Peripheral blood progenitor cell collection in chronic myeloid leukemia patients with complete cytogenetic response after treatment with imatinib mesylate

BACKGROUND: Imatinib mesylate (IM) was introduced in chronic myeloid leukemia (CML) treatment in the late 1990s and substantially changed the therapeutic approach to the disease, by inducing complete cytogenetic response (CCR) in approximately 60 percent of cases. Nevertheless, some concerns exist about the duration of response to treatment and the onset of resistance to IM. STUDY DESIGN AND METHODS: Twenty-five chronic-phase CML patients in stable CCR (>6 months) treated for at least 1 year with IM at the standard dose (400 mg/ day) were mobilized with recombinant human granulocyte-colony-stimulating factor (Filgrastim) at 10 μg per kg for 4 to 6 days, with the aim of collecting at least 2 × 10⁶ CD34+ cells per kg. Standard cytogenetic analysis and first-round and/or nested polymerase chain reaction were performed in basal and postmobilization samples to examine the presence of bcr-abl transcripts. RESULTS: CD34+ cells collection was successful in 16 patients, yielding a median of 3.01 × 10⁶± 1.09 × 10⁶ CD34+ cells per kg at the first attempt, and in 4 of the 9 remaining patients who were remobilized after a temporary withdrawal of IM, yielding a median of 2.65 × 10⁶ ± 0.7 × 10 ⁶ CD34+ cells per kg, with an overall 80 percent success rate. No correlation between mobilization and duration of the disease, length of IM treatment, or previous interferon-α and/or hydroxyurea treatment was found. CONCLUSIONS: Autologous CD34+ cells may be mobilized and collected in most CML patients who achieve CCR after IM treatment, with a view to possible use in the event that resistance to IM occurs in patients not eligible for allogeneic peripheral blood progenitor cell transplantation or those lacking an HLA-matched donor.