Indocyanine green fluorescence-guided lymphatic mapping improves central nodes dissection and survival in left-sided colon cancer and rectal cancer: a prospective cohort study.

[BACKGROUND] Radical lymphadenectomy is essential for the long-term outcomes of colorectal cancer (CRC). However, the exact distribution and drainage patterns of central lymph nodes in left-sided colon cancer and rectal cancer remain unclear. This study aimed to map apical lymph node distribution using intraoperative Indocyanine green (ICG) fluorescence imaging and to evaluate the superiority of fluorescence-guided lymph node dissection in CRC surgery.

[METHODS] We conducted a prospective, propensity score-matched comparative study involving patients who underwent laparoscopic surgery for left-sided colon cancer and rectal cancer. The patients were assigned to either ICG fluorescence-guided or conventional laparoscopic surgery. Lymph node yield, short-term perioperative outcomes, and long-term survival were compared between groups. The central lymph node distribution patterns in the ICG group were analyzed.

[RESULTS] After propensity score matching, a total of 180 patients were enrolled, with 60 and 120 patients in the ICG and control groups, respectively. The ICG group had a significantly higher median number of retrieved lymph nodes [20.8 (7.9) vs 16.3 (7.1), P < 0.001] and a significantly lower postoperative complication rate (11.7% vs 17.5%, P = 0.01). Importantly, ICG-guided surgery was associated with a reduced risk of inadequate lymph nodes retrieval and was identified as an independent prognostic factor of overall survival (hazard ratio = 2.544, 95% CI: 1.088-5.948, P = 0.031). ICG imaging revealed that central lymphatic drainage patterns were highly personalized. Over 95% of apical lymph nodes located within 2.2 cm on the left side of the IMA, 1.3 cm on the right side and 0.9 cm from the root of the IMA, and additional atypical drainage pathways - including to the iliac region - were observed in select cases.

[CONCLUSIONS] ICG fluorescence-guided surgery improves the accuracy and extent of lymph node dissection in left-sided colon cancer and rectal cancer, reduces the risk of inadequate retrieval, and is independently associated with improved long-term survival. These findings support the integration of ICG-guided lymphadenectomy as a promising procedure for CRC.