Abstract
BACKGROUND
Imatinib mesylate administration has become standard treatment for patients with chronic myelogenous leukemia (CML). Although the safety profile of imatinib is favorable, Grade ≥ 3 neutropenia (according to the National Cancer Institute Common Toxicity Criteria) occurs in 35–45% of patients with CML in chronic phase who receive standard‐dose imatinib. Myelosuppression results in treatment interruptions, which may compromise responses to imatinib. The authors investigated the ability of granulocyte–colony‐stimulating factor (filgrastim) to reverse imatinib‐associated neutropenia, thereby allowing for more continuous imatinib administration.
METHODS
Thirteen patients with chronic‐phase CML and Grade ≥ 3, imatinib‐induced neutropenia were treated with filgrastim. Treatment with filgrastim was initiated after a median of 22 months from the start of imatinib. Eleven patients received filgrastim 5 μg/kg 1–3 times weekly, and 2 patients received filgrastim 5 μg/kg daily; doses were titrated to maintain an absolute neutrophil count (ANC) ≥ 10^9^/L.
RESULTS
Seven of 11 patients (64%) who began treatment with an ANC < 1.5 × 10^9^/L had responses (i.e., their ANC improved to ≥ 2 × 10^9^/L within 21 days); the other 4 patients experienced slower recovery but were able to continue receiving imatinib uninterrupted. Before filgrastim administration was initiated, patients did not receive imatinib (due to neutropenia‐related treatment interruptions) for an average of 21% of the total time since the start of imatinib. This figure decreased to 6% after the start of filgrastim treatment (P = 0.0008). Before filgrastim treatment was initiated, only one patient had achieved a major (partial) cytogenetic response. After the start of filgrastim treatment, five patients had major cytogenetic responses (including two complete responses).
CONCLUSIONS
The authors concluded that filgrastim may overcome imatinib‐associated neutropenia and allow improved delivery of imatinib. Some patients may experience improvements in their responses to therapy as a result. Cancer 2004. © 2004 American Cancer Society.