# Lymph node mapping-based optimal bowel-resection margin and central radicality in colon cancer surgery: an international, prospective, observational cohort study

## TL;DR

This study finds that a '10-cm rule' could guide bowel resection in colon cancer surgery, with no ethnic differences in lymph node spread patterns.

## Contribution

First multinational study mapping lymph node spread in colon cancer patients from Western and Eastern populations.

## Key findings

- The '10-cm rule' is a potential international standard for bowel resection margins.
- Metastatic lymph node incidence in central LNs is low and varies by tumor stage and location.
- Complete removal of intermediate lymph nodes is recommended even for early-stage tumors.

## Abstract

Substantial variations in the extent of lymphadenectomy are acknowledged internationally in colon cancer surgery because essential data for standardization, including the anatomical distribution of metastatic lymph nodes (LN), are lacking.

Pre-specified LN mappings based on in vivo bowel measurements were conducted for stages I-III colon cancer patients treated at 31 leading hospitals in six countries. The extent of lymphadenectomy was classified from levels A (pericolic) to C (central LNs) according to the pre-specified anatomical landmarks. The primary outcome was the extent of pericolic lymphatic spread and the incidence of metastasis in central LNs, and secondary ones included the real-world status of central radicality and its association with short-term outcomes.

Among 3647 patients, pericolic spread beyond 10 cm (0.2%) and absence of feeding arteries supplying the bowel within 10 cm from the primary tumor (0.3%) were rare, irrespective of nationality. The incidence of metastasis in central LNs was ∼3% (range: 0.2% in T1 to 7% in T4 tumors) and was lower in tumors located at the splenic flexure (0.5%). The proportion of patients with level C radicality was ∼76%, which was statistically significantly associated with T stage only in one country. A higher radicality level conferred no adverse impact on either the incidence of Clavien–Dindo grade ≥III or 30-day mortality.

The ‘10-cm rule’ could be an international criterion for determining the bowel-resection margin. Central lymphadenectomy is feasible internationally, though the indication should be selective, not routine, depending on the stage and location of the primary tumor.

ICA, ileocolic artery; IMA, inferior mesenteric artery; LCA, left colic artery; MCA, middle colic artery; RCA, right colic artery; SA, sigmoid artery; SMA, superior mesenteric artery; SMV, superior mesenteric vein.

•This is the first multi-national study for LN mapping with Western and Eastern populations of colon cancer patients.•There is no ethnic difference in the anatomical distribution of metastatic LNs and feeding arteries.•The ‘10-cm rule’ could be an optimal international criterion for determining the bowel-resection margin.•Complete removal of intermediate LNs is imperative even for T1 or T2 tumors considering the incidence of metastatic tumors.•The indication of central LN dissection should be tailored, most preferably by T stage and tumor location.

This is the first multi-national study for LN mapping with Western and Eastern populations of colon cancer patients.

There is no ethnic difference in the anatomical distribution of metastatic LNs and feeding arteries.

The ‘10-cm rule’ could be an optimal international criterion for determining the bowel-resection margin.

Complete removal of intermediate LNs is imperative even for T1 or T2 tumors considering the incidence of metastatic tumors.

The indication of central LN dissection should be tailored, most preferably by T stage and tumor location.