Adequate lymph node examination is essential to ensure the prognostic value of the lymph node ratio in patients with stage III colorectal cancer

Purpose. This study aimed to assess the prognostic value of the lymph node ratio (LNR), estimated by dividing the number of positive lymph nodes (LNs) by the number of LNs examined, for stage III colorectal cancer in comparison to the new tumor, nodes, and metastasis (TNM) system, and to evaluate the relationship between the number of LNs examined and the prognostic value of the LNR. Methods. We retrospectively reviewed the clinicopathological data of a cohort of 266 patients with stage III colorectal cancer. We assessed the impact of LNR on the prediction of cancer recurrence in comparison to the TNM system, as well as the prognostic value of LNR in patients with a low LN count. Results. In multivariate analysis, the LNR was found to be an independent risk factor of cancer recurrence. The application of the LNR, in addition to the new TNM system, was more predictive of survival than the TNM system alone. A prognostic separation by LNR was observed in patients who had an adequate number of LNs examined, but not in patients with a low LN count. Conclusions. A stronger prognostic separation can be obtained by using the LNR together with the new TNM system. Adequate lymph node examination is important to ensure the prognostic value of LNR in patients with stage III colorectal cancer.