Purpose: To investigate the prognostic impact of lymph node ratio (LNR) on survival in the patients with Stage III rectal cancer.
Methods and materials: We retrospectively reviewed the data of 421 consecutive patients who underwent total mesorectal excision followed by chemoradiotherapy for rectal cancer from 1996 to 2006. The 232 patients with positive lymph nodes (LNs) were divided into four groups according to LNR quartiles: LNR <or=0.1 (n = 69), <or=0.2 (n = 49), <or=0.4 (n = 54), and >0.4 (n = 60). The association between LNR and survival was evaluated by the Kaplan-Meier method and multivariate analysis with covariates of prognostic significance in univariate analysis.
Results: The median numbers of examined and positive LNs were 17 and 3, respectively, and the median LNR was 0.20 (range, 0.03-1). There was a strong correlation between the number of positive LNs and LNR (r = 0.724, p < 0.001). After a median follow-up of 53 months (range, 9-138 months), the actuarial overall survival and disease-free survival rates at 5 years were 69% and 56%, respectively. The 5-year survival rate decreased as LNR increased (<or=0.1, 89%; <or=0.2, 67%; <or=0.4, 64%; >0.4, 50%; p < 0.001). Lymph node ratio was also a significant prognostic factor on Cox regression analysis (<or=0.1, hazard ratio [HR] = 1; <or=0.2, HR = 1.3, p = 0.623; <or=0.4, HR = 2.4, p = 0.047; >0.4, HR = 3.7, p = 0.005). Lymph node ratio had a prognostic effect on overall survival in subgroups of patients with N1 (p = 0.032) and N2 (p = 0.034) tumors.
Conclusion: Lymph node ratio was the most significant predictor of survival in the patients with Stage III rectal cancer who had undergone postoperative chemoradiation.