Covariance Analysis of Censored Survival Data

The use of regression models for making covariance adjustments in the comparsion of survival curves is illustrated by application to a clinical trial of maintenance therapy for childhood leukemia. Three models are considered: the log linear exponential (Glasser 1967); Cox's 1972 nonparametric generalization of this; and the linear exponential (Feigl and Zelen 1965). Age and white blood count at diagnosis are both shown to be important for prognosis; adjustment for the latter variable has marked effects on the treatment comparisons. Both advantages and disadvantages with the regression approach are noted.