Successful Peripheral Blood Stem Cell (PBSC) Mobilisation with G-CSF in Patients with Chronic Myeloid Leukaemia Achieving Complete Cytogenetic Remission with Imatinib.

The clinical studies have demonstrated the efficacy of Imatinib in the induction of hematological remission, cytogenetic remission (CCR) and molecular reduction of the bcl-abl transcript as shown by RT-qPCR. Unfortunately, the optimal long-term management of patients who achieve CCR after Imatinib is unknown. It is unclear that Imatinib alone will prove to be curative and initial responders may eventually lose Imatinib responsiveness. Therefore it may be prudent to collect autologous PBSC in CCR patients treated with Imatinib with low levels of detectable leukemia analyzed by molecular tests. We evaluated G-CSF mobilisation of PBSC in 18 patients who have achieved CCR with Imatinib. Our data demonstrated that the target CD34⁺ cell yields of ≥ 2.0x10⁶/kg was attained with G-CSF at the dose of 10 mg/kg/day in 4/8 (50%) patients during uninterrupted Imatinib therapy and in 8/10 (80%) when Imatinib was temporarily interrupted. Three patients (37%) in the first group and 7 patients (70%) in the second group achieved >1x10⁶/kg CD34⁺ cell yield per apheresis. Twelve patients were evaluated on PBSC for bcr-abl by RT-qPCR. Three patients were negative and in the other 9 patients, a median of 0.20 (range, 0.02–8.6) remained detectable. These data compared favourably with a median of 0.04 (range, 0.02 – 0.86) of all measurements taken before mobilisation. There was no impact of G-CSF mobilisation on the CML as measured by cytogenetic and serial blood bcr-abl levels. In conclusion, PBSC mobilisation with Imatinib and G-CSF in CCR patients is feasible, CD34⁺ cell yield is significantly better with temporary withheld of Imatinib, G-CSF did not preferentially mobilize leukemic progenitors and leukemic burden did not show significant change in the months following G-CSF mobilisation.