Validation of nomograms and performance evaluation
The nomograms were subjected to internal validation in the validation cohort, where the concordance index (C-index) was calculated. In the training cohort, the C-index for OS was 0.717 (95% CI: 0.701-0.732), and for CSS, it was 0.747 (95% CI: 0.730-0.764). The C-index for the validation cohort was also calculated for both OS and CSS, which were found to be 0.708 (95% CI: 0.682-0.733) and 0.740 (95% CI: 0.715-0.766), respectively. The C-index values for the validation cohort were found to be moderate, indicating a reasonable degree of accuracy for the nomograms. To assess the predictive performance of our nomograms, we utilized two evaluation methods: calibration curves and time-dependent ROC curves. The calibration curves, as depicted in Calibration curves of the nomograms to predict OS and CSS at 1-, 3-, and 5-year for elderly patients with GBC. Time-dependent ROC curves to predict OS and CSS at 1-, 3-, and 5-year for elderly patients with GBC. 