Impact of number of retrieved lymph nodes and lymph node ratio on the prognosis in patients with stage Ⅱ and Ⅲ colorectal cancer

Objective To discuss the impact of number of retrieved lymph nodes and lymph node ratio (LNR) on the prognosis in patients with stage Ⅱ and Ⅲ colorectal cancer.Methods Clinicopathological data of 507 patients with stage Ⅱ and Ⅲ colorectal cancer were analyzed retrospectively. Follow-up was available in all the patients. Results The total number of retrieved lymph nodes was 5801, of which 1122 had metastasis. There was a positive correlation between metastatic lymph nodes and retrieved lymph nodes (r=0. 171, P＜0.01). In stage Ⅱ colorectal cancer there was a significant difference in 5-year survival rate between patients with more than 12 lymph nodes retrieved and those with less than 12 lymph nodes retrieved (P＜0.01). LNR also affected the 5-year survival rate of patients with stage Ⅱ and Ⅲ colorectal cancer (P＜0.05). In patients with similar LNR, the 5-year survival rate differed significantly among different regions of lymph node metastasis(P＜0.05). LNR influenced the prognosis independent of the number of lymph nodes retrieved. Conclusions The number of retrieved lymph nodes is a prognostic factor for stage Ⅱ and Ⅲ colorectal cancer. More than 12 lymph nodes should be retrieved for better staging and prognosis. LNR is also a prognostic factor in stage Ⅱ and Ⅲ colorectal cancer. Regions of lymph nodes metastasis should be considered when evaluating the prognosis of patients using LNR.