Upper and lower time limits in the decision to recommend marrow transplantation for patients with chronic myelogenous...

Long-term survival of patients with chronic myelogenous leukaemia (CML) requires marrow transplantation from a histocompatible donor. The optimal timing of the transplant is difficult to determine because of the high peritransplant mortality of 20-35% and the existence of a group of patients who can have the disease controlled by drug treatment for prolonged periods. We have developed a mathematical model implemented with a computer program which calculates lower and upper time limits for the timing of marrow transplantation. The lower time limit for transplantation is derived from the loss of life expectancy with delay, and the upper time limit is calculated by comparing the transplant survival probability with the probability of surviving an additional year without a transplant. Thus, an objective basis is provided for bracketing the most appropriate time for transplantation. This analysis suggests that the decision to transplant can be postponed in some patients for periods longer than may generally be recommended.