Abstract
Despite the adequacy of nodal evaluation was gradually improved for colon cancer, the disparity in nodal examination for right colon cancer (RCC) and left colon cancer (LCC) still begs the question of whether 12 nodes is an appropriate threshold for both RCC and LCC. From Surveillance, Epidemiology, and End-Results (SEER) database, we identified 53897 RCC patients and 11822 LCC patients. Compared with LCC patients, RCC patients examined more lymph nodes (18.7 vs 16.3), and more likely to examine ≥12 nodes (P<0.001), whereas RCC patients showed lower rates of node positivity (P<0.001). To balance the nodal disparity between RCC and LCC, we revised the 12-node measure based on different tumor locations. With the X-tile, we determined 15 as the optimal node number for RCC and 11 for LCC. To validate the availability of this revised nodal evaluation, the 5-year cancer specific survival (CSS) was calculated according to the optimal node number in RCC and LCC patients, Cox's regression model were used to further assess the prognostic value of this revised nodal evaluation. The results showed that 5-year CSSs were significantly improved for RCC patients with ≥15 lymph nodes, and also for LCC patients with ≥11 lymph nodes (P<0.001). This revised nodal evaluation could also improve the rate of nodal positivity and long-term survival in both RCC and LCC patients compared with 12-node measure. Therefore, the lymph node examination should be discriminately evaluated for RCC and LCC, instead of using 12-node measure to colon cancer as a whole.
Highlights
The presence of lymph node metastasis contributes to adverse prognostic implications for colon cancer patients
From the SEER database, we totally identified 65719 colon cancer patients including 53897 right colon cancer (RCC) patients and 11822 left colon cancer (LCC) patients
The number of lymph nodes evaluated for colon cancer has markedly increased in the past 2 decades [15], differences in nodal evaluation between RCC and LCC were continue to exist over time
Summary
The presence of lymph node metastasis contributes to adverse prognostic implications for colon cancer patients. Accumulating evidences have demonstrated that increasing number of lymph nodes examined for colon cancer contributed to the improvement of disease-free and overall survival [1,2,3,4,5]. The mechanisms underlying the potential association between lymph node count and survival outcomes remain unclear. Some studies have demonstrated that a greater host immune response [7], or other underlying molecular/ biological characteristics of tumor, may play a role among patients with a larger lymph node count [6]. [4, 8,9,10] Based on these studies, The American Society of Clinical Oncology (ASCO) and www.impactjournals.com/oncotarget the National Comprehensive Cancer Network (NCCN) guideline advocate that 12 regional lymph nodes should be the necessary minimum number for quality evaluation of colon cancer resection. It may be controversial that the 12node measure was applied in both RCC and LCC without consideration of different tumor locations
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