Construction of prediction model
We constructed receiver operating characteristic (ROC) curves to determine the optional cutoff values of all variables based on samples in the training cohort. The values of maximum joint sensitivity and specificity on the ROC plot were defined as the recommended cutoff value. Continuous variables were converted into dichotomous variables by their optimal cutoff. Both univariate and multivariate analyses were used to analyze variables affecting RFS, and variables significantly associated with RFS were included in the multivariate analysis. A nomogram was created using variables significantly associated with RFS in the multivariate analysis.