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Optimal Bowel Resection Margin in Colon Cancer Surgery: Prospective Lymph Node Mapping in 2,996 Colon Cancer Patients

Background: There are no standardised criteria for the determination of the ‘regional’ pericolic node in colon cancer surgery, which represents a major cause of the international uncertainty regarding the optimal bowel resection margin. This prospective cohort study aimed to determine ‘regional’ pericolic nodes based on detailed mapping for feeding arteries and lymph nodes. 
 
Methods: In all, 2,996 patients with stages I–III colon cancer who underwent curative surgery between June 2013 and December 2017 at 25 institutions in Japan were included. The anatomical distributions of the feeding artery and lymph nodes were determined in resected fresh surgical specimens based on in vivo measurements of the bowel. 
 
Findings: The mean number of retrieved pericolic nodes was 20·9 per patient. In all patients except seven (0·2%), the primary feeding artery was distributed within 10 cm of the primary tumour. The metastatic pericolic node location most distant from the primary tumour was within 3 cm in 837 patients, 3–5 cm in 130 patients, 5–7 cm in 39 patients and 7–10 cm in 34 patients. Only four patients (0·1%) had pericolic lymphatic spread beyond 10 cm; all of whom had T3/4 tumours accompanying extensive mesenteric lymphatic spread, and three developed systemic recurrence. The positive pericolic node distance from the primary tumour did not differ depending on the primary tumour location or the distribution of the feeding arteries. Postoperatively, none of the 2996 patients developed recurrence in the remaining pericolic nodes. 
 
Interpretation: Based on the distribution of metastatic lymph nodes and prognostic outcomes, the pericolic nodes designated as ‘regional’ were those located within 10 cm of the primary tumours. Despite the fact that surgeons tend to prefer complete mesocolic excision, these findings should be fully considered when determining the bowel resection margin. 
 
Funding: Japanese Society for Cancer of the Colon and Rectum 
 
Declaration of Interest: All authors declare no competing interests. 
 
Ethical Approval: This study was conducted according to the Declaration of Helsinki and comparable Japanese ethical standards. The study was approved by the Institutional Review Boards of the JSCCR and each participating institution. Written informed consent was obtained from all study participants