Indocyanine green-guided robotic-assisted mesorectal lymphadenectomy for high-risk T1 rectal carcinoma: Preliminary results of a prospective cohort study (IDEAL stage 2a).

Abstract

Lymph node metastases occur in 10%-15% of high-risk T1 rectal tumours. Total mesorectal excision remains the standard treatment, whereas chemoradiotherapy is reserved for patients with frailty. Indocyanine green (ICG)-guided lymphadenectomy may represent an organ-preserving alternative for patients at high risk of node metastasis. From May 2021 to July 2025, 11 patients underwent curative transanal excision surgery for early-stage low rectal cancer that was classified as high-risk pT1 adenocarcinoma. ICG (1 mg) was injected submucosally to label all lymph nodes irrespective of their metastatic status. ICG-guided robotic-assisted mesorectal lymphadenectomy was performed with the Firefly Imaging System (INTUITIVE©). Initially, ICG was injected intraoperatively (n = 2 patients). However, due to unsuccessful mapping in the second patient, ICG was then administered the day before surgery in all subsequent patients, resulting in successful visualisation and excision. Lymphatic drainage was not along the superior rectal artery in two patients. Lymphadenectomy was mainly performed along the superior rectal artery to its bifurcation into the right and left rectal arteries in the mid-rectum. The median number of excised lymph nodes was 16.7 (range: 9-29). Lymph node invasion was detected in one patient who then received adjuvant chemotherapy. The median hospital stay was 2 days, without complications. After 36 months of follow-up (range: 12-60), all patients were alive without disease progression or functional impairment. In patients with early T1 rectal tumours, ICG-guided robotic-assisted mesorectal lymphadenectomy seems to be technically feasible. These preliminary results, feasibility and oncological safety need to be confirmed in a prospective multicentre trial.