Table 3.

Characteristics of the measures implemented to evaluate the prediction ability of a model

Aspect	Measure	Characteristics
Discriminative ability	Kaplan-Meier curves for risk groups	Better with greater distance between the Kaplan-Meier curves for the low- and high risk groups
	C-index	Estimates the concordance probability, i.e. the probability that the score correctly orders two patients with respect to their survival time; higher values correspond to better prediction
	K-statistic	Alternative to the C-index; works only under the proportional hazards assumption
Calibration	Survival curves	Compares the observed survival function with the average predicted curve
	Calibration slope	Computes the regression coeffcient of the prognostic score as unique predictor; the best values are those close to 1; related to overfitting issues
Overall prediction	Prediction error curves	Presents the Brier score versus time; the closer the curves are to the X-axis, the better the prediction
	Integrated Brier score	Computes the area under the prediction error curves; the smaller is the value, the better the prediction