Karyotypic conversion in Ph1-positive chronic myeloid leukaemia with combination chemotherapy

Mobilisation and reinfusion of Philadelphia negative peripheral blood mononuclear cells in chronic myeloid leukaemia with hydroxyurea and G-CSF

Unmanipulated autologous transplantation of marrow of peripheral blood stem cells has been performed in small numbers of patients with CML for many years. More recently there has been interest in attempting to 'purge' the autograft of clonal cells as defined by the presence of the Philadelphia chromosome or BCR-ABL rearrangement. One method by which this might be achieved in vivo has been developed in Genoa and involves the administration of high dose chemotherapy and G-CSF followed by peripheral blood stem cell collection. These collections are frequently devoid of Philadelphia positive cells and the hope is that this will enhance the effects of subsequent autograft. We have investigated the use of a less toxic regimen for this procedure using oral hydroxyurea and G-CSF. In this review we describe the background to autografting in CML and the development of strategies to mobilise Philadelphia negative cells into the peripheral blood. We go on to present an update of our data using hydroxyurea and discuss some of the practical and theoretical issues behind the procedure.

Autografting for chronic myeloid leukaemia

For most chronic myeloid leukaemia (CML) patients the option of a potentially 'curative' allogeneic stem cell transplant is not available because of age or lack of donor. Interferon alpha appears to extend survival when used in the chronic phase of the disease but probably does not produce long-term disease-free survivors. Autografting is being actively explored as a therapeutic option which may improve on the survival data seen with interferon and numerous different autografting methodologies are being investigated. While it seems reasonable to hope that a suitably robust and safe approach to autografting may improve survival it is unlikely with current technology that long-term disease-free survival will be achieved. To date no compelling trial data are available to confirm the efficacy of autografting but large prospective randomized studies are underway to investigate whether autografting can indeed extend survival for CML patients who do not have the option of an allograft.

Stem cell kinetics

Chronic myeloid leukaemia (CML) is a transplantable multi-lineage disease. In its initial chronic phase, the leukaemic clone exhibits a hierarchical structure that closely resembles normal haematopoiesis. Thus assays for in vitro colony-forming cells (CFC) and their more primitive precursors identified as long-term culture-initiating cells (LTC-IC) detect subsets of Ph+/BCR-ABL+ cells which cannot be readily distinguished from their normal counterparts. The use of these assays to examine the numbers, properties, genotype, distribution and regulation of primitive progenitors in patients' blood and marrow samples have revealed a number of unique and unexpected findings. These suggest that the indolent nature of the chronic phase of the disease may be explained by competing effects of the BCR-ABL gene product on the commitment to differentiate, control of cell cycle progression and apoptosis. As a result, the amplification of BCR-ABL+ stem cells is constrained but the expansion of their progeny is enhanced and, on the granulocyte pathway, this expansion proceeds unchecked to the stage of mature end cell production resulting in the leukaemic picture observed.

Current aspects of drug therapy in Philadelphia-positive CML: correlation of tumor burden with survival

One therapeutic concept in chronic myeloid leukemia (CML) assumes that a reduction of clonal genetically unstable cells also reduces the rate of secondary genetic changes and thereby postpones blast crisis. According to this concept, the degree of reduction of tumor burden should correlate with a prolongation of survival. The recent literature, in particular on controlled studies of IFN, hydroxyurea or intensive chemotherapy is reviewed and analyzed with regards to this concept. In chronic phase CML, intensity of treatment as determined by the degrees of WBC suppression, and, more recently, of cytogenetic remission, as measures of the reduction of tumor burden appear to correlate directly with survival. The superiority of a therapeutic regimen in chronic phase CML seems to primarily depend on whether its pharmacology permits a sufficiently high dosage to achieve the necessary reduction of tumor burden. The concept underlies present strategies that try to prolong survival in CML by IFN alone or in combination with intensive chemotherapy, by hydroxyurea, alone or in combination with IFN, and by high-dose chemotherapy followed by autografting.

Benign hematopoietic progenitors in chronic myeloid leukemia: current status and future prospects

Many patients with chronic myeloid leukemia (CML) retain a certain degree of normal hematopoiesis at disease presentation. This fact, suspected on the basis of cytogenetic findings, has been confirmed by long-term bone marrow cultures (LTBMC) and the combined use of phenotypic and molecular studies. Based on the lack of HLA-DR expression, it has been possible to recognize a benign subpopulation within the stem-cell compartment in CML. Different in vitro techniques have been developed for the selection of these benign progenitors, including LTBMC, marrow incubation with cytolytic drugs or interferon, positive selection based on their phenotypic characteristics, and exposure to synthetic antisense oligodeoxynucleotides. In vivo selection with interferon or intensive chemotherapy is also possible. The primary goal of the selection of benign hematopoietic progenitors is their use for autotransplantation. To date, a few hundred CML patients have been submitted to the latter procedure using bone marrow or peripheral blood. The fact that the majority of them show evidence of persistent disease emphasizes the necessity for better selection methods of the benign progenitors, for intensifying the conditioning regimen to reduce the tumor burden as much as possible, and for the use of adjuvant therapy post-transplantation. Future trends include the refinement of positive selection methods, negative selection by taking advantage of the different stromal adhesiveness of the benign and malignant progenitors, or the use of autologous natural killer cells, antisense oligodeoxynucleotides, or specific antibodies to the bcr/abl junction region, and retroviral marking to determine the origin of relapse in autologous transplantation.

Residual Ph-negative stem cells in chronic myeloid leukemia--sometimes or always?

Some patients with Philadelphia (Ph) chromosome-positive chronic myeloid leukemia (CML) may achieve partially or completely Ph-negative hemopoiesis after treatment with high doses of cytotoxic drugs or interferon-alpha at standard dosage. This observation leads to three important questions: 1) are Ph-negative myeloid cells in such patients strictly normal? 2) can such Ph-negative cells be identified in all newly diagnosed patients or only in a minority? and 3) what is the basis for the proliferative advantage manifested by CML cells and why might it be temporarily lost as a result of treatment? The mechanisms that might prevent the proliferation of normal cells in an environment of Ph-positive cells and the relevance of these questions to the design of a strategy aimed at obtaining complete remission in the majority of patients are considered. Such a strategy might incorporate autografting with Ph-negative stem cells harvested during the recovery phase of high dose chemotherapy.

Cytogenetic Remissions in Chronic Myelogenous Leukemia Using Interferon Alpha-2a and Hydroxyurea with or without Low-Dose Cytosine Arabinoside

Twenty-four patients with Philadelphia positive (Ph +) chronic myelogenous leukemia including 12 who were previously untreated, received recombinant interferon alpha-2a (IFN) (5 × 10(6) U/m(2)/d) and hydroxyurea (HU) (50 mg/kg/d) at the induction phase. Low dose cytosine arabinoside (Ara-C) (10-20 mg/m(2)/d, 10 to 15 d/month) was added during IFN maintenance therapy at month 3 to 11 in cases with no cytogenetic response and/or hematological resistance. A complete hematological remission was achieved rapidly (med 5 weeks), with the induction regimen in 9/12 previously untreated patients, and obtained or maintained in 9/12 patients who had already received conventional chemotherapy. Thirteen patients (8 untreated, 5 previously treated) showed a cytogenetic improvement and 9 of them had complete suppression of the Ph + clone after 3 to 24 months of treatment. Six patients had durable complete cytogenetic remissions lasting 6 + to 15 + (med 9 +) months. Two of the patients with minor or no cytogenetic response progressed to blastic crisis and died shortly thereafter. The low-dose Ara-C-IFN regimen was well tolerated and no intercurrent infections or bleeding was recorded. This preliminary data suggests a high incidence of hematologic remissions and cytogenetic response with the combination of IFN alpha, HU and low dose Ara-C.

Randomized study on the treatment of chronic myeloid leukemia (CML) in chronic phase with busulfan versus hydroxyurea versus interferon-alpha

For palliative therapy during the chronic phase of CML busulfan has proved to be the drug of choice. During the past years hydroxyurea and also interferon-alpha have gained increasing significance since they might prolong the duration of the chronic phase. In a multicenter study it is being determined, whether the use of hydroxyurea or of interferon-alpha instead of busulfan prolongs the duration of the chronic phase of Philadelphia positive CML. Additional goals are the examination of whether the types of disease evolution and the terminal phases differ between the treatment groups, and the prospective recognition of prognostic criteria for the duration of the chronic phase of CML. By December 31, 1987, 326 CML-patients had been randomized, 150 for busulfan, 150 for hydroxyurea and 26 for interferon-alpha. The average age is 50 years. 59 patients reached the end of the chronic phase, 55 died. The mean observation time of all patients is 1.34 years. At present no significant difference in survival is recognizable between the busulfan and hydroxyurea groups. Fewer adverse effects have been observed in the hydroxyurea group. Philadelphia chromosome negative patients show a higher average age and tend to have lower white blood cell and platelet counts. The number of patients having received interferon-alpha is still too small to allow evaluation. This report intends to document organization and progress of this study which to our knowledge is, at present, the largest ongoing prospective multicenter study on the therapy of CML.

Evidence for a selective antileukemic effect of cytosine arabinoside in chronic granulocytic leukemia

On the basis of in-vitro studies indicating that low concentrations of cytosine arabinoside exert preferential inhibition of granulocyte-macrophage colony-forming cells from patients with chronic granulocytic leukemia vs normal subjects, we treated two outpatients with low doses of this agent, administered by subcutaneous infusion for 12-31 days. Both patients continued their usual activities, including employment, during these infusions. They exhibited only Ph-positive metaphases at entry into the protocol but in both cases, Ph-positive cells were reduced to approx. 10% of marrow metaphases, after 2-3 successive infusions. Both patients exhibited significant increases in Ph-positive cells, to 46 and 72% of marrow metaphases, during subsequent chemotherapy with hydroxyurea, in dosage sufficient to maintain granulocytopenia and a normal serum B12 level. After additional cytosine arabinoside, both patients again showed decreases in Ph-positive cells, to 7% (p less than 0.01) and 19% (p less than 0.0001), respectively. This clinical experience is consistent with the conclusion that cytosine arabinoside (but not, hydroxyurea) exerts a selective antileukemic effect in some patients with CGL.

Attempted prevention of blast crisis in chronic myeloid leukemia by the use of pulsed doses of cytosine arabinoside and cis-chloronitrosurea during the course of busulfan-maintained remission

We performed this chemotherapeutic trial to try to delay the onset of the blast crisis of chronic myeloid leukemia (CML) by pulsing doses of drugs most likely to be effective against emerging "blast" cells characteristic of acute phase disease. A randomized trial in patients with CML comparing busulfan maintenance to busulfan maintenance plus pulsed doses of cytarabine and lomustine did not yield any differences in either time to blast crisis or death.

Chromosome abnormalities in CML

The Ph chromosome is the hallmark of CML, where it is found in more than 90% of the cases. Cytogenetically, it usually results from a t(9;22)(q34;q11). The Ph arises in a stem cell and in chronic phase is found in all haematopoietic cell lineages, although it causes only increased granulopoiesis, and sometimes increased thrombopoiesis; furthermore blast crisis may occur in all differentiative patterns of the pluripotent stem cell. Recently, molecular investigations of Ph positive CML cases have revealed a consistent genomic recombination between two genes, BCR on chromosome 22 and the ABL oncogene. The latter is translocated from 9q34, its normal site, to the 22q- or Ph chromosome. This molecular rearrangement expresses a unique 8.5 kb BCR-ABL hybrid mRNA transcript, that encodes an altered BCR-ABL protein of approximately 210 kD with enhanced in vitro tyrosine kinase activity. The breakpoints on chromosome 22q- are clustered in a 5 kb DNA fragment, allowing their study using Southern blot analysis. Cytogenetic variant forms of the Ph translocation involving three or more chromosomes are found in about 5% of the cases. Southern blot and in situ hybridization studies have demonstrated that these variants are cytogenetically more complex than the standard t(9;22) but molecularly they show the same essential genomic recombination. This is also true for a small number of cases of Ph negative CML. Clonal progression, indicated by the presence of clonal, non-random chromosome abnormalities, in addition to the Ph is rare during chronic phase but is found in 80% of blast crisis. These additional aberrations may precede BC by weeks or months and have therefore a clear prognostic value. Ph is not restricted to CML, since it is also found in ALL (20% of adult cases) and rarely in AML. Ph in acute leukaemia is cytogenetically indistinguishable from Ph in CML, but molecular studies have shown that in 50% of the cases the breakpoint on chromosome 22 is different from the very consistent and characteristic breakpoint in CML. Nevertheless genomic recombination takes place that results in a novel ABL protein at least in some of the cases. Despite extensive cytogenetic and molecular investigations, the mechanisms underlying the formation of the Ph as well as the pathogenesis of Ph positive CML are still unknown but are now the object of intensive research.

Preferential inhibition by cytarabine of CFU-GM from patients with chronic granulocytic leukemia

Granulocyte-macrophage colony-forming (CFU-GM) cells from peripheral blood of normal subjects and patients with chronic granulocytic leukemia (CGL) were cultured in soft agar. Drugs under study were added in a liquid overlay 2 days after initiation of cultures, providing prolonged exposure to these agents thereafter. Dose-dependent inhibition of colony growth was recorded with each of eleven agents examined, and at the higher concentrations tested, colony formation was often completely suppressed. Cytarabine showed selectivity against CFU-GM from patients in the chronic stage of CGL (P = 0.006); the median 50% inhibitory concentration for 12 such patients was 3.4 ng/ml versus 11.8 ng/ml for 15 healthy subjects. Such selectivity was not found with busulfan, hydroxyurea, mercaptopurine, thioguanine, daunorubicin, vincristine, vinblastine, methotrexate, desacetylmethylcolchicine, and trimethylcolchicinic acid. One other group has also reported a preferential effect of cytarabine against colony-forming cells from patients with CGL, and this appears to be the only drug for which such selective activity has been recorded to date.

Terminal-phase chronic myelogenous leukemia: approaches to treatment

The prognosis of patients with CML has improved little in the past 50 years. The relatively benign chronic phase invariably deteriorates to a refractory and rapidly fatal terminal phase. This terminal stage has been found to have two major subtypes as defined by morphologic, cytochemical, immunologic, and enzymatic criteria--myeloblastoid and lymphoblastoid. Aggressive combination chemotherapy has achieved minimal improvement in survival once the terminal phase has begun, perhaps because only Ph1-positive stem cells remain to repopulate the marrow at this stage. Bone marrow transplantation has also been unsuccessful as therapy for the terminal phase, possibly because the patients are too debilitated to tolerate transplantation once the terminal phase has begun. Combination chemotherapy has been applied in an effort to eliminate the Ph1 chromosome-containing clone during the chronic phase. This goal has not yet been consistently achieved. Chemotherapy has also not been able to delay the onset of the terminal phase nor to prolong survival. Even in those patients in whom the Ph1 chromosome-containing clone has been eliminated, relapse to the chronic phase with return of the Ph1 chromosome has generally occurred within a brief period of time. Bone marrow transplantation during the chronic phase may hold the promise of true cure for CML, with permanent elimination of the malignant clone. However, the chronic phase can be unpredictably long and patients in the chronic phase often have few, if any symptoms. Therefore, there has been a reluctance to employ drastic therapy during the chronic phase. Techniques to predict the transformation to the terminal phase prior to overt morphologic or clinical conversion are now being developed. It may be possible in the future to attempt HLA-matched sibling donor bone marrow transplantation at the earliest signs of transformation from the chronic to the terminal phase. In this manner, optimal survival might be achieved by allowing patients to be maintained in the chronic phase for as long as possible prior to the initiation of aggressive therapy. Until this is routinely possible, continued research designed to improve the therapy of the terminal phase must be pursued. These attempts are likely to include the development and evaluation of new chemotherapeutic agents, novel methods of administration of existing drugs to better exploit their pharmacokinetics (for example, continuous infusion), and the utilization of newly described treatment approaches (such as the use of "differentiating" agents in an attempt to prevent progression to blastic transformation).(ABSTRACT TRUNCATED AT 400 WORDS)

Results of a prospective randomized trial of early splenectomy in chronic myeloid leukemia. The Italian Cooperative Study Group on Chronic Myeloid Leukemia

The role of early splenectomy in the management of chronic myeloid leukemia (CML) was investigated in a multicentric study with 21 contributing Hospitals. One hundred eighty-nine patients younger than 66 years of age and previously untreated, were first seen between November 1974 and May 1977, were randomized to splenectomy or to nonsplenectomy , were given the same chemotherapy (busulfan, and courses of arabinosyl cytosine, 6-thioguanine, and daunomycin), and were followed up for more than 5 years. Median survival was 45 months. No relationship of splenectomy to survival length could be shown either in the whole series, or in several subgroups that were selected according to presentation features and stage classification. Thromboembolic and vascular accidents were more frequent in the splenectomy group, and this was associated with more difficult control of platelet count. Early splenectomy is not recommended for treatment of CML.

Twenty-five year survival of chronic granulocytic leukaemia with spontaneous karyotype conversion

Following busulphan-induced bone marrow hypoplasia a woman with chronic granulocytic leukaemia has survived 25 years from diagnosis. Since the last course of busulphan therapy in 1959 she has remained in clinical and haematological remission. Repeated cytogenetic analysis of bone marrow showed Philadelphia chromosome mosaicism with a minority of abnormal metaphases till 1969. Analysis of 150 metaphases in 1982 revealed no cells containing the Philadelphia chromosome. The possible significance of this spontaneous karyotype conversion is discussed.

Autologous marrow transplantation after karyotypic conversion to normal in blastic phase of chronic myelocytic leukemia

A patient with blastic transformation of Philadelphia chromosome-positive chronic myelocytic leukemia was treated with acridinyl anisidide, which resulted in conversion to a normal karyotype. At that time, bone marrow was harvested and cryopreserved. After relapse, the patient was treated with cyclophosphamide and fractionated total body irradiation followed by autologous marrow transplantation. Serial karyotypes and blood counts, determined up to 14 months after transplantation, remained normal.

Long-term marrow culture reveals chromosomally normal hematopoietic progenitor cells in patients with Philadelphia chromosome-positive chronic myelogenous leukemia

We found that when marrow cells from four patients with newly diagnosed Philadelphia chromosome-positive chronic myelogenous leukemia were maintained in culture for two to four weeks, a previously undetectable population of chromosomally normal hematopoietic cells (including erythroid, granulopoietic, and pluripotent progenitors) became readily demonstrable in three cases. Time-course studies showed that in such cultures the dominant Philadelphia chromosome-positive population rapidly disappeared, in contrast to coexisting chromosomally normal progenitors, which remained detectable for periods of two to three months. Long-term marrow cultures thus offer a new approach to the assessment of a suppressed but functionally intact population of chromosomally normal hematopoietic stem cells in patients with chronic myelogenous leukemia.

Treatment of chronic granulocytic leukemia with chemoradiotherapy and transplantation of marrow from identical twins

Twelve patients in the chronic phase of Ph1 (Philadelphia)-positive chronic granulocytic leukemia (CGL) received chemoradiotherapy and marrow from their normal, identical twins. All had a complete remission, with disappearance of all Ph1-positive cells. One patient died of pneumonitis while in remission. Three had a cytogenetic relapse 22 to 30 months after grafting; only one of these three entered blast crisis and died. Eight remain in complete remission 21 to 65 months (median, 30) after transplantation. Thus, the Ph1-positive clone can be ablated and blast crisis delayed or prevented. Of 10 patients with CGL who received transplants during the terminal phase, eight died soon after, one is in complete remission 11 months after receiving a second graft, and one remains in complete remission 71 months after transplantation. This experience suggests to us that every patient with CGL and an identical twin should receive a marrow graft, preferably in the chronic phase. On the basis of our results, trials of allogeneic-marrow transplantation for CGL seem justified.

Buffy coat autografts for patients with chronic granulocytic leukaemia in transformation

We have treated 20 patients with chronic granulocytic leukaemia (CGL) in transformation with cytotoxic drugs or with cytotoxic drugs and whole-body irradiation followed by transfusion of autologous blood cells collected at diagnosis and stored in liquid nitrogen. The mean number of nucleated cells autografted was 25.1 X 10(8)/kg (range: 12.5-40.1). Full myeloid engraftment occurred in 18 patients; it was partial in one patient and unassessable in another. The median survival for the 20 patients post-graft was 14 weeks. Two patients are alive, one now in recurrent transformation, and one in second chronic phase that has lasted 52 weeks. For the 18 patients who died the mean survival was 24 weeks (range: 2-125). Two patients with predominantly myelosclerotic transformation showed evidence of engraftment. One patient successfully autografted developed features consistent with graft-versus-host disease which proved fatal. We conclude that autografting may offer substantial palliation for some but not all patients with CGL in transformation.