Hematopoietic progenitor cell collection in patients with chronic myelogenous leukemia in complete cytogenetic remission after imatinib mesylate therapy

The introduction of BCRABL tyrosine kinase inhibitors such as imatinib has changed the treatment of chronic myelogenous leukemia (CML). More than 75 of patients achieve complete cytogenetic remission (CCR) after treatment with imatinib, which provides an opportunity to collect minimally involved hematopoietic progenitor stem cell (HPC) products. In order to assess the feasibility of HPC collection in patients with CML, we prospectively enrolled 24 patients who achieved CCR on therapy with imatinib. Two patients could not undergo HPC collection because of coagulopathy. A CD34 cell yield of ≥2.0×10⁶/kg body weight was obtained in 16/22 (73) patients. Patients who stopped imatinib for at least 3 weeks prior to HPC collection had significantly higher CD34 cell yields (median: 6.52×10⁶/kg body weight) when compared with patients who continued imatinib through the collection (median: 3.74×10⁶/kg body weight). Mobilization with granulocyte colony-stimulating factor (G-CSF) did not increase the levels of BCRABL transcript. With a mean follow-up of 46 months, all patients but one were in CCR. In conclusion, a significant number of CD34 cells can be safely collected in patients with CML who are on imatinib therapy, but CD34 cell yields improve when imatinib is temporarily withheld.