Nonparametric estimation for the three-stage irreversible illness-death model

In this paper, we present new nonparametric estimators of the stage-occupat ion probabilities in the three-stage irreversible illness-death model. Thes e estimators use a fractional risk set and a reweighting approach and are v alid under stage-dependent censoring. Using a simulated data set, we compar e the behavior of our estimators with previously proposed estimators. We al so apply our estimators to data on time to Pneumocystis pneumonia and death obtained from an AIDS cohort study.