Autologous stem cell transplantation in chronic myeloid leukaemia using Philadelphia chromosome negative blood progenitors mobilised with hydroxyurea and G-CSF

Successful mobilization of Ph-negative blood stem cells with intensive chemotherapy + G-CSF in patients with chronic myelogenous leukemia in first chronic phase

The aim of the study was to investigate the feasibility of mobilizing Philadelphia chromosome negative (Ph-) blood stem cells (BSC) with intensive chemotherapy and lenograstim (G-CSF) in patients with CML in first chronic phase (CP1). During 1994-1999 12 centers included 37 patients <56 years. All patients received 6 months' IFN, stopping at median 36 (1-290) days prior to the mobilization chemotherapy. All received one cycle of daunorubicin 50 mg/m2 and 1 hour infusion on days 1-3, and cytarabine (ara-C) 200 mg/m2 24 hours' i.v. infusion on days 1-7 (DA) followed by G-CSF 526 microg s.c. once daily from day 8 after the start of chemotherapy. Leukaphereses were initiated when the number of CD 34+ cells was >5/microl blood. Patients mobilizing poorly could receive a 4-day cycle of chemotherapy with mitoxantrone 12 mg/m2/day and 1 hour i.v infusion, etoposide 100 mg/m2/day and 1 hour i.v. infusion and ara-C 1 g/m2/twice a day with 2 hours' i.v infusion (MEA) or a second DA, followed by G-CSF 526 microg s.c once daily from day 8 after the start of chemotherapy. Twenty-seven patients received one cycle of chemotherapy and G-CSF, whereas 10 were mobilized twice. Twenty-three patients (62%) were successfully (MNC >3.5 x 10(8)/kg, CFU-GM >1.0 x 10(4)/kg, CD34+ cells >2.0 x 10(6)/kg and no Ph+ cells in the apheresis product) [n = 16] or partially successfully (as defined above but 1-34% Ph+ cells in the apheresis product) [n = 7] mobilized. There was no mortality during the mobilization procedure. Twenty-one/23 patients subsequently underwent auto-SCT. The time with PMN <0.5 x 10(9)/l was 10 (range 7-49) and with platelets <20 x 10(9)/l was also 10 (2-173) days. There was no transplant related mortality. The estimated 5-year overall survival after auto-SCT was 68% (95% CI 47 - 90%), with a median follow-up time of 5.2 years.We conclude that in a significant proportion of patients with CML in CP 1, intensive chemotherapy combined with G-CSF mobilizes Ph- BSC sufficient for use in auto-SCT.

Autologous hematopoietic cell transplantation for chronic myelogenous leukemia

Experimental and clinical evidence for persistence of polyclonal Philadelphia chromosome negative (Ph-) progenitors in chronic myelogenous leukemia (CML) patients has provided the rationale for autologous transplantation. Clinical trials of autologous transplantation suggest that this procedure can induce cytogenetic remissions in a subset of patients and may be associated with longer-than-expected patient survival. Most autologous transplant recipients, however, continue to have evidence of persistent leukemia. Recent reports indicating that it is possible to collect sufficient numbers of Ph- peripheral blood stem cells for autologous transplantation from most patients in complete cytogenetic remission on imatinib treatment have rekindled interest in autologous transplantation in CML. Additional approaches to eliminate residual disease in autografts and to sustain cytogenetic response after transplantation, however, will be required to achieve long-term restoration of Ph- hematopoiesis. Several promising methods to improve purging of the autograft and for more effective elimination of residual leukemia are being explored.

Chronic myelogenous leukemia: elements of conventional chemotherapy and an overview of autografting in the treatment of the chronic phase

Chronic myelogenous leukemia (CML) consists of a clonal malignancy that arises from a pluripotent hematopoietic stem call. In most cases, neoplastic cells are characterized by the formation of a shortened chromosome 22 called the Philadelphia chromosome. It results from a reciprocal translocation between long arms of chromosomes 9 and 22. A rearranged gene (bcr-abl) is the consequence of this translocation, and it may be considered as the first step toward leukemic transformation. Conventional chemotherapy of CML in the chronic phase is unable to suppress the Ph+ leukemic clone. The treatment with the IFNalpha may induce an overall cytogenetic response rate of 40-50% of patients. Autografting for patients with CML in chronic phase may induce a 53% overall cytogenetic response rate with a duration of disease-free time and survival from the autograft ranging, respectively, from 4 to 24 mo and from 8 to 40 mo.

Analysis of CD34+ cell subsets in stem cell harvests can more reliably predict rapidity and durability of engraftment than total CD34+ cell dose, but steady state levels do not correlate with bone marrow reserve

In peripheral blood stem cell transplantation (PBSCT), the number of CD34+ cells transplanted has been shown to correlate well with both rapidity and durability of engraftment. However, it is clear that engraftment does not necessarily correlate with total CD34+ cell numbers in some patients. Consequently, there is increasing interest in evaluating the role of CD34+ subsets in haemopoietic recovery as a more accurate marker of harvest quality. We analysed the numbers of CD34+ cell subsets, namely Thy-1+, L-Selectin+ and CD38-, and correlated this with engraftment in 86 patients undergoing PBSCT. Adequate engraftment was defined as being a platelet count greater than 50 x 10(9)/l and a neutrophil count greater than 1.0 x 10(9)/l. CD34+L-Selectin+ provided the best prediction of engraftment rapidity, although the improvement over total CD34+ cell dose was minor. Only the dose of CD34+Thy-1+ cells transplanted correlated with durable engraftment. The probability of adequate 3-month engraftment increased with the dose of CD34+ cells transplanted, but 10% of patients receiving > 5 x 10(6)/kg still showed poor engraftment at 3 months. However, all patients receiving > 2.5 x 10(5)/kg CD34+Thy-1+ showed adequate engraftment at this time point. We also demonstrated that CD34+Thy-1+ progenitors were restricted to the bone marrow under normal conditions and, during stem cell mobilization, their kinetics generally paralleled total CD34+ numbers.

Mobilization of hematopoietic stem cells

Hematopoietic stem cell transplantation has been extensively exploited as a therapeutic and research modality and has revolutionized current patient care. At present, more and more medical centers use peripheral blood progenitor cells for transplantation by mobilizing hematopoietic stem cells from bone marrow to peripheral blood because of potential advantages of peripheral blood stem cell transplantation over bone-marrow transplantation. Different effective mobilization regimens have been developed recently with chemotherapeutic agents, hematopoietic growth factors or their combination. This article reviews current developments related to hematopoietic stem cell mobilization including the biology of hematopoietic stem cells, strategies for mobilization, management for mobilization failure, mechanisms of mobilization, and side effects during mobilization. Finally, the Initiation-Amplification-Emigration-Adaptation Model is proposed to help aid understanding of the mechanisms of hematopoietic stem cell mobilization and to stimulate development of novel and optimal mobilization strategies for patient care.

Quantitative evaluation of BCR-ABL amount of transcript post mobilization with G-CSF of peripheral blood stem cells from chronic myeloid leukemia patients in cytogenetic response

We studied nine patients affected by chronic myeloid leukemia (CML Ph+ and bcr-abl positive) and treated with alpha-interferon (alpha-INF) in order to: first, to evaluate the feasibility of a mobilization of peripheral blood stem cells induced by granulocyte-colony-stimulating factor (G-CSF) and the contamination by Ph+ cells and second, to quantify the amount of bcr-abl leukemia associated transcript by a quantitative assay during mobilization procedures, and post mobilization follow-up. Eight achieved a complete karyotypic remission before mobilization obtained with discontinuation of alpha-INF for few days and G-CSF at a dosage of 15 microg/kg/day for 5-7 consecutive days. By quantitative-competitive polymerase chain reaction (QC-PCR) assay, all the leukaphereses and bone marrow samples during post mobilization follow up were studied to determine the amount of bcr-abl transcript. Karyotypic and molecular analysis on evaluable leukapheresis showed that all the harvests were Ph negative and bcr-abl positive: in seven cases the levels of bcr-abl transcript were higher or equal to the pre-apheresis status. In three out of four patients, who underwent more than one leukapheresis procedure, we noticed a decreasing amount of bcr-abl contamination from the first to the last apheresis. Our results suggest that in patients who achieved a complete or major cytogenetic conversion with alpha-INF, it is possible to obtain a sufficient amount of PBSC for autografting by leukapheresis following priming G-CSF therapy and that the amount of neoplastic transcript does not seem to increase.

Mobilisation of haemopoietic progenitors in CML: a second course of intensive chemotherapy does not improve Ph-negativity in stem cell harvests

We collected peripheral blood stem cells (PBSC) in 19 early chronic phase CML patients following each of two consecutive cycles of intensive chemotherapy (CT) to evaluate whether an additional cycle of CT would increase Philadelphia (Ph)-negativity of the PBSC harvest. Autologous SCT (autoSCT) was performed if a major cytogenetic response (MCR) of the PBSC harvest was obtained. CT consisted of cytarabine 200 mg/ m2/day (days 1-7)/idarubicin 12 mg/m2/day (days 1-2) (cycle one) and cytarabine 2000 mg/m2/day (days 1-6)/amsacrine 120 mg/m2/day (days 1-3) (cycle two). One patient died of fungal pneumonia after the first cycle. Stem cells were harvested in 18 patients after cycle one and in 16 patients after cycle two. After the first cycle, all patients showed a cytogenetic response of their graft (MCR in eight patients: three complete, five partial), after cycle two, seven patients obtained an MCR (one complete, six partial). Seven patients became eligible for autoSCT. All patients proceeded with IFNalpha maintenance. Currently, 16 patients are alive. At the latest cytogenetic examination of bone marrow, four patients showed an MCR and four a minor response. In conclusion, although a second cycle of CT may contribute to elimination of leukemia residing in the patient, it appeared to be ineffective in improving the Ph-negativity of the PBSC graft.

Chronic myelogenous leukemia

Over the past year, new information has been reported on the biology and treatment of chronic myelogenous leukemia (CML). Chronic myelogenous leukemia is characterized by the breakpoint cluster region (BCR-ABL) chimeric gene, the product of which is p210BCR-ABL, a tyrosine kinase that gives hematopoietic cells the characteristics of excessive proliferation, resistance to physiologic apoptotic signals, and resistance to chemotherapy. Recently, investigators have attempted to 1) elucidate the mechanisms by which the BCR-ABL gene and its product initiate and maintain the malignant phenotype, 2) improve the use of the BCR-ABL gene as a diagnostic marker of disease, and 3) inhibit the expression of this gene as a therapeutic maneuver. Other investigators have tried to explain interferon's mechanism of action in the treatment of CML and to improve the safety and applicability of stem cell transplantation (SCT) as a therapy for CML.