Indocyanine Green Lymphatic Mapping in Minimally Invasive Sigmoid and Rectal Cancer Surgery

Background and Rationale

Adequate lymphadenectomy is a fundamental component of curative-intent surgery for colorectal cancer. Accurate pathological assessment of regional lymph nodes is essential for determining disease stage, guiding adjuvant treatment, and estimating prognosis. Retrieval and examination of at least 12 lymph nodes is widely accepted as a benchmark for adequate nodal staging.

Nevertheless, lymph node yield may vary according to patient characteristics, tumor location, previous neoadjuvant treatment, surgical technique, and pathological assessment.

Indocyanine green-guided lymphatic mapping (ICG-LM) is a fluorescence-guided surgical technique that enables visualization of lymphatic drainage pathways using near-infrared imaging. By identifying fluorescent lymphatic structures and lymph nodes, this approach may improve intraoperative recognition of lymphatic drainage patterns and facilitate lymph node retrieval.

Study Design and Population

This was a prospective, single-center, non-randomized comparative study with a historical control group, conducted at the University Hospital in Krakow, Poland.

The study included patients undergoing minimally invasive oncological resection for sigmoid colon or rectal adenocarcinoma.

The intervention group consisted of prospectively enrolled patients who underwent indocyanine green-guided lymphatic mapping during minimally invasive colorectal cancer surgery.

The historical control group consisted of patients who had previously undergone standard minimally invasive oncological resection without ICG-guided lymphatic mapping. Clinical and perioperative data from the historical cohort were used for comparative analysis.

No random allocation was performed.

ICG Administration and Fluorescence-Guided Surgery

Patients in the intervention group underwent intraoperative endoscopic administration of indocyanine green into the submucosal layer surrounding the tumor.

The administered dose was 2.5 mg of ICG, corresponding to 2 mL of a solution with a concentration of 1.25 mg/mL.

During minimally invasive surgery, near-infrared fluorescence imaging was used to visualize lymphatic drainage pathways and fluorescent lymph nodes.

Standard oncological resection and lymphadenectomy were performed according to established surgical principles. Fluorescence imaging served as an adjunct to conventional anatomical dissection rather than a replacement for standard oncological surgery.

The fluorescence-guided technique allowed the surgical team to assess lymphatic drainage patterns and identify potentially relevant lymph nodes.

Study Outcomes

The principal outcome of the comparative analysis was the adequacy of lymphadenectomy, assessed by the proportion of patients with an inadequate lymph node yield, defined as fewer than 12 lymph nodes retrieved and identified during histopathological examination of the surgical specimen.

Additional outcomes included total lymph node yield, the number of metastatic lymph nodes, operative time, and postoperative outcomes, including complications and recovery parameters.

The study also evaluated the technical feasibility of fluorescence-guided lymphatic mapping and the intraoperative visualization of lymphatic drainage pathways.

Statistical Analysis

Because treatment allocation was not randomized and the control group was historical, propensity score-based methods were applied to reduce the influence of differences in baseline patient characteristics.

Propensity score matching (PSM) was performed to construct comparable groups based on relevant demographic and clinical characteristics.

The primary outcome was evaluated by comparing the proportion of patients with fewer than 12 retrieved lymph nodes between the ICG-LM and control groups. Effect estimates were expressed using appropriate measures of association and 95% confidence intervals.

An additional analysis using propensity score overlap weighting was performed to assess the robustness of the findings and improve comparability between treatment groups.

Secondary outcomes were compared using statistical methods appropriate to the type and distribution of each variable.

Study Significance

This study investigated the clinical utility of indocyanine green-guided lymphatic mapping in minimally invasive oncological surgery for sigmoid colon and rectal cancer.

By comparing prospectively enrolled patients undergoing fluorescence-guided surgery with a historical control cohort, the study sought to provide preliminary evidence regarding the relationship between fluorescence-guided lymphatic mapping, adequacy of lymphadenectomy, and perioperative outcomes.