Imatinib plus Granulocyte Colony-Stimulating Factor in Chronic Myeloid Leukemia Patients Who Have Achieved Partial or Complete Cytogenetic Response while on Imatinib

BACKGROUND: The BCR/ABL tyrosine kinase inhibitor imatinib is highly effective in the treatment of chronic myeloid leukemia (CML) but fails to eliminate all leukemia cells. In this study, we investigated whether the addition of granulocyte colony-stimulating factor (G-CSF) could reduce the level of residual disease in patients with Ph-positive CML who appeared to have achieved a suboptimal response to imatinib alone. METHODS: Eleven patients with CML who had achieved ≥35% Ph-negativity on imatinib were enrolled. The starting dose of imatinib was 400 mg or 600 mg orally daily, and of G-CSF 5 µg/kg s.c. daily. The administration of G-CSF was postponed or interrupted in the event of leukocytosis (≥30 ×10(9) leukocytes/l) until the white blood cell count fell below 20 × 10(9)/l. Efficacy was assessed by serial monitoring of blood levels of BCR-ABL transcripts. RESULTS: Of 11 evaluable patients, 9 had an appreciable decline in BCR-ABL transcript levels; in 7 cases the reduction was greater than 1 log. CONCLUSIONS: We conclude that the addition of G-CSF should be considered for patients on imatinib who fail to obtain optimal response to imatinib alone and that this approach deserves further evaluation as frontline therapy for newly diagnosed CML.