Comment.

The article comments on the paper by Murray Aitkin, Nan Laird and Brian Francis which presents an analyses of survival of patients in the Stanford Heart Transplantation Program, published in the June 1983 issue of the "Journal of the American Statistical Association." The author congratulates Aitkin, Laird and Francis on a fine article that provides some new results on the fitting of the heart transplant data to various models. However, there is one important point that was not addressed in the article. This is the effect of competing risks of death for the transplanted patients. That is, the survival distribution and the influence of the covariates may differ depending on whether the patient dies from a rejected transplant or from other causes. The issue of competing risks has been addressed in previous analyses. In one analysis, those transplanted patients were considered who died from other causes as being censored, while the other estimated separate hazards and covariate parameters for the competing risks of death. This was accomplished by fitting an overall stochastic model with separate states for non-transplanted and transplanted patients as well as for death due to rejection of the transplant or to other causes.