Prognostic value of preoperative carcinoembryonic antigen/tumor size in rectal cancer

Figure 6 Proportional hazards assumption test for disease-free survival by plotting the Schoenfeld residuals against time in the training cohort (A, C, and E) and the validation cohort (B, D, and F). The X-axis represents the survival time, while the Beta values referring to TNM stage, lymphovascular invasion, and carcinoembryonic antigen/tumor size are shown on the Y-axis. The constant mean of residuals across time confirms that the proportional hazard assumption holds for these covariate with all of the P-values > 0.05. CEA: Carcinoembryonic antigen.