title: Use of the concordance index for predictors of censored survival data.
abstract: The concordance index is often used to measure how well a biomarker predicts the time to an event. Estimators of the concordance index for predictors of right-censored data are reviewed, including those based on censored pairs, inverse probability weighting and a proportional-hazards model. Predictive and prognostic biomarkers often lose strength with time, and in this case the aforementioned statistics depend on the length of follow up. A semi-parametric estimator of the concordance index is developed that accommodates converging hazards through a single parameter in a Pareto model. Concordance index estimators are assessed through simulations, which demonstrate substantial bias of classical censored-pairs and proportional-hazards model estimators. Prognostic biomarkers in a cohort of women diagnosed with breast cancer are evaluated using new and classical estimators of the concordance index.
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, UK.
authors.forename: Adam R
authors.initials: AR
authors.lastname: Brentnall
authors.affiliation: Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Cuzick
mesh_terms: D000465:Algorithms; D015982:Bias; D015415:Biomarkers / Q000032:analysis; D006801:Humans; D016016:Proportional Hazards Models; D016019:Survival Analysis
chemical_list: D015415:Biomarkers
keywords: Biomarkers; C-index; Pareto model; discrimination; proportional-hazards model; survival analysis