Comparison of lymph node staging system in gastric cancer using time-dependent ROC analysis with Harrell’s concordance index.

Abstract

12 Background: The aim this study was to clarify what the most informative pathologic lymph node staging system in gastric cancer is, by using time-dependent receiver operating characteristic (ROC) analysis with Harrell’s concordance (c) index. Methods: This study enrolled 2747 primary gastric cancer patients, without prior chemotherapy, who underwent R0 or R1 macroscopically curative resection. We calculated concordance indices of different 3 nodal staging systems (anatomical level based on JPN 13th edition vs. numbers of metastatic nodes based upon TNM 7th edition vs. ratio of metastatic nodes; derived from Yu’s definition {Yu et al. Br J Surg;1997,N0:0, N1;0-0.1, N2;0.1-0.25, N3;0.25-}) for survival. Results: (Anatomical level) Harrell’s c-index was 0.754 with 5-year survival rate of N0; 93%, N1; 73%, N2; 51%, N3; 19%. C-index without node-negative patients was 0.628. (Numbers of positive nodes) C-index was 0.767 with 5-year survival rate of N0; 93%, N1; 81%, N2; 68%, N3; 37%. C-index without node-negative patients was 0.669. (Ratio of nodal involvement) C-index was 0.770 with 5-year survival rate of N0; 93%, N1; 80%, N2; 63%, N3; 29%. C-index without node-negative patients was 0.691, which is significantly larger than those in anatomical level or numbers of positive nodes (p<0.001, p=0.014, respectively). (Comparison of Staging System) If combined pT category with ratio grading system without pStage IA, new staging system is the significantly most informative (c-index; 0.760) than JPN 13th (c-index; 0.735) or TNM 7th (c-index; 0.742) (p=0.009, p=0.023, respectively). Conclusions: Lymph node staging system based on the conception of ratio of metastatic nodes is the most informative staging system than those with anatomical location or numbers of metastatic nodes. These results suggested that in gastric cancer pathologic staging system in next TNM classification should include the ratio of metastatic nodes.