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

Busulfan

OBJECTIVE

To review the current published studies evaluating the pharmacokinetics, clinical efficacy, safety, and toxicity of busulfan in pediatric and adult patients.

DATA SOURCES

English-language literature published between 1953 and 1993 was analyzed; pertinent literature was reviewed.

STUDY SELECTION

Emphasis was placed on pharmacologic studies and clinical trials involving busulfan therapy both in myeloproliferative disorders and in conditioning regimens for autologous or allogeneic bone marrow transplantation.

DATA EXTRACTION

Data from both pediatric and adult studies were evaluated; emphasis was placed on the relationship between plasma concentrations of busulfan and its efficacy and toxicity.

DATA SYNTHESIS

Busulfan has been used widely at conventional dosages (1-12 mg/d) for the treatment of patients with chronic myelogenous leukemia (CML). Busulfan at high doses (usually 16 mg/kg) given with other cytotoxic drugs (especially cyclophosphamide) is a common preparative regimen in patients undergoing allogeneic or autologous bone marrow transplantation (BMT) for acute or chronic leukemia and other nonmalignant disorders (e.g., hemoglobinopathies, inborn error of immune system, congenital metabolic disorders). Pharmacokinetics of high-dose busulfan are age-dependent. Busulfan systemic exposure and, thus, tissue and tumor exposure are lower in children than with adults. Relationships between toxicity (principally neutropenia, hepatic veno-occlusive disease, incidence of seizures) and drug exposure were found for busulfan.

CONCLUSIONS

Busulfan is a useful, sufficiently safe drug in the treatment of patients with CML. At higher dosages, busulfan is a fundamental part of myeloablative therapies for patients undergoing BMT. As the pharmacokinetics and metabolism of busulfan is further understood, there is great potential for improving treatment outcome. An assessment of maximal tolerated exposure determined by therapeutic drug monitoring may decrease the incidence and lethality of regimen-related toxicities.

Hydroxyurea enhances 3'-azido-3'-deoxythymidine (AZT) cytotoxicity in human chronic myeloid leukemia models

In this report we have evaluated the cytotoxic activity of 3'-azido-3'-deoxythymidine (AZT) used in combination with hydroxyurea (HU), an agent which disrupts de novo thymidylate synthesis. In 2 chronic myeloid leukemia (CML) cell lines, K562 and RWLeu4, the IC50 of AZT was 8 mumol/l and 28 mumol/l respectively, after a 5-day exposure, and the IC50 of HU was 80 mumol/l and 70 mumol/l respectively. In the presence of various concentrations of HU (1 mumol/l-100 mumol/l) the IC50 of AZT in both cell lines was significantly reduced and subsequent isobologram analysis revealed synergistic activity. Similarly, analysis of [3H]AZT incorporation into the DNA fraction of these cells indicated that exposure to AZT+HU resulted in an increased incorporation of AZT into DNA when compared to incubation in AZT alone. Biochemically, this effect appeared to be related to a decrease in dTTP pools caused by HU. The combination AZT+HU has also been demonstrated to exert a synergistic effect in inhibiting colony growth of bone marrow granulocyte-macrophage progenitors (CFU-GM) from patients affected by Ph1+ CML in chronic phase. These results are promising in view of a possible in vivo utilization of this drug combination.

Interferon alfa-2b in acute- and chronic-phase chronic myelogenous leukaemia: initial response and long-term results in 54 patients

Fifty-four patients with Ph1-positive chronic myelogenous leukaemia (CML) (48 with chronic-phase and six acute-phase disease) were treated with interferon alfa-2b subcutaneously (s.c.). The starting dose was 4 million units (MU)/m2 body surface area daily. It was reduced in parallel with serially determined leucocyte counts, and minimal effective doses were given as maintenance after achieving remission. Haematological remissions were induced in 22 of the 48 patients (46%) with chronic-phase disease. Thirteen patients (27%) revealed partial haematological remission and another 13 no response to treatment. No complete remission could be induced, although minor or partial cytogenetic responses were seen in 16 patients (33%). Moreover, a bcr-abl reduction was detected on Southern blot analysis in two patients. In chronic-phase disease, results of treatment were influenced by elapsed time after diagnosis, extent of previous treatment and interferon dosage. No beneficial effects of interferon were detected in the six patients with acute-phase disease. Principal acute side effects were fever and flu-like symptoms at the beginning of the therapy, which usually subsided within 3-7 days. Chronic side effects, especially weakness and neuropathy, were less frequent but more severe and necessitated discontinuation of treatment in 10 patients. In summary, interferon alfa-2b seems to be an effective treatment in early chronic-phase CML. Long-term effects on the course of the disease, however, must be determined.

Chemotherapy of chronic haematological malignancies

After years of stagnation in the treatment of chronic haematological malignancies, some interesting agents have emerged which might improve the prognosis of these diseases. For chronic leukaemias of lymphoid lineage, three new chemical agents, all purine analogues, seem to be of particular interest. Pentostatin is a specific inhibitor of ADA and has been shown to be highly efficient in producing CR in patients with HCL. Its relative merit compared with IFN-alpha for the treatment of HCL is being studied in ongoing randomized trials. Pentostatin is also active in B-CLL and promising activities have been demonstrated in T- or B-PLL and ATCL. Fludarabine is an analogue of adenine which is resistant to the deamination of ADA. It has been reported to be highly active for patients with both pretreated or non-treated B-CLL. CR rates of 13% with overall response rates of 57% can be achieved, even in heavily pretreated patients. Its activity in the other lymphoid malignancies is not yet known. CdA, a substrate analogue of ADA, has also produced encouraging results in B-CLL, HCL and T cell malignancies, and in some patients with just one single course. Thus far, experience with this drug comes from one institution and requires further confirmation. For chronic myeloproliferative diseases, little progress has yet been made. Although IFN-alpha seems to be active in CML and to result in cytogenetic remissions in bone marrow, a definite advantage of this biological agent over conventional chemotherapy as regards survival and life quality has not yet been proven. Allogeneic bone marrow transplantation is beneficial for those patients who are eligible. No remarkable advances have been made in the treatment of myeloproliferative disorders except for the development of an antiplatelet drug, anagrelide. This agent seems to be highly effective in controlling thrombocytosis. The relative merit of this agent as compared with IFN-alpha, as well as the impact of this agent on the survival and on life-quality of patients with myeloproliferative disorders, have yet to be defined.

Chronic myeloproliferative disorders in bone marrow biopsies

This Diagnostic Seminar intends to announce that CMPDs can be classified from BMB histologically by a rather simple system, which can be applied by interested histopathologists successfully. The rationale of this classification is to stay within the groups of diseases which are outlined by clinical findings including the peripheral blood and bone marrow smears. The concept of traditional classification as given by the WHO and textbooks, however, has to be revised as follows (1) Primary diseases of CMPDs must be distinguished from advanced disorders. Primary diseases are CML, P. vera, Thrombocythemia, CMGM, and unclassifiable CMPD. (2) Idiopathic, primary myelosclerosis of the bone marrow is a reactive feature consecutive to neoplastic transformation of hematopoiesis, i.e. myeloproliferation. (3) Advanced disorders comprise (3.1.) excess of blasts and blast crisis, and (3.2.) early myelosclerosis, myelosclerosis and myelofibrosis, advanced myelofibrosis. Advanced disorders are designated by a composed term classifying them among the groups of primary disease and specifying the advanced stage by a suffix, so that the underlying disease remains coining the term, even in unclassifiable cases in which only CMPDs can be applied. (4) The CML group must be subtyped into CML of common type versus that with increase or predominance of megakaryocytes. By this system of classification, it seems possible to classify and type the spectrum of variations occurring among CMPDs to a satisfying result.

Polycythemia vera. A clinical study of 141 patients

The clinical course of 141 unselected patients (64 m, 77 f, median age 59) with polycythemia vera (PV), treated during the period 1967 to 1986 was analyzed to study prognostic factors and the correlation between treatment strategies and complication rates. Therapy was performed according to a prospectively defined treatment protocol. Primary control of the disease was achieved by phlebotomy. Marrow suppression by radioactive phosphorus or low dose busulphan was used only as a second-line therapy or to lower high platelet counts. The clinical course of the patients was characterized by a low rate of acute leukemia (4%) and a high rate of thromboembolic complications (40%). Myelofibrosis developed in 17 patients (12%). Median survival of the patents was 9.4 years. The prognostic influence of several parameters at the time of diagnosis was tested: age, sex, spleen size, percentage of blood blasts + promyelocytes, leucocyte count, platelet count, hemoglobin, hematocrit, reticulocyte count and the values of the lactate-dehydrogenase (LDH) and the alkaline neutrophil phosphatase (ANP) all had no significant influence on the length of survival. The prognosis of PV patients with atypical disease presentation at diagnosis was not different from patients with typical disease.

Budd-Chiari syndrome and thrombosis of other abdominal vessels in the chronic myeloproliferative diseases

Of 501 patients with chronic myeloproliferative diseases (c-MPD) 18 developed thrombosis of major abdominal vessels including 6 with hepatic vein thrombosis (Budd-Chiari syndrome). The complication was seen in 14 of 140 (10%) patients with polycythemia vera (PV), 3 of 23 (13%) patients with essential thrombocythemia (ET), 1 of 106 (1%) patients with idiopathic myelofibrosis (IMF), and none of 232 patients with chronic myelogenous leukemia (CML). Leading symptoms and signs were abdominal pain, progressive splenomegaly, widening abdominal girth, ascites, venous collaterals, and nausea and vomiting. The diagnostic modalities with highest specificity were angiography and explorative laparotomy. A causal relationship between the thrombotic event and hematocrit, thrombocyte count, or hemostatic abnormalities at the time of diagnosis could not be established. Detailed laboratory tests of platelet function and coagulation and fibrinolytic parameters of 5 surviving patients did not show any specific defect. Despite medical and surgical intervention, 39% of the patients died within 2 months after diagnosis of the thrombosis. The majority of the survivors developed further complications like liver cirrhosis with portal hypertension and esophageal varices or the short bowel syndrome after extensive bowel resection for mesenterial infarction.

A phase I/II study of recombinant interferon alpha 2a and hydroxyurea for chronic myelocytic leukemia

Nine previously untreated patients with Philadelphia chromosome-positive chronic myelocytic leukemia (CML) were treated with recombinant interferon alpha 2a (rIFN-alpha 2a) and hydroxyurea. Patients received 6 X 10(6) U rIFN-alpha 2a daily for the first week and 3 X 10(6) U rIFN-alpha 2a daily for the second week. As maintenance treatment starting on day 15, patients received 3 X 10(6) U rIFN-alpha 2a 3 times a week. Simultaneously, hydroxyurea was given, starting at a dose of 40 mg/kg on day one. The maintenance dosage was adjusted to the white blood cell count. Two patients responded with complete hematological remissions but without cytogenetic and molecular-genetic improvements. Seven patients responded with partial hematological remissions. Response to therapy was rapid; normal white blood cell counts were reached after a median of 12 days. The doses of rIFN-alpha 2a and hydroxyurea needed to keep the leucocyte count in the normal range were low (3 X 10(6) U rIFN-alpha 2a 3 times per week, 0.5-1.5 g hydroxyurea/day). Acute toxicity of the combination therapy consisted of fever (9 of 9 patients), flulike symptoms (7 of 9 patients), pruritus and/or rash (3 of 9 patients) and evidence of a tumor cell lysis syndrome (1 of 9 patients). The side effects were not dose-limiting. Combination therapy with rIFN-alpha 2a and hydroxyurea for CML is well tolerated and allows quick and effective hematological control of the disease.

Treatment of thrombocytosis in myeloproliferative disorders with interferon alpha-2a

In an open prospective pilot trial, we tested the effect of recombinant interferon alpha-2 a (rIFN alpha-2 a) on thrombocytosis in myeloproliferative disorders (MPD). Since October 1986, 13 patients with MPD (4 with chronic granulocytic leukemia, 4 with polycythemia vera, 3 with essential thrombocythemia and 2 with myeloid metaplasia) were treated with rIFN alpha-2 a. Platelet counts decreased in all treated patients within 2 to 10 weeks from a median value of 1,050 x 10(9)/l (range 610-1,940 x 10(9)/l) to 340 x 10(9)/l (range 230-495 x 10(9)/l). The response was dose-dependent. In 11 patients we observed a simultaneous reduction of the white blood cell count. Six patients still continue the IFN alpha-2 a therapy. In 7 treatment was discontinued, because of chronic side effects in 3, and because of noncompliance in one. In these patients, thrombocytosis recurred after discontinuation of the therapy. These results show that rIFN alpha-2 a is effective in controlling thrombocytosis in MPD. However, the long-term benefit of interferon in these disorders remains to be established.