Figure 3. Construction of cox regression model. (A) The heatmap performed in R software on basis of risk score level and clinical characteristics (grade p=0.003). N stands for N classification in TNM system, and T stands for T classification in TNM system. (B) Survival analysis based on risk score. (C) The risk score distribution of differentiation grades. The y axis represent risk score level and x axis represent different grade (grade1 vs grade2, p=0.0002; grade1 vs grade3+4, p=0.0001). (D, E) Univariate cox regression and multivariate cox regression according to risk score and clinical characteristics. N stands for N classification in TNM system, and T stands for T classification in TNM system.