Data are expressed as the mean ± SEM, and error bars in the figures refer to SEM, median, and interquartile range (IQR). The analysis of association between variables was conducted using the Mann–Whitney U‐test, Student t‐test, chi‐square test, or one‐way ANOVA test when appropriate. Univariate analysis was based on the Kaplan–Meier method using the log‐rank test. Cox proportional hazards regression was used for multivariate analyses. SPSS software (IBM, Armonk, NY, USA) and Graph Pad Prism 6.0 (Graph Pad Software Inc, San Diego, CA, USA) were applied for data analyses. Statistical tests were two‐sided, with p < 0.05 considered significant.