Low-dose cytosine arabinoside in the myelodysplastic syndromes and acute myelogenous leukemia

Treatment with Low-Dose Cytarabine in Elderly Patients (Age 70 Years or Older) with Acute Myeloid Leukemia: A Single Institution Experience

Objectives

Low-dose cytarabine (LD-AraC) is still regarded as the standard of care in elderly patients with acute myeloid leukemia (AML) ‘unfit’ for intensive chemotherapy. In this study, we reported our experience with LD-AraC in patients ≥ 70 years old and compared the results to those of intensive chemotherapy, best supportive care (BSC), or hypomethylating agents in the same age population.

Methods

Between 2000 and 2014, 60 patients received LD-AraC at 20 mg once or twice daily by subcutaneous injection for 10 consecutive days every 4–6 weeks.

Results

Complete remission rate with LD-AraC was 7% versus 56% with intensive chemotherapy and 21% with hypomethylating agents. Median overall survival (OS) of patients treated with LD-AraC was 9.6 months with 3-year OS of 12%. Survival with LD-AraC was better than with BSC only (P = 0.001). Although not statistically significant, intensive chemotherapy and hypomethylating agents tended to be better than LD-AraC in terms of OS (median: 12.4 months and 16.1 months, respectively). There was no clear evidence that a beneficial effect of LD-AraC was restricted to any particular subtype of patients, except for cytogenetics. There was a trend for a better OS in LD-AraC treated patients in the setting of clinical trials as compared with those treated outside of a clinical trial.

Conclusions

Despite a trend in favor of intensive chemotherapy and hypomethylating agents over LD-AraC, no real significant advantage could be demonstrated, while LD-AraC showed a significant advantage comparatively to BSC. All this tends to confirm that LD-AraC can still represent a baseline against which new promising agents may be compared either alone or in combination.

Treatment of acute myeloid leukemia in older patients

Acute myeloid leukemia carries a dismal prognosis in patients over 60 years of age and, despite many clinical trials of both novel and conventional agents, there has been no significant improvement in overall survival during the last 30 years. Combinations of anthracyclines and cytarabine remain the cornerstone of therapy and produce complete remission in 45-55% of older patients, with a median survival of only 8-12 months. These statistics become even worse in patients over 70 years and those with unfavorable cytogenetics and/or poor performance status. Deciding which older acute myeloid leukemia patients would benefit from intensive chemotherapy is difficult and efforts are underway to improve existing risk-assessment tools. Many new agents are under development, including signal transduction inhibitors, farnesyl transferase inhibitors, antibodies and novel chemotherapeutics. To date, small-molecule inhibitors and targeted therapies have had limited single-agent efficacy and have required combination with chemotherapy. The role of hematopoietic stem cell transplantation in older patients is under investigation. All patients over 60 years of age with acute myeloid leukemia should be encouraged to participate in a clinical trial if possible.

A comparison of low-dose cytarabine and hydroxyurea with or without all-trans retinoic acid for acute myeloid leukemia and high-risk myelodysplastic syndrome in patients not considered fit for intensive treatment

BACKGROUND

The survival of older patients with acute myeloid leukemia has not improved. Few clinical trials have been available for older patients who are not considered fit for an intensive chemotherapy approach.

METHODS

Between December 1998 and November 2003, as part of National Cancer Research Institute Acute Myeloid Leukemia 14 Trial, 217 patients, who were deemed unfit for intensive chemotherapy were randomized to receive low-dose cytarabine (Ara-C) (20 mg twice daily for 10 days) or hydroxyurea with or without all-trans retinoic acid (ATRA).

RESULTS

Low-dose ara-C produced a better remission rate (18% vs 1%; odds ratio [OR], 0.15; 95% confidence interval [95% CI], 0.06-0.37; P = .00006) and better overall survival (OR, 0.60; 95% CI, 0.44-0.81; P = .0009), which was accounted for by the achievement of complete remission (CR) (duration of CR: 80 weeks vs 10 weeks for patients with no CR). Patients who had adverse cytogenetics did not benefit. ATRA had no effect. Toxicity scores or supportive care requirements did not differ between the treatment arms.

CONCLUSIONS

Older, less fit patients have a poor outcome, and few trials have been conducted in this patient group. Low-dose ara-C treatment was superior to best supportive care and hydroxyurea because it had greater success in achieving CR, and it could represent standard care against which new treatments may be compared in this patient group.

Treatment of Older Patients With Acute Myeloid Leukemia—New Agents

The experience of most collaborative study groups is that the outcome for older patients has, unlike in younger patients, failed to improve over the last two decades. In addition there are a substantial number of older patients who do not enter collaborative group trials because they are not considered suitable for an intensive chemotherapy approach. During this era many combinations of chemotherapeutic agents at different dose levels have been tried. It is clear that novel agents and new approaches must be used to improve the situation, and should include options for patients who are not fit for intensive treatment. Fortunately, the increased understanding of the molecular basis and heterogeneity of the disease has fostered the development of novel agents. Chemo-resistance is a key characteristic of acute myeloid leukaemia (AML) in older patients and a number of randomized trials have now been completed to assess this approach. New possibilities of selectively killing leukemic cells and/or modifying toxicity are in prospect with the development of antibody directed chemotherapy in the form of gemtuzumab ozogamicin (Mylotarg; Wyeth, Philadelphia, PA). New drugs such as clofarabine or cloretazine are being evaluated. Molecular mechanisms, whether recognized or not, have been targeted by the use of FLT-3 and farnesyl transferase (FT) inhibitors. With several new agents to evaluate, novel approaches to trial design aimed at detecting options likely to make a useful impact are needed.

Artificial neural network as an alternative to multiple regression analysis in optimizing formulation parameters of cytarabine liposomes

The objective of the study was to optimize the formulation parameters of cytarabine liposomes by using artificial neural networks (ANN) and multiple regression analysis using 3(3) factorial design (FD). As model formulations, 27 formulations were prepared. The formulation variables, drug (cytarabine)/lipid (phosphatidyl choline [PC] and cholesterol [Chol]) molar ratio (X1), PC/Chol in percentage ratio of total lipids (X2), and the volume of hydration medium (X3) were selected as the independent variables; and the percentage drug entrapment (PDE) was selected as the dependent variable. A set of causal factors was used as tutorial data for ANN and fed into a computer. The optimization was performed by minimizing the generalized distance between the predicted values of each response and the optimized one that was obtained individually. In case of 3(3) factorial design, a second-order full-model polynomial equation and a reduced model were established by subjecting the transformed values of independent variables to multiple regression analysis, and contour plots were drawn using the equation. The optimization methods developed by both ANN and FD were validated by preparing another 5 liposomal formulations. The predetermined PDE and the experimental data were compared with predicted data by paired t test, no statistically significant difference was observed. ANN showed less error compared with multiple regression analysis. These findings demonstrate that ANN provides more accurate prediction and is quite useful in the optimization of pharmaceutical formulations when compared with the multiple regression analysis method.

Standard and low-dose chemotherapy for the treatment of myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders with an invariably fatal outcome. Other than bone marrow transplantation, no treatment has been able to alter the natural history of MDS. As a result, there has been an interest in identifying new and more effective chemotherapeutic agents. Many of the drugs that have been evaluated in an attempt to increase remissions and prolong survival were selected because of their activity in acute myeloid leukemia. Thus cytarabine has been the most widely studied drug. Although numerous studies suggested activity for low-dose cytarabine (LoDAC), a careful analysis of the data identified a complete remission (CR) rate of less than 20%, without meaningful clinical benefit. The issue of LoDAC was finally put to rest by a randomized trial in which survival was no better than with supportive care. 5-Azacytidine induces cellular differentiation by hypomethylation of DNA. Phase II trials noted CRs in fewer than 10% of patients, with response rates under 30%, although additional patients appeared to experience hematologic and clinical benefit. A randomized trial of 5-azacytidine versus supportive care failed to demonstrate a survival benefit. One of the most promising new agents is the topoisomerase inhibitor topotecan, which achieves CRs in more than 30% of patients. Combinations of this drug with other active agents are in development. Obviously, new treatment strategies are needed to improve the outcome of MDS patients. Combination approaches incorporating new, active agents should have sound scientific rationale, targeting biological differences among the various MDS subtypes.

Acute nonlymphocytic leukemia with basophilic differentiation and t(9,11)(p22,q23) in a child

A 20-month-old child was treated for acute nonlymphocytic leukemia (ANLL) with basophilic differentiation. His leukemic cells also had the cytogenetic abnormality of t(9,11)(p22,q23). Although immature blasts responded well to induction therapy with etoposide, the leukemic cells that were more differentiated toward basophils were quite refractory to the drug. However, complete remission was finally achieved with a conventional multidrug regimen.

Low-dose cytosine arabinoside in acute non-lymphoblastic leukemia

Eighteen previously untreated patients with acute non-lymphoblastic leukemia (ANLL) were treated with cytosine arabinoside (Ara-C) in low doses (10 mg/m2 every 12 hours) subcutaneously for 3 weeks. Complete remission (CR) was achieved in four patients (22.2%), and myelosuppression was observed in nearly all of them. Thrombocytopenia (20 X 10(3)/microliters) was pronounced in the third week of treatment and six patients (33.3%) needed platelet support. Contrary to earlier claims, our experience suggests that treatment with low-dose Ara-C is associated with significant cytopenias. Ara-C does not obviate the need for intensive supportive care and CR rates are no longer better. Low-dose Ara-C does not seem to be a choice in previously untreated ANLL patients who otherwise have a high probability of achieving a CR with standard multidrug chemotherapy protocols.

Differentiation induction therapy of myelodysplastic syndromes

Myelodysplastic syndromes are a heterogenous group of haemopoietic stem cell disorders characterized by dysplastic haematopoiesis and a defective maturation of a slowly expanding or sometimes of a stable population of haemopoietic progenitors. Defective maturation, which may involve one or more of the marrow cell lineages is regarded as the central pathophysiological feature of myelodysplastic syndromes. Patients with myelodysplastic syndromes respond poorly to conventional cytotoxic chemotherapy, frequently developing a prolonged marrow aplasia. The alternative and more appropriate form of therapy is differentiation induction therapy. The results of few preliminary clinical studies in myelodysplastic patients showed that a combination of differentiating agents is superior to single agent differentiation therapy. An extensive pre-clinical screening of the response of fresh cells from myelodysplastic patients in primary culture is needed to establish the optimal doses and conditions for significant synergies between various differentiating agents followed by large controlled randomized clinical trials based on differentiation induction therapy for patients with myelodysplastic syndromes.

Low dose cytosine arabinoside in refractory anemia with excess of blasts in transformation

Myelodysplastic syndromes (MDS) are heterogeneous diseases. Patients with blast counts of more than 20% of nucleated bone marrow cells have a high risk of short survival. We treated six patients with refractory anemia with excess of blast in transformation (RAEBiT) with low dose cytosine arabinoside (LD Ara-C). We had one partial remission (PR), surviving 16 weeks and two complete remissions (CR), surviving 22 and 55+ months. Myelosuppression was dominant in all patients, but was not as serious as with conventional remission-induction treatments for leukemias. Bone marrow aplasia occurred in all responding patients, but a differentiation effect is possible too. Maintenance therapy with LD Ara-C may be important for the two long-lasting CR.

Use of differentiation-inducing agents in the myelodysplastic syndrome and acute non-lymphocytic leukemia

The use of chemical agents that induce differentiation of malignant cells to normal cells has held great promise as an adjunct to standard chemotherapy. In vitro data has shown that 13-cis-retinoic acid can differentiate certain leukemia cell lines (e.g., HL-60) into stable granulocyte cells. In this study, oral 13-cis-retinoic acid was administered to four patients with the myelodysplastic syndrome (MDS) and to four patients with acute nonlymphocytic leukemia (ANLL). None of the MDS patients showed an hematologic response to the drug, while three of four ANLL patients responded with normalized peripheral blood counts. The side effects of the drug at 80-120 mg/d (dry skin, cheilitis, epistaxis) were self limiting.

Treatment of acute myeloid leukemia in elderly patients. A retrospective study

In an attempt to rationalize the use of therapy in acute myeloblastic leukemia (AML) in elderly patients, 69 cases of primary AML in patients older than 60 years of age were reviewed retrospectively. Therapy was empirical and 12 patients received supportive care (SC) only, 35 received aggressive chemotherapy (AC), and 22 received low-dose cytosine arabinoside (LD-araC). Patients receiving SC only often had a poor Karnofski index and their median survival was 17 days. Aggressive chemotherapy yielded complete remissions (CR) in 48% of the patients, whereas 23% of the patients had resistant disease (RD) and 29% had other failures (OF). Low-dose araC, which was administered to patients significantly older than those receiving AC, yielded 23% CR, 68% RD, and 9% OF, with important hematologic toxicity in most patients. Median survival was 211 days in patients receiving AC and 235 days in patients treated with LD-araC. Survival beyond 2 years from diagnosis was noted in the AC group only. A low Karnofski index was the strongest factor in poor prognosis, while age was not a prognostic factor. The initial characteristics of the patients did not allow us to define groups of patients who should be treated by either AC or LD-araC. We concluded that the decision to treat patients actively should rely more on the patient's general condition and socio-economical criteria than on age.

Review of clinical and haematological response to low-dose cytosine arabinoside in acute myeloid leukaemia

15 patients with acute myeloid leukaemia (AML) were treated with low-dose cytosine arabinoside (LD ARA-C). 2 patients had complete remissions, which lasted for 8 and 3 months, and 5 patients had a partial remission. 46% of the patients thus responded to LD ARA-C. This included 1 responding patient who had not previously responded to therapy with 6-mercaptopurine, thioguanine, or vinblastine. The 2 patients with complete remission did not show LD ARA-C-induced hypoplasia of bone marrow, although 1 had hypoplastic AML before therapy. Leukaemic cells from 1 patient showed in vivo maturation from M1 to M3 after LD ARA-C treatment. The present results, together with the published data, indicate that: a. LD ARA-C treatment, although it may have some toxic effects, is an effective treatment for some patients with AML, especially those with hypoplastic AML; b. Response to LD ARA-C can be obtained after one or several courses of treatment; c. LD ARA-C-induced remissions are sometimes obtained even in patients who fail in more conventional treatments; d. LD ARA-C-induced remissions can be achieved without bone marrow hypoplasia, and induction of hypoplasia by itself does not always result in complete remission; e. LD ARA-C can induce in vivo maturation of leukaemic cells. It is suggested that induction of remission in AML patients by LD ARA-C may result from either differentiation of leukaemic blast cells, cytotoxicity to leukaemic blasts, or both mechanisms acting together.

Low dose ara-C administered by continuous subcutaneous infusion: a pharmacologic evaluation

Low dose ara-C has been widely used in the treatment of preleukemia and leukemia. These studies have generally utilized either a twice daily, subcutaneous bolus schedule or a continuous intravenous infusion schedule. In order to surmount the logistical problems of long term intravenous infusion while providing prolonged ara-C exposure, we have studied the pharmacology of administering ara-C (20 mg/M2/d) by continuous subcutaneous infusion. The results obtained in eight patients demonstrate that steady state plasma ara-C levels achieved during continuous subcutaneous infusion (24.6-65.6 nM) are not significantly different than those obtained during intravenous infusions (26.2-61.5 nM). Subcutaneous infusions result in prolonged myelosuppression similar to that seen with continuous intravenous infusions. The continuous infusion of low dose ara-C by the subcutaneous route provides a treatment option for some outpatients and offers advantages over intravenous infusions which often require placement of venous catheters or hospitalization.