Hematopoietic growth factors as adjuncts to the treatment of acute myeloid leukemia.

A number of randomized trials have recently been completed evaluating the effect of hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor or granulocyte colony-stimulating factor) as adjuncts to the treatment of patients with acute myeloid leukemia. Most studies used the growth factors to decrease the duration of neutropenia with the hope of reducing infectious morbidity and mortality. The results of these trials are generally quite consistent. Virtually all trials showed a modest reduction in the duration of severe neutropenia with a variable effect on the incidence of severe infections, antibiotic usage, and the duration of hospitalization. There was no consistent benefit in terms of improvements in complete response rate, complete response duration, or overall survival. However, it is important that there does not appear to be an increase in the incidence of drug-resistant leukemia in trials in which the growth factor was begun after completion of the chemotherapy. Other trials administered growth factors either before or simultaneous with the chemotherapy in an attempt to enhance chemosensitivity and decrease drug resistance. None of these trials, whether conducted as part of initial induction therapy or in relapse, showed improvements in response rate or survival. Lastly, some anecdotal reports have suggested that occasional patients who receive growth factors as the only therapy for overt leukemia can achieve remission, possibly through a differentiating effect of the growth factor. However, there are very few such reports, and growth factor use in this situation is potentially dangerous and should be performed only in the context of a clinical trial. In summary, there appears to be no role at this time for priming of leukemia cells by growth factors to enhance the effect of chemotherapy, and more in vitro studies should be performed before further clinical trials of this approach. It is clear that growth factors administered after induction and possibly consolidation chemotherapy can shorten the duration of neutropenia, without a significant effect on treatment outcome. It is as yet unclear whether the use of growth factors in this fashion is cost effective.