Metastatic lymph node ratio is an independent prognostic factor in gastric cancer

The metastatic status of the regional lymph node is the most significant prognostic factor for gastric cancer. However, diverse prognoses are evident even among the same N classifications of the current tumor-node-metastasis system. The aim of this study is to evaluate the prognostic significance of the ratio of metastatic to examined lymph nodes (N ratio) for identifying a high-risk subgroup of patients with gastric cancer.

The postoperative survival of 264 consecutive patients with operable gastric cancer was analyzed with regard to its N ratio and current N classification. Survival was determined by the Kaplan-Meier method and differences were assessed by the log-rank test. Multivariate analysis was performed using the Cox proportional hazards model in forward stepwise regression.

The lymph node ratio was classified as follows N ratio 1, 1 to 10, N ratio 2, 11 to 25; and N ratio 3, >25. The 5-year survival rates stratified by N ratio were N ratio 1, 81%; N ratio 2, 49%; N ratio 3, 25%. The rates of survival were significantly different according to the N ratio in pN1 and pN2 classification of the UICC/TNM classification (p<0.05). Cox regression analysis revealed that N ratio was sensitive prognostic factor in these surgically treated patients, which were also significantly correlated with extent of lymph node dissection and pathologic tumor stage (p<0.05).

N ratio can be recommended as an applicable parameter for lymph node involvement of gastric cancer. It is a more effective and precise indicator for prognostic stratification of patients with lymph node positive gastric cancer than the current N classification of the tumor-node-metastasis system.