Abstract
BackgroundThe consensus is that a minimum of 12 lymph nodes should be analyzed at colectomy for colon cancer. However, right colon cancer and left colon cancer have different characteristics, and this threshold value for total number of lymph nodes retrieved may not be universally applicable.MethodsThe data of 63,243 patients with colon cancer treated between 2004 and 2012 were retrieved from the National Cancer Institute’s Surveillance, Epidemiology, and End Results database. Multivariate Cox regression analysis was used to determine the predictive value of total number of lymph nodes for survival after adjusting for lymph nodes ratio. The predictive value in left-sided colon cancer and right-sided colon cancer was compared. The optimal total number of lymph nodes cutoff value for prediction of overall survival was identified using the online tool Cutoff Finder. Survival of patients with high total number of lymph nodes (≥12) and low total number of lymph nodes (< 12) was compared by Kaplan–Meier analysis.ResultsAfter stratifying by lymph nodes ratio status, total number of lymph nodes≥12 remained an independent predictor of survival in the whole cohort and in right-sided colon cancer, but not in left-sided colon cancer. The optimal cutoff value for total number of lymph nodes was determined to be 11. Low total number of lymph nodes (< 11) was associated with significantly poorer survival after adjusting for lymph nodes ratio in all subgroups except in the subgroup with high lymph nodes ratio (0.5–1.0).ConclusionsPrevious reports of the prognostic significance of total number of lymph nodes on node-positive colon cancer were confounded by lymph nodes ratio. The 12-node standard for total number of lymph nodes may not be equally applicable in right-sided colon cancer and left-sided colon cancer.
Highlights
The consensus is that a minimum of 12 lymph nodes should be analyzed at colectomy for colon cancer
Right-sided colon cancer is more likely to belong to the consensus molecular subtype 2 (CMS2) and to show high frequency of DNA somatic copy number alterations (SCNA) and microsatellite stable/weak immune activation, which makes it relatively insensitive to immunotherapy [11]
The proportion of high total number of lymph nodes patients was higher in right-sided colon cancer than in left-sided colon cancer (79% vs. 68%; Table 1)
Summary
The consensus is that a minimum of 12 lymph nodes should be analyzed at colectomy for colon cancer. In patients with colon cancer’ survival is independently associated with the number of lymph nodes analyzed at the time of colectomy [1]. This is true in both nodepositive and node-negative disease, indicating that the benefit is not solely due to upstaging and administration. Wang et al found that the significance of the total number of lymph nodes as a quality-of-care measure in stage III colon cancer disappeared after adjusting for the effect of lymph nodes ratio [13]. They did not take tumor location into consideration. When a previous study has reported that between 1988 and 2011 there has been marked increase (from 20% to 80%) in the number of patients having ≥12 lymph nodes excised during colectomy for colon cancer [14]
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