Collection, analysis and transplantation of Ph-negative blood precursor cells in chronic myeloid leukemia

This work represents an update of our experience on mobilization and transplantation of peripheral blood progenitor cells (PBPC) collected during the early recovery phase after chemotherapy in patients with chronic myelogenous leukemia. The collection of Ph-negative precursor cells occurred in 13/19 (68%) patients mobilized within the first year from diagnosis and not previously treated with interferon alpha (IFN-alpha). Fourteen out of 42 patients (33%) achieved Ph-negative precursors beyond 1 year from diagnosis. Eleven patients mobilized early after diagnosis were subsequently autografted with Ph-negative precursor cells. All patients are alive in hematologic remission and five of them maintain Ph-negativity in the marrow 7-15 months post-autograft. Four patients showed recurrence of Ph-positive cells (5 to 40%) within 4 to 8 months after autografting. Two patients became progressively Ph-positive after 6 months and are now 100% Ph-positive and in stable chronic phase. In the early stage of the disease the mobilization/transplantation procedure is safe and associated with very good compliance. However, occasional restoration of Ph-negative hematopoiesis could occur up to 45 months after autograft in patients undergoing the procedure beyond 1 year from diagnosis, and highly pretreated with IFN-alpha, but most patients revert to Ph-positive hematopoiesis. In an attempt to control the Ph-negative status and to prevent cytogeneic relapse, we are currently treating autografted patients with low doses of IFN-alpha and interleukin-2 (IL-2). Whether and for how long Ph-negative status can be maintained is a matter for future observation and effort.