Granulocyte colony-stimulating factor reverses cytopenia and may permit cytogenetic responses in patients with chronic myeloid leukemia treated with imatinib mesylate

Imatinib mesylate induces major or complete cytogenetic responses in the majority of patients with chronic myeloid leukemia (CML) in chronic phase. However, 15-40% of patients develop neutropenia and/or thrombocytopenia that makes it necessary to reduce the dosage or to interrupt treatment. Patients with recurrent cytopenias may be less likely to obtain cytogenetic responses. We speculated that low doses of granulocyte colony-stimulating factor (G-CSF) in conjunction with imatinib might offer clinical benefit. Eleven patients with CML in chronic (n=9) or accelerated (n=2) phase who could not tolerate 300 mg/day and had no cytogenetic response after 6 months of imatinib treatment received G-CSF in combination with imatinib. Ten of the 11 patients could then tolerate doses of imatinib equal to or greater than 300 mg/day and 7 patients achieved major (n=6) or complete (n=1) cytogenetic responses. We conclude that G-CSF reverses the hematologic toxicity of imatinib and may thereby increase the proportion of cytogenetic responses.