Prognostic implication of metastatic lymph node ratio in node-positive rectal cancer

PURPOSE The aim of this study was to evaluate the prognostic significance of the ratio between metastatic and examined lymph nodes (LNs) in patients with stage III rectal cancer. METHODS A review was made of 175 (male, 98) patients with stage III rectal cancer of R0 resection. LN disease was stratified both by the American Joint Committee on Cancer/International Union Against Cancer nodal classification (pN) and by quartiles of the lymph node ratio (LNR). Disease-free survivals (DFS) were made using Kaplan-Meier curves and assessed by the log rank test and multivariate analysis was performed using the Cox proportional hazards model. RESULTS Patients ranged in age from 29 to 83 (median, 60) years with median follow-up of 47 months (range, 13 to 181 months). months. There was a significant correlation between the number of metastatic LNs and the LNR (r = 0.8681, P < 0.0001). Cut-off points of LNR quartiles best to separate patients with regard to 5-year DFS were between quartile 2 and 3, and between 3 and 4 (LNR1, 2, and 3); the 5-year DFS according to such stratification was 89.6%, 55.8%, and 18.2% in LNR1, 2, and 3, respectively (P < 0.0001). Cox model identified the LNR as the most significant independent prognostic covariate; LNR2 showed 3.6 times (95% confidence interval [CI], 1.682 to 7.584; P = 0.0009) and LNR3, 18.7 times (95% CI, 6.872 to 50.664; P < 0.0001) more risky than LNR1. CONCLUSION This study suggests that ratio-based LN staging, which reflects the number of LNs examined and the quality of LN dissection, is a simple and reliable system for prognostic LN stratification in patients with stage III rectal cancer.