Background and objective: The observation that patients with chronic myeloid leukemia (CML) may relapse following stem cell transplantation because of Philadelphia positive cells contaminating the graft have led to a variety of strategies to reduce this contamination. This study investigate the feasibility of collective, Ph-re cells from patients with CML in chronic phase.
Design and methods: A total of 18 patients with chronic myeloid leukemia in chronic phase who had responded to varying degrees to treatment with interferon-a (IFN) were subjected to mobilization with granulocyte colony-stimulating factors and peripheral blood progenitor cell collection. Nine patients were in complete cytogenetic remission (CCR) and nine were partial responders. IFN was stopped 2 to 4 weeks before the procedure. G-CSF was given by subcutaneous injection once daily at a dose of 10 microg/kg.
Results: Five patients underwent one collection procedure only, 10 underwent two procedures and 3 patients had three collections. The median number of nucleated cells (NC) per patient collected was 10.2 x 10(8)/kg (4.4-19.7) and the median number of CD34(+) cells was 2.5 x 10(6)/kg (0.4-9.4). Analyzable cytogenetic data were available for 26/34 (76%) leukapheresis procedures. The median percentage of Ph- negative metaphases for patients in CCR was 100% (73-100). Patients not in CCR had a higher level of Ph-positive cells in their collections (median 23%, range 0-79%, p=0.01). Of the nine patients in CCR, 8 had at least one apheresis from which progenitor cells were 100% Ph-negative; conversely, patients not in CCR had detectable Ph-positive cells in every collection. Four patients have undergone autologous stem cell transplantation.
Interpretation and conclusions: It was possible to collect sufficient Ph negative progenitor cells from patients in CCR but collections from other patients contained significant numbers of Ph-positive cells.