative hospital stay compared to the control group, both before (P<0.001) and after (P=0.001) matching. While blood loss and operating time were similar between groups, the ICG-LLND group had fewer cases of anastomotic leakage (P=0.206). Postoperative lymph node harvesting was significantly higher in the ICG-LLND group, with more total lymph nodes (P=0.001) and lateral lymph nodes (P=0.002) harvested. The number of harvested lymph nodes in the obturator and internal iliac regions was also higher in the ICG-LLND group (P=0.001), and the number of positive lymph nodes in these regions was significantly greater before (P=0.027) and after (P=0.013) matching. Univariate and multivariate analyses showed that ICG-LLND, nCRT, and positive pN stage were associated with increased lymph node harvest. Conclusions: ICG-LLND improved lateral lymph node harvest, particularly obturator lymph nodes, and shortened postoperative hospital stay without increasing complications. This technique may enhance surgical outcomes in patients requiring lymph node dissection.