. 2011 Dec 7;103(24):1851–1858. doi: 10.1093/jnci/djr485

Table 4.

C-index from four Cox models to compare the predictive accuracy for overall survival using patient- and/or clinician-reported symptoms and P values for comparisons between models for pain, fatigue, vomiting, nausea, diarrhea, and constipation^*

Clinical symptom	C-index				P^¶_{model 2 vs model 3}	P^¶_{model 3 vs model 4}
Clinical symptom	Model 1^†	Model 2^‡	Model 3^§	Model 4^‖	P^¶_{model 2 vs model 3}	P^¶_{model 3 vs model 4}
Pain	.60	.62	.62	.63	.59	.44
Fatigue	.60	.66	.63	.67	<.001	<.001
Vomiting	.62	.64	.62	.64	.01	.01
Nausea	.62	.65	.62	.65	<.001	<.001
Diarrhea	.62	.62	.62	.62	.08	.52
Constipation	.60	.62	.61	.62	.03	.01

Four different Cox models were analyzed for each symptom, as described below. The C-index calculates the predictive accuracy from the Cox model to predict overall survival. (The C-index estimates the percentage in which the correct predictions derived from the Cox model and the observed survival order are in agreement, with C = 0.5 for a random model with no variables and C = 1 with a perfect order concordance.)

^†

Model 1 includes the sociodemographic and clinical variables alone.

^‡

Model 2 includes the sociodemographic and clinical variables and patient symptom rating.

^§

Model 3 includes the sociodemographic and clinical variables and clinician symptom rating.

^‖

Model 4 includes the sociodemographic and clinical variables and both patient and clinician symptom ratings.

^¶

P values are from two-sided tests. Each P value tests the hypothesis that the predictions from one Cox model, indicated by the C-index is more concordant with the observed outcome than predictions from the other Cox model, indicated by the C-index, within paired predictions. In this analysis, we compared model 2 vs model 3 and model 3 vs model 4.