Predictive performance of the nomograms
The predictive performance of the traditional TNM staging system and our nomogram were examined. The traditional TNM staging system showed unsatisfied discriminative ability (training cohort: C index, 0.545; 95% CI, 0.508–0.582; internal validation cohort: C index, 0.517; 95% CI, 0.462–0.572; external validation cohort: C index, 0.602; 95% CI, 0.571–0.633). The C indices of the nomogram for OS estimates were 0.671 (95% CI, 0.637–0.705),0.632 (95% CI, 0.581–0.683), and 0.645 (95% CI, 0.617–0.673) in the training cohorts, internal validation cohorts, and external validation cohort, which demonstrated a good level of discriminative ability. As the calibration curves showed, there was an excellent agreement between the predicted OS by the nomogram and the actual OS probabilities we observed in the training cohorts, internal validation cohorts, and external validation cohort (see Fig. The calibration plots (