Statistical analysis
We used R software to randomly divide the cohort into a training set and a validation set in the ratio of 7:3, and the chi-squared test was performed to check the differences in the categorical variables between the two groups. We used the receiver operating characteristic (ROC) curve to evaluate discriminative ability and calibration plots to evaluate calibrating ability of the nomograms. Additionally, decision curve analysis (DCA) was used to quantify the clinical benefit of the cN-based nomograms. 