Collection of Ph-negative progenitor cells from interferon responsive patients with chronic myeloid leukemia: effect...

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.

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.

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.

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.