*2.7. Statistical Analysis*

Univariate analysis was performed using the *t*-test (or Wilcoxon rank sum test) and the chi-square test (or Fisher's exact test) for continuous and categorical variables, respectively. The correlation between methylation levels of CpGs in the *RUNX1* gene was analyzed using Spearman's rank correlation coefficient. The effect of reduced RUNX1 expression on survival was estimated using the Kaplan–Meier survival curves, and the difference between the survival curves of any two groups was evaluated by the log-rank test. Cox proportional hazards analysis was conducted to estimate the hazard ratios of reduced RUNX1 expression for survival after controlling for potential confounding factors. Statistical analysis was conducted using R software version 3.3.3. (R Foundation for Statistical Computing, Vienna, Austria).
