PROPORTIONAL EXCESS HAZARDS

Assume that the excess risk of an individual over a known background r ate can be well approximated by the proportional hazards model. Such m ight be the case for a cohort at risk of dying from causes that are in dependent of those that affect the general population. We propose esti mators for both the regression parameters and the nonparametric baseli ne hazard function. The estimators are shown to be consistent, asympto tically normal and efficient. Analogues of the Wald, score and likelih ood ratio test are provided,The relevance of the asymptotic results to samples of sizes 500 and 100 is illustrated by simulation. The model is used to estimate the prognostic significance of stage and histology in adults with non-Hodgkin's lymphoma.