OBJECTIVESTo compare the prognostic value of three lymph node(N) staging systems, including the number of metastatic lymph nodes(pN), the metastatic lymph node ratio (Nr) and the log odds of positive lymph nodes (LODDS), in gastric cancer patients after radical resection.

METHODSClinical and pathological data of 1 796 patients who underwent gastric cancer radical resection with complete follow-up information from January 2000 to December 2010 at Sun Yat-sen University Cancer Center were retrospectively analyzed. For each patient, N stages were classified according to three lymph node staging systems (pN, Nr, and LODDS). The relationship between each N staging was examined. Survival was analyzed using the Cox's proportional hazard model, and discrimination of staging system was determined using the change value of Chi squared statistic (▹χ) from the log-likelihood test. A larger ▹χvalue indicates a better discriminatory ability. The homogeneity of 5-year overall survival across each pN stage within each Nr and LODDS stage was compared by using the log-rank test. The subgroup analysis was performed to evaluate whether each of the competing system was affected by the number of lymph nodes retrieved.

RESULTSThe mean number of lymph node examined and positive nodes in the entire cohort was 21.1±12.1 and 7.9±8.2,respectively. The median overall survival of all the patients was 45 months (95% CI: 42.6 to 47.4 months), and the 5-year survival rate was 55.0%(95% CI: 52.6% to 57.4%). The ▹χof Nr system was 198.546, which was higher than that of pN(191.255) and LODDS(196.557) system. Except for the pN3b stage, significant heterogeneity was found among patients of different Nr subcategories in 5-year overall survival rate (all P<0.05) within each pN stage. While there was no significant difference in overall survival when any of the Nr stages was stratified by pN stages(all P>0.05). Significant difference in survival among patients of different LODDS subcategories was also seen within each pN stage. But for the LODDS system, the survival rate was similar among patients of different pN subcategories (all P>0.05) apart from the LODDS3 stage. The hazard ratios of patients with insufficient lymph nodes examined (≤15) were higher than those with sufficient nodes examined (>15) when the pN classification was used (all P<0.05), whereas similar results were not found if the Nr or LODDS classification was applied.

CONCLUSIONCompared with the pN staging system, both the Nr and LODDS staging system, especially the former, have a higher degree of discrimination ability and robustness to predict the prognosis in patients with gastric cancer after radical resection.