2.3. Statistical analysis
REGRESSION
Categorical variables are presented as frequencies and rates and were tested using the chi-square test. Univariate and multivariate Cox proportional hazards models were used to select independent prognostic factors for OS, and nomogram models were constructed to predict the OS at 6, 12, and 24 months. The prognostic models were internally validated using a cohort of 711 patients from the SEER database. Parameters for Cox proportional hazards regression analysis included hazard ratios and the corresponding 95% confidence intervals. The receiver operating characteristic curve (ROC) was used to hire the discrimination power of the current prediction model, and a larger area under the curve (AUC) ROC indicated a better model. Calibration plots were used for visual comparison of the nomogram-predicted prognosis with the actual prognosis. Decision curve analysis (DCA) was performed to assess the clinical validity of the predictive model. Statistical significance was set at 2-sided 