Imatinib Mesilate (Glivec) is able to induce a high rate of Complete Cytogenetic Response (CCyR) with low treatment-related toxicity. The long-term duration of this Ph-negative status is, however, still undefined. Therefore, some groups (

Drummond et al, Br J Haematol 123:479, 2003
;
Hui et al, Leukemia 17:821,2003
) decided to mobilize and to collect Ph-negative PBSCs in patients reaching CCyR with Glivec. In our experience we studied 12 Ph-negative, FISH-negative patients, median age 50 yrs (26–61). Three of them were also PCR-negative, being the minimal residual disease assessed using RT-PCR. All patients received Imatinib Mesilate at the daily dose of 400 mg. The median duration of treatment with Glivec was 25 months (range 11–35). Eight of 12 pts (67%) were pre-treated with α-interferon (α-IFN) for a median time of 9.5 months (range 3–54). The median duration of CML was 39 months (range: 21–152).

We discontinued Imatinib four days (range 3–5) before starting rHu-G-CSF as single agent (5–10 μg/Kg/day), which was maintained until WBC < 50x109/L. Failure of mobilization was defined as CD34+ circulating cells < 10/m L. The collection started after a median of 6 days (range 4 –10), when CD34+ cells were > 10/μ L. Eleven of 12 pts (92%) reached the threshold of 10/μ L and started harvesting. The single patient failing collection had been pretreated with IFN and was PCR negative at the time of mobilization. The remaining 11 reached the target of 2.5 x106 CD34+ cells/Kg with a median of two apheresis (range 1–3). The median harvest was 3.14 CD34+ x 106/Kg (range 2.56–4.55). Conventional cytogenetic analysis, RT-PCR and coltural tests were performed in all apheretic samples. All the 11 mobilized patients obtained a Ph-negative harvest, which was also PCR negative in 4/11 (36%).

In our experience adequate yields of PBSCs were collected with rHu-G-CSF alone in 11/12 patients achieving CCyR with Glivec, as well as in the majority of those previously treated with α-IFN (7/8).

Results of harvesting after rHu-G-CSF alone in 11 CML patients achieving CCyR after Imatinib Mesilate

PatientN. ApheresisCD34+ x 10^6/kgRT-PCR
T.M 4.55 pos. 
O.I 3.34 neg. 
V.E. 3.33 neg. 
S.G. 3.07 neg. 
R.R. 4.45 pos. 
M.G. 2.56 pos. 
S.C. 3.2 pos. 
S.C. 2.6 pos. 
C.A. 3.75 pos. 
T.G. 3.14 neg. 
V.M. 2.65 pos. 
PatientN. ApheresisCD34+ x 10^6/kgRT-PCR
T.M 4.55 pos. 
O.I 3.34 neg. 
V.E. 3.33 neg. 
S.G. 3.07 neg. 
R.R. 4.45 pos. 
M.G. 2.56 pos. 
S.C. 3.2 pos. 
S.C. 2.6 pos. 
C.A. 3.75 pos. 
T.G. 3.14 neg. 
V.M. 2.65 pos. 

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