RSURV: a function to perform relative survival analysis with S-PLUS or R

Relative survival is a method used to estimate net survival using the expected mortality in the general population. This method is frequently used in cancer registries, more particularly with the Esteve et al. regressive proportional hazards model. Recently, extensions of this model have been developed to account for time-dependent covariate and for time-dependent hazards using B-spline functions. We propose a function, RSurv, to take into account these extensions. Written in the R/S language this function has the same structure of the standard Cox function coxph of R and S-PLUS software with the goal to homogenise survival functions and to take advantages of the power of R and S-PLUS software. We also propose a function, plot.RSurv, for plotting relative survival curves and time-dependent hazards ratio. The usage of these functions is exemplified by a study of a breast cancer hospital-based data set.