Hematopoietic growth factors.

Over the past ten years, the availability of pharmacologic quantities of hematopoietic growth factors has opened many avenues of study in basic science and clinical investigation. Numerous studies performed to date have demonstrated significant benefits from the use of these cytokines. The side effect profiles, particularly for "later acting" growth factors, indicate that they are generally well tolerated by most patients. The table summarizes the potential indications for hematopoietic growth factor use as discussed in this article, as justified by current evidence of benefit, harm, and cost effectiveness resulting from their use in various clinical settings. It has been clearly demonstrated in standard-dose chemotherapy regimens that these agents shorten the duration of myelosuppression, reduce the incidence of significant infection, can shorten hospital stay, and reduce antibiotic use for most patients, although the cost/benefit ratio for growth factors such as G-CSF makes this a cost-effective approach only for regimens with a high (40 percent or more) incidence of febrile neutropenia. Limited indirect evidence supports the use of growth factors in patients with a prior episode of fever and neutropenia. The suppressive approach to growth factor use could potentially benefit patients with documented infection or clinical deterioration, but it has not otherwise been shown to be a particularly effective or cost-effective approach. Administration of hematopoietic growth factors has been instrumental in facilitating both autologous and allogeneic peripheral progenitor cell mobilization and techniques such as ex vivo expansion. There is an increasing body of data supporting the use of high-dose chemotherapy regimens with progenitor cell rescue for a number of malignancies and limited data supporting the benefits of maintaining dose-intensity for certain malignancies in standard-dose settings. Although of continuing concern, clinically significant evidence of disease stimulation and recurrence has not been unequivocally demonstrated in studies to date. A comprehensive set of evidence-based guidelines has recently been published by the American Society of Clinical Oncology. As often is the case, current studies have perhaps generated more questions than answers. Future investigation will undoubtedly focus on use of hematopoietic growth factors in conjunction with other techniques, such as outpatient-based treatment of febrile neutropenia, CD34-positive stem cell selection in autologous transplantation, selective manipulation of T-cell subsets (to decrease the incidence of severe graft-versus-host disease) in allogeneic transplantation, and high-dose therapy with stem cell transplantation.