Background: The number of lymph node metastasis (LNM) is a strong prognostic factor in the treatment of colorectal cancer (CRC). However, the impact of the mesentery location on LNM remains unclear. We assessed the impact LNM location on the recurrence of stage III CRC. Methods: Subjects with CRC and pathologically positive LNM were enrolled retrospectively. We defined three groups: LNM adjacent to the tumour (group A), metastases with horizontal or vertical spread (group B), and metastases with both horizontal and vertical spread (group C). Recurrence-free survival (RFS) was the primary outcome measure used for the study. Results: A total of 241 (Group A: 121, B: 90, and C: 30) patients were recruited for the study. Multivariate analysis by Cox regression model indicated LNM location to be an independent predisposing risk factor for recurrence [group B: Hazard ratio (HR) 2.01, 95% Confidential interval (CI) 1.12–3.60, P = 0.019; group C: HR 3.00, 95% CI 1.34–6.72, P = 0.008]. Addition of mesentery spread to the N classification was significant risk factor for recurrence (mN2a: HR 2.01, 95% CI 1.07–3.78, P = 0.029; mN2b: HR 3.96, 95% CI 2.12–7.40, P < 0.01). Comparison of Harrell's C-index values was conducted, and the modified N staging risk was 0.6377, whereas the TNM N stage classification was 0.5869. Conclusion: Mesentery location of LNM was a risk factor and consideration of it might be beneficial for accurate prediction of CRC prognosis.
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