Development and internal validation of the nomogram
NRI
REGRESSION
Finally, ten variables screened by multivariate Cox regression were applied to develop the nomogram for predicting the 1-, 3-, and 5-year CSS in GNEC patients (Fig. 
A predictive nomogram for postoperative GNEC patientsThe C-indexes were 0.792 (95% CI: 0.770–0.813) and 0.782 (95% CI: 0.749–0.815), respectively, for the training and internal validation groups. The DCA, calibration, and receiver operating characteristic (ROC) curves were displayed in Figs. 
ROC of the nomogram for 1-, 3-, and 5-year CSS prediction. 
Calibration curves of 1-, 3- and 5-year CSS. 
Decision curve analysis of 1-, 3- and 5-year CSS. The projected CSS rates at 1-, 3-, and 5-year were highly consistent with the results as shown by the calibration curves (Fig. 
 C-index analysis. 
NRI and IDI of the nomogram and AJCC staging criteria alone in CSS prediction for postoperative GNEC patientsThe outcomes provided compelling evidence that the nomogram outperformed the AJCC stage system regarding application value and predictive ability.