Nomogram evaluation
To evaluate the discriminative ability, we constructed a receiver operating characteristic (ROC) curve. The nomogram discrimination efficacy was assessed by concordance index (C-index) and the area under the ROC curve (AUC). They basically ranged from 0.5 (random prediction) to 1.0 (excellent prediction). In general, a value greater than 0.7 indicated that the performance of model was good with moderate prediction capacity [Finally, we used the β-coefficients derived from the final Cox model to weight individual factors and then summed all of their contribution to generate raw prognostic scores. To normalize these subsequent scores to a range between 0 and 5, we employed the following equation: (5–0) × (raw prognostic score – min_score)/(max_score – min_score) + 0 [