highly significantP =0.0001
Cox multivariate regression model (IS and TNM staging) showed that IS has a highly significant correlation with OS (HR: 2.70; P =0.0001) and DFS (HR: 2.10; P =0.0008) compared to TNM staging system (HR: 1.92; P =0.057 for OS and HR: 1.95; P =0.039 for DFS) ( Table 4 ).