When a new product with huge clinical potential explodes on the scene, the hope is that the benefits far outweigh the risks in long-term administration. After 10 years of clinical use,
granulocyte colony-stimulating factor (
G-CSF) has lived up to that promise so far. In the context of
severe chronic neutropenia, more than 90% of patients have reaped big benefits in terms of improved quality of life and less
infection,
inflammation,
antibiotic use, and hospitalization as well as oropharyngeal
ulcers. With long-term use, toxic and adverse events have been catalogued but in general are not clinically troublesome and, aside from occasional adjustment of scheduling and dosing, seldom necessitate stopping
therapy. Currently, the topic of intense focus is the phenomenon of malignant myeloid transformation in patients with
congenital neutropenia who are receiving
G-CSF. Data from the
Severe Chronic Neutropenia International Registry have identified 23 of 249 patients with
congenital neutropenia who have developed myelodysplasia or
acute myelogenous leukemia (MDS/AML) giving a crude rate of about 9% with an average follow-up of 4.5 years. No cases of MDS/AML have occurred in 257 patients with cyclic or idiopathic
neutropenia. A critical analysis of the incidence of transformation year by year showed a fairly uniform hazard rate of less than 2% per year, and the risk of MDS/AML after 5 to 6 years of
therapy did not appear to be greater than during the first year of
therapy. The transformation risk in the congenital cohort must also be viewed in the context of published reports of spontaneous myelodysplasia or
acute myelogenous leukemia occurring in these patients in the pre-
G-CSF era. Thus, the role of
G-CSF in malignant conversion is still not clear and requires long-term vigilance and research.
G-CSF is still deemed specific
therapy for
severe chronic neutropenia with a high margin of safety and should be the initial treatment for this family of disorders.