OBJECTIVE: To analyze the prognostic implications of the lymph node ratio (LNR) in curative resected rectal cancer.

SUMMARY BACKGROUND DATA: It has been proposed that the LNR has a high prognostic impact in colorectal cancer, but the lymph node ratio has not been evaluated exclusively for rectal cancer in a large national cohort study.

METHODS: All 6793 patients in Denmark diagnosed with stage I to III adenocarcinoma of the rectum, and so treated in the period from 2003 to 2011, were included in the analysis. The cohort was divided into two groups according to whether or not neo-adjuvant treatment had been given.

RESULTS: In a multivariate analysis the pN status, ypN status and lymph node yield were found to be independent prognostic factors for overall survival, irrespective of neo-adjuvant therapy. The LNR was also found to be a significant prognostic factor with a Hazard Ratio ranging from 1.154 (95% CI: 0.930-1.432) (LNR: 0.01-0.08) to 2.974 (95% CI: 2.452-3.606) (LNR > 0.5) in the group of patients who had surgery to begin with and from 1.381 (95% CI: 0.891-2.139) (LNR: 0.01-0.08) to 2.915 (95% CI: 2.244-3.787) (LNR > 0.5) in the group of patients who had neo-adjuvant treatment.

CONCLUSIONS: The LNR reflects the influence on survival from N-status and the lymph node yield and since LNR was shown to be a significant prognostic predictor for overall survival in patients with curatively resected stage III rectal cancer irrespective of neo-adjuvant therapy we recommend that the introduction of LNR should be considered for rectal cancer in a revised TNM classification.