Long Term Outcomes for Patients with Cyclic Neutropenia Treated with Granulocyte Colony-Stimulating Factor (G-CSF)

Cyclic neutropenia (CyN) is a rare hematological condition with neutrophil counts decreasing to <0.2 x 10⁹/L, usually at 21 day intervals, accompanied by fever, mouth ulcers and the risk of severe sepsis during the neutropenic periods. Twenty-six years ago we reported results of treating six patients with CyN on G-CSF (N Engl J Med. 1989;320: 1306-1311). We have now followed these patients and many other CyN on G-CSF for up to 28 years through the Severe Chronic Neutropenia International Registry (SCNIR).

The original six patients (2 male, 4 female, ages 8.8 to 65) are all living, now ages 36 to 92 years. All of the original six had documented fever and recurring infections prior to treatment (i.e. mouth ulcers, gingivitis, lymphadenopathy, cellulitis, abscesses, pharyngitis, otitis, and pneumonia). Five were found to have mutations in ELANE after the discovery of mutations in this gene as the cause for CyN. The sixth patient, in retrospect, probably more appropriately should have be given the diagnosis of severe idiopathic neutropenia, is now age 92, off G-CSF and residing at home with skilled nursing care. The other five have maintained good health on G-CSF treatment and are now employed as teachers, working in a business, or retired. None have developed notable infections, hematological or other sequelae except for one patient with decreased bone density and one patient with idiopathic thrombocytopenia purpura (ITP) responding to splenectomy. In aggregate these six patients have received approximately 6.6 grams of G-CSF over 143 patient-years (median dose of G-CSF per patient per year is 0.035 gm, range 0.018 to 0.075 gm, treatment period: 7-28 years).

Our broader experience with 308 patients with the diagnosis of CyN based on serial blood counts and/or genotyping and treated with G-CSF is similar to these original six patients. However, we are aware of at least 40 cases of severe sepsis and 17 deaths in patients with CyN not on G-CSF. We are not aware of any such severe infections in CyN patients consistently receiving G-CSF (i.e. at least two or three times per week). We have recorded one case on chronic myeloid leukemia in a CyN patient never on G-CSF. For patients receiving G-CSF we have recorded one case of non-Hodgkin's lymphoma, one case of AML in patient with probable CyN having 2 ELANE mutations and a secondary CSF3R mutation, and one case of AML after chronic immunosuppressive therapy with cyclophosphamide.

Conclusion: Observations in 308 patients for 2993 years demonstrate that G-CSF is a very beneficial treatment for patients with CyN. There is good evidence that this treatment prevents severe infections and death from infections and there is a very low risk myeloid malignancies, and specifically conversion to MDS or AML.