Negligible clinical effects of thalidomide in patients with myelofibrosis with myeloid metaplasia

Myeloproliferative Neoplasms, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology

The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) consist of myelofibrosis, polycythemia vera, and essential thrombocythemia and are a heterogeneous group of clonal blood disorders characterized by an overproduction of blood cells. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for MPN were developed as a result of meetings convened by a multidisciplinary panel with expertise in MPN, with the goal of providing recommendations for the management of MPN in adults. The Guidelines include recommendations for the diagnostic workup, risk stratification, treatment, and supportive care strategies for the management of myelofibrosis, polycythemia vera, and essential thrombocythemia. Assessment of symptoms at baseline and monitoring of symptom status during the course of treatment is recommended for all patients. This article focuses on the recommendations as outlined in the NCCN Guidelines for the diagnosis of MPN and the risk stratification, management, and supportive care relevant to MF.

Ruxolitinib for myelofibrosis

The aim of the present study was to assess the beneficial and harmful effects of ruxolitinib in patients with myelofibrosis (MF). The Cochrane databases, PubMed and Embase were searched for studies published up to October 2012. Randomised controlled trials assessing ruxolitinib versus a placebo or the best available therapy in patients with MF were included. Two trials randomised 528 patients with MF to ruxolitinib versus a placebo or ruxolitinib versus the best available therapy. Compared with the placebo, ruxolitinib had a significant beneficial effect on the proportion of patients that had a reduction in spleen volume of ≥35% at 24 weeks [odds ratio (OR), 109.78; 95% confidence interval (CI), 14.97–804.78] or an increased overall survival rate (OR, 2.02; 95% CI, 0.99–4.12). Ruxolitinib significantly increased the risk of several non-haematological or haematological adverse events, but not the risk of treatment discontinuations (OR, 1.04; 95% CI, 0.50–2.14). Compared with the best available therapy, ruxolitinib had a significant beneficial effect on the proportion of patients that had a reduction in spleen volume of ≥35% at 24 (OR, 68.45; 95% CI, 4.15–1129.19) or 48 weeks (OR, 56.20; 95%CI, 3.40–928.67). Ruxolitinib once again significantly increased the risk of several non-haematological adverse events, serious adverse events and dose reductions or interruptions (OR, 9.60; 95% CI, 4.66–19.81), but not the risk of treatment discontinuations (OR, 1.54; 95% CI, 0.48–4.97). In conclusion, based on the trials included in the present study, the use of ruxolitinib is beneficial in the treatment of MF.

Patterns of survival among patients with myeloproliferative neoplasms diagnosed in Sweden from 1973 to 2008: a population-based study

PURPOSE

Reported survival in patients with myeloproliferative neoplasms (MPNs) shows great variation. Patients with primary myelofibrosis (PMF) have substantially reduced life expectancy, whereas patients with polycythemia vera (PV) and essential thrombocythemia (ET) have moderately reduced survival in most, but not all, studies. We conducted a large population-based study to establish patterns of survival in more than 9,000 patients with MPNs.

PATIENTS AND METHODS

We identified 9,384 patients with MPNs (from the Swedish Cancer Register) diagnosed from 1973 to 2008 (divided into four calendar periods) with follow-up to 2009. Relative survival ratios (RSRs) and excess mortality rate ratios were computed as measures of survival.

RESULTS

Patient survival was considerably lower in all MPN subtypes compared with expected survival in the general population, reflected in 10-year RSRs of 0.64 (95% CI, 0.62 to 0.67) in patients with PV, 0.68 (95% CI, 0.64 to 0.71) in those with ET, and 0.21 (95% CI, 0.18 to 0.25) in those with PMF. Excess mortality was observed in patients with any MPN subtype during all four calendar periods (P < .001). Survival improved significantly over time (P < .001); however, the improvement was less pronounced after the year 2000 and was confined to patients with PV and ET.

CONCLUSION

We found patients with any MPN subtype to have significantly reduced life expectancy compared with the general population. The improvement over time is most likely explained by better overall clinical management of patients with MPN. The decreased life expectancy even in the most recent calendar period emphasizes the need for new treatment options for these patients.

Ruxolitinib for the treatment of myelofibrosis: its clinical potential

Ruxolitinib is an orally bioavailable, selective Janus kinase (JAK) 1 and 2 inhibitor approved for the treatment of myelofibrosis (MF), a bone marrow disease in which the JAK pathway is dysregulated, leading to impaired hematopoiesis and immune function. By inhibiting JAK1 and JAK2, ruxolitinib modulates cytokine-stimulated intracellular signaling. In a phase II clinical trial in patients with MF, ruxolitinib recipients exhibited durable reductions in spleen size, reductions in circulating pro-inflammatory cytokines, improvements in physical activity, weight gain, and alleviation of symptoms (including constitutional symptoms) in patients with and without JAK2 mutation. These findings were confirmed by two phase III clinical MF studies, in which a greater proportion of ruxolitinib recipients achieved a spleen volume reduction of ≥35% from baseline at week 24, compared with placebo in one study (41.9% versus 0.7%; P < 0.0001) and with best available therapy in the other (31.9% versus 0%; P < 0.0001). Alleviation of MF symptoms and improvements in quality of life were also significantly greater in ruxolitinib recipients. Overall survival of patients treated with ruxolitinib was significantly longer than of those receiving the placebo. Owing to risks of potentially serious adverse effects, eg, myelosuppression, ruxolitinib should be used under close physician supervision. Longer follow-up of the phase III MF studies is needed to reach firm conclusions regarding ruxolitinib’s capacity to modify the natural disease course.

How I treat splenomegaly in myelofibrosis

Symptomatic splenomegaly, a frequent manifestation of myelofibrosis (MF), represents a therapeutic challenge. It is frequently accompanied by constitutional symptoms and by anemia or other cytopenias, which make treatment difficult, as the latter are often worsened by most current therapies. Cytoreductive treatment, usually hydroxyurea, is the first-line therapy, being effective in around 40% of the patients, although the effect is often short lived. The immunomodulatory drugs, such as thalidomide or lenalidomide, rarely show a substantial activity in reducing the splenomegaly. Splenectomy can be considered in patients refractory to drug treatment, but the procedure involves substantial morbidity as well as a certain mortality risk and, therefore, patient selection is important. For patients not eligible for splenectomy, transient relief of the symptoms can be obtained with local radiotherapy that, in turn, can induce severe and long-lasting cytopenias. Allogeneic hemopoietic stem cell transplantation is the only treatment with the potential for curing MF but, due to its associated morbidity and mortality, is usually restricted to a minority of patients with poor risk features. A new class of drugs, the JAK2 inhibitors, although also palliative, are promising in the splenomegaly of MF and will probably change the therapeutic algorithm of this disease.

New drugs for the treatment of myelofibrosis

Managing patients with myelofibrosis (MF)-either those with primary MF or those whose MF has evolved from antecedent polycythemia vera or essential thrombocythemia-presents many challenges to the hematologist. Cure is potentially achievable through allogeneic stem cell transplantation, but this therapy is either inappropriate or not feasible for most patients. MF patients suffer from a range of debilitating disease manifestations (eg, massive splenomegaly, cytopenias, constitutional symptoms, and transformation to a treatment-refractory blast phase). Currently available therapies are palliative but can be of significant value to some MF patients for anemia, splenomegaly, or sometimes both manifestations. New medical therapies for MF revolve around three main themes: immunomodulation (to assist anemia), hypomethylation strategies, and (the most robust pipeline) the use of targeted JAK2 inhibitors. These latter agents have shown the ability to improve MF-associated splenomegaly and MF-associated symptoms but do not improve (and may exacerbate) anemia or thrombocytopenia. Future targeted agents, and perhaps combinations of agents that currently show complementary benefits, are anticipated to further enhance the efficacy of medical therapy for MF.

Ex vivo activity of thalidomide in childhood acute leukemia

Thalidomide is a drug with anti-angiogenic, anti-inflammatory, immunomodulatory and anti-cancer properties that were found to inhibit the production of TNF-alpha in vitro, stimulate reactive oxygen species production, and inhibit VEGFR in acute leukemias. Ex vivo activity of thalidomide as a single agent and in combination with prednisolone or cytarabine in childhood acute leukemias was analyzed. Forty samples of childhood acute lymphoblastic leukemia (ALL) and 13 acute myeloid leukemia (AML) were tested for cytotoxicity by the MTT assay and cell cycle phases by flow cytometry. Control studies were performed on 9 samples of normal lymphocytes and 4 cell lines. A weak anti-leukemic activity of thalidomide against childhood leukemic samples was observed. However, in the presence of thalidomide, cytotoxicity of prednisolone or cytarabine, increased 3.3-fold and 2.7-fold, respectively, in childhood ALL but was not changed in AML. Thalidomide increased apoptosis in lymphoblasts, and modulated cell cycle arrest caused by prednisolone but not cytarabine in childhood acute lymphoblastic leukemia samples. Thalidomide potentiated ex vivo sensitivity of childhood ALL cells to prednisolone and cytarabine, while no sensitization effect was observed in AML cells.

PTK787/ZK 222584, a small molecule tyrosine kinase receptor inhibitor of vascular endothelial growth factor (VEGF), has modest activity in myelofibrosis with myeloid metaplasia

Angiogenesis is part of the pathophysiology of myelofibrosis with myeloid metaplasia (MMM). PTK787/ZK 222584 (PTK/ZK) is a novel inhibitor of vascular endothelial growth factor receptors. Twenty-nine patients with MMM received a continuous dosing schedule of PTK/ZK doses of 500 or 750 mg twice daily (BID). Transient potentially PTK/ZK related mild nausea, vomiting, dizziness, fatigue, thrombocytopenia, or anorexia occurred in 15% of patients. Dose limiting toxicities of dyspepsia, proteinurea, and/or mucositis were observed in patients treated with 750 mg BID. One (3%) and five (17%) patients achieved complete remission and clinical improvement, respectively. PTK/ZK has modest activity in patients with MMM.

Advances in the therapy of chronic idiopathic myelofibrosis

The molecular basis of chronic idiopathic myelofibrosis (CIMF) has remained elusive, thus hampering the development of effective targeted therapies. However, significant progress regarding the molecular mechanisms involved in the pathogenes is of this disease has been made in recent years that will likely provide ample opportunity for the investigation of novel therapeutic approaches. At the fore front of these advances is the discovery that 35%-55% of patients with CIMF harbor mutations in the Janus kinase 2 tyrosine kinase gene. Until very recently, the management of patients with CIMF involved the use of supportive measures, including growth factors, transfusions, or interferon, and the administration of cyto-reductive agents, such as hydroxyurea and anagrelide. However, several trials have demonstrated the efficacy of antiangiogenic agents alone or in combination with corticosteroids. In addition, the use of reduced-intensity conditioning allogeneic stem cell transplantation has resulted in prolonged survival and lower transplant-related mortality.

Myelofibrosis with myeloid metaplasia: disease overview and non-transplant treatment options

Myelofibrosis with myeloid metaplasia (MMM) is currently classified as a classic (i.e. not yet molecularly defined) myeloproliferative disorder (MPD), along with essential thrombocythemia (ET) and polycythemia vera (PV). All three MPDs represent stem-cell-derived clonal myeloproliferation that, in the case of MMM, is accompanied by an intense bone marrow stromal reaction that includes collagen fibrosis, osteosclerosis, and angiogenesis. To date, both the molecular basis of the primary clonal process and the pathogenetic mechanisms that underlie the secondary histological changes remain elusive. Clinically, MMM is characterized by anemia, multi-organ extramedullary hematopoiesis that often involves the spleen and liver, constitutional symptoms, and premature death from either leukemic transformation or other disease complications. Current diagnosis is based on characteristic but not diagnostic bone marrow histological features. Modern therapy remains palliative but allogeneic stem cell transplantation might be curative to a selected group of patients. This chapter reviews both the old and the new therapy with regard to non-transplant treatment options for MMM.

Phase I and pharmacokinetic study of oral thalidomide in patients with advanced hepatocellular carcinoma

PURPOSE

To evaluate the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), and pharmacokinetics of thalidomide in patients with advanced hepatocellular carcinoma (HCC).

METHODS

Patients with advanced HCC who were not feasible for definitive local therapy were eligible. Patients were enrolled in a cohort of three to receive thalidomide twice daily for 1 week to determine the MTD. Intra-patient dose escalation was permitted. Pharmacokinetic studies were performed at the first dose level and repeated at the second dose level of each patient.

RESULTS

Fifteen patients were accrued at four dose levels with the starting dose range 100-400 mg/day. Two patients at 400 mg/day experienced DLT (grade 3 angioedema and dyspnea, respectively). The MTD of twice-daily schedule was determined as 300 mg/day. The mean steady-state maximal blood concentration and mean steady-state area under the curve had a trend toward positive correlation, but non-linear proportionate, to the daily dose of thalidomide. Pharmacokinetic parameters are comparable for patients of Child-Pugh's A and B. Apparent mild, transient drug-induced transaminitis was early onset, self-limited, which occurred in 30.7% of patients. Serum hepatitis B or C viral titers was largely not affected.

CONCLUSION

The absorption and elimination of thalidomide are not significantly different in HCC patients with compensated or decompensated hepatic dysfunction.

Thalidomide therapy for myelofibrosis with myeloid metaplasia

BACKGROUND

Thalidomide is a putative antiangiogenesis agent with activity in several hematologic malignancies.

METHODS

Forty-four patients who had myelofibrosis with myeloid metaplasia received treatment with thalidomide in a Phase II clinical trial at a dose of 200 mg daily with escalation by 200 mg weekly until the best tolerated dose (maximum, 800 mg) was reached.

RESULTS

Seventeen of 41 evaluable patients (41%) who received treatment for at least 15 days had a response. A complete response (without reversal of bone marrow fibrosis) was achieved in 4 patients (10%), a partial response was achieved in 4 patients (10%), and hematologic improvements in anemia, thrombopenia, and/or splenomegaly were observed in 9 patients (21%). Improvements in anemia occurred in 7 of 35 patients (20%) with hemoglobin levels <10.0 g/dL, and improvements in thrombopenia occurred in 5 of 24 patients (21%) with platelet counts <100 x 10(9)/L. Five of 24 patients (21%) became transfusion-independent. Major or minor regression of splenomegaly was noted in 9 of 29 evaluable patients (31%), and complete regression was noted in 5 patients. Responders had a lower baseline median vascular endothelial growth factor levels (77.9 pg/mL vs. 97.7 pg/mL; P <.01) and higher median basis fibroblast growth factor levels (60.8 pg/mL vs. 37.4 pg/mL; P <.01) compared with nonresponders. Nine patients (22%) had deterioration that was attributed to thalidomide (resolved after withdrawal) with either progressive cytopenias or excessive proliferation. Two patients developed Grade 3 neutropenia with recovery and resumed therapy with dose reductions, and both later achieved a complete response. Dose-related toxicities included fatigue (50%), constipation (48%), rash or pruritus (37%), sedation (35%), peripheral edema (29%), tremors (23%), peripheral neuropathy (22%), and orthostasis (16%).

CONCLUSIONS

Thalidomide warrants further evaluation in patients with MMM, particularly in combination regimens, along with the investigation of newer analogs.

Future directions in haematology: beyond multiple myeloma

Thalidomide acts on the microenvironment of myelodysplastic syndromes (MDS) by influencing cytokine networks, and growing evidence supports thalidomide's usefulness in the management of haematological malignancies, such as MDS. The European Collaboration Group on Myelofibrosis with Myeloid Metaplasia reviewed patients who received at least four weeks' thalidomide treatment, in doses ranging from 50 mg/day to 400 mg/day. The results showed that 30% of patients had increases in haemoglobin, and, of these, almost 40% became transfusion independent. Platelets were increased in a significant proportion of patients, and approximately 40% of patients had a reduction in their spleen size. Data on thalidomide and acute myeloblastic leukaemia (AML) are conflicting: a recently published study indicated that thalidomide does not have a role in the management of acute myeloblastic leukaemia (AML), while other studies suggest some patients may respond because of thalidomide's ability to activate natural killer cells and cytotoxic T-lymphocytes. Partial responses to thalidomide treatment have been recorded in patients with lymphoma. In a phase II study to assess the activity of thalidomide in patients with Waldenstrom's macroglobulinaemia, a partial response was seen in 25% of patients who received a starting dose of 200 mg, which was escalated in 200 mg increments every 14 days as tolerated to a maximum of 600 mg. Although further study is required, thalidomide shows promise in the treatment of a number of haematological malignancies, many of which currently have limited treatment options and poor prognosis.

bcr/abl-negative, classic myeloproliferative disorders: diagnosis and treatment

Essential thrombocythemia, polycythemia vera, and myelofibrosis with myeloid metaplasia constitute the "classic" bcr/abl-negative myeloproliferative disorders (MPDs). Each of these MPDs represents a stem cell-derived clonal myeloproliferation with the respective features of thrombocytosis, erythrocytosis, and bone marrow fibrosis. Unlike with cases of chronic myeloid leukemia, in which the bcr/abl mutation is invariably detected, current diagnosis of essential thrombocythemia, polycythemia vera, and myelofibrosis with myeloid metaplasia is based on a consensus-driven set of clinical and laboratory criteria that have undergone substantial modification in recent times. The recent discovery of a recurrent activating Janus tyrosine kinase (JAK2) mutation (JAK2VG17F) in all 3 classic MPDs offers another opportunity for refining current diagnoses and disease classifications. In this article, we outline contemporary diagnostic algorithms for each of these disorders and provide an evidence-based approach to management.

Thalidomide : mécanismes d'action et indications en hématologie

Purpose. - Thalidomide, a major teratogen drug, was rehabilitated mainly in malignant hemopathy. Current knowledge and key points. - Thalidomide-mechanisms of action are well known, multiple, they combine immunomodulatory, antiangiogenic properties, and the modulation of cytokines, particularly tumour necrosis factor-alpha. Multiple trials are ongoing, however, the main indication remain multiple myeloma with a response rate of 30% in relapsed patients. Future prospects and projects. - New structural analogues of the thalidomide which priviligiate some of the thalidomide-specific mechanisms of action, the selected cytokine inhibitory drugs (SelCIDS) and the immunomodulatory drugs (IMiDs) family are under evaluation. The IMiDs, which mechanism is based on stimulation of T lymphopoiesis rather than inhibition of tumour necrosis factor-alpha, are under clinical trials in multiple myeloma with interesting results.

New approaches in the treatment of myelofibrosis

Myelofibrosis with myeloid metaplasia (MMM) is a chronic clonal neoangiogenesis disorder characterized by bone marrow fibrosis and neoangiogensis with extramedullary hematopoiesis. Identification of prognostic factors associated with MMM have not impacted the treatment of the disease, which continues to be palliative with the exception of allogeneic stem cell transplantation (SCT) for potential long-term disease-free survival in selected patients. Additional insights into the pathophysiology of MMM have resulted in the use of novel therapeutic strategies in the treatment of this disease. The rationale for the investigation of these agents in MMM and the status of clinical trials with various modalities such as angiogenesis inhibitors (e.g., thalidomide), tyrosine kinase inhibitors (e.g., imatinib mesylate), farnesyl transferase inhibitors (e.g., R115777), and other agents are reviewed, in addition to the potential roles of autologous and allogeneic SCT.

Durable responses to thalidomide-based drug therapy for myelofibrosis with myeloid metaplasia

OBJECTIVE

To present the results of a long-term analysis of 2 sequential phase 2 trials of thalidomide (alone or in combination) for palliation of myelofibrosis with myeloid metaplasia (MMM).

PATIENTS AND METHODS

We analyzed (March 1999 to August 2003) initial and long-term outcomes from 36 patients with symptomatic MMM who had enrolled in either our thalidomide single-agent trial (n=15) or our trial of low-dose thalidomide (50 mg/d) combined with prednisone (n=21).

RESULTS

Among the 36 study patients, 20 (56%) showed some improvement in their clinical course. Response rates for specific end points included improvements in anemia (15 of 36 [42%]), thrombocytopenia (10 of 13 [77%]), or splenomegaly (5 of 30 [17%]). The combination of low-dose thalidomide and prednisone, as opposed to single-agent thalidomide, was better tolerated and more efficacious. After a median follow-up of 25 months (range, 20-56 months), 10 of 36 patients (28%) showed an ongoing response, including 8 patients in whom protocol treatment has been discontinued for a median of 21 months (range, 16-31 months). Durable treatment responses were documented for only anemia and thrombocytopenia. Treatment response was not affected by the baseline status of bone marrow fibrosis, angiogenesis, osteosclerosis, cytogenetics, or circulating myeloid progenitor (CD34) cell count. Unusual drug effects, all reversible, included leukocytosis (8 patients) and/or thrombocytosis (6 patients).

CONCLUSIONS

Thalidomide (alone or combined with prednisone) is an effective first-line treatment of symptomatic anemia or thrombocytopenia in MMM. Thalidomide-based therapy has the potential to produce durable responses in MMM-associated cytopenias, even after discontinuation of the drug.

Thalidomide: Current Role in the Treatment of Non-Plasma Cell Malignancies

Thalidomide, initially introduced as a sedative, was withdrawn from the market in the early 1960s after it was found to be a teratogen. However, it later found use as an investigational agent in the treatment of erythema nodosum leprosum, oral ulcers, graft versus host disease, and wasting associated with the human immunodeficiency syndrome. Its antiangiogenic properties were recognized in the early 1990s during a period where the importance of angiogenesis became increasingly apparent as a critical step in the in the proliferation and spread of malignant neoplasms. This led to the evaluation of thalidomide as an antiangiogenic agent in the treatment of several cancers. Thalidomide has already become part of standard therapy for the treatment of patients with relapsed and refractory multiple myeloma. It has also been found to have varying degree of benefit in various other malignancies. Although more clinical trials are needed, Kaposi's sarcoma and myelofibrosis represent other malignancies in which thalidomide has already demonstrated promising activity. The mechanism of action of thalidomide in cancer is still unclear, but do appear to be mediated by several other mechanisms in addition to its anti-angiogenic properties. This article reviews the current status of thalidomide for the treatment of non-plasma-cell malignancies.

Transplant strategies for idiopathic myelofibrosis

Idiopathic myelofibrosis (IMF) is a clonal stem cell disorder and is one of the four major myeloproliferative disorders, which include essential thrombocythemia (ET), polycythemia vera (PV), and chronic myelogenous leukemia (CML). Patients may be asymptomatic at the early stages, but later progress to marrow fibrosis, splenomegaly with pancytopenia leading to anemia, and other constitutional symptoms. Most of the care available is supportive and only palliates the constitutional symptoms. Prognosis for these patients is dependent on karyotype, hemoglobin count, and age. Stem cell transplantation is the only curative therapy, which results in eradication of the stem cell clone, with the cessation of extramedullary hematopoiesis and resolution of marrow fibrosis and its sequelae. Stem cell replacement therapy using either autologous or allogeneic stem cells has been attempted in small populations of patients with variable benefit. A nonmyeloablative approach has shown promise in a very small number of patients, but additional investigation is required for the ideal management of these patients.

Low-dose thalidomide ameliorates cytopenias and splenomegaly in myelofibrosis with myeloid metaplasia: a phase II trial

PURPOSE

A phase II dose-escalation trial was conducted to ascertain low-dose thalidomide safety and response in patients with advanced myelofibrosis with myeloid metaplasia (MMM).

PATIENTS AND METHODS

Thalidomide was administered together with current therapy to 63 patients, starting at 50 mg daily and increasing to 400 mg as tolerated.

RESULTS

Half of the patients sustained daily doses more than 100 mg and the drop-out rate was 51% at 6 months: the drop-out rate was lower in patients with high baseline fatigue score. At efficacy analysis, anemia was ameliorated in 22% of the patients and transfusions were eliminated in 39% of transfusion-dependent patients. Platelet count increased by 50 x 10(9)/L or more in 22% of patients with an initial count lower than 100 x 10(9)/L. Splenomegaly decreased by more than 50% of the initial size in 19% of patients. Reduction of an overall disease severity score occurred in 31% of patients and was associated with a significant reduction of fatigue. Disease severity amelioration was independently predicted by a high baseline myeloproliferative index (ie, large splenomegaly, thrombocytosis, or leukocytosis).

CONCLUSION

Low-dose thalidomide displays an acceptable toxicity profile and provides an objective and subjective advantage to a relevant portion of MMM patients.

Chronic Myelogenous Leukemia and Myeloproliferative Disease

In Section I, Dr. Stephen O’Brien reviews the latest data on the clinical use of imatinib (STI571, Gleevec, Glivec) in CML. His review focuses on the use of imatinib in newly diagnosed chronic phase patients and summarizes cytogenetic and molecular response data, as well as use of the agent at high doses and in combination with other drugs. A brief summary of the prospective international Phase III studies that are currently ongoing is also provided, and the issues of resistance and definition of suboptimal therapeutic response are also covered. Finally, therapeutic decision-making and treatment strategy are considered.

In Section II, Dr. Ayalew Tefferi considers the latest developments in the biology and therapy of myeloid metaplasia/myelofibrosis. Dr. Tefferi covers what is currently understood of the biology of the disease and reviews established therapies for the condition as well as novel agents that are being used in clinical trials. The development of optimal management strategies for the disease is considered.

In Section III, Dr. Peter Valent reviews the classification of mast cell proliferative disorders and covers the clinical and pathological presentation of this group of neoplasms. He reviews the state-of-the-art regarding the molecular biology of mastocytosis along with diagnostic criteria and novel treatment concepts.

Thalidomide for the treatment of idiopathic myelofibrosis

Except rare instances of allogeneic stem cell transplantation, treatment of idiopathic myelofibrosis (IMF) is only palliative and based on cytostatic treatment (hydroxyurea and anagrelide), androgen therapy, steroids and splenectomy. Thalidomide is an anti-angiogenic and immunomodulatory drug with a wide spectrum of activities, which are not clearly understood. Current data suggest that the action of thalidomide is related to several different mechanisms, including suppression of tumor necrosis factor, effects on basic fibroblast growth factor, vascular endothelial growth factor, interleukins and interferons, downregulation of selected cell surface adhesion molecules, and changes in the lymphocyte subsets. We administered thalidomide to 16 patients with IMF (15 men, one women) who had transfusion-dependent anemia, thrombocytopenia or symptomatic splenomegaly. Median age was 59 yr (range: 52-78). Patients received thalidomide at an escalating dose from 100 to 400 mg/d (median 300 mg). The drug was discontinued in four patients because of progressive disease (two) or polyneuropathy (two). Other adverse effects were obstipation (10), fatigue (eight) and edema (two). Clinical response has now been observed for a median duration of 9 months (range: 3-20). Fifteen patients are evaluable. Anemia improved in six of 10 patients who were anemic. Platelet counts improved in five of seven patients with thrombocytopenia. Splenomegaly regressed in three of 13 patients. Lactate dehydrogenase (LDH) decreased in seven of 12 patients, but increased in four patients. LDH levels were not correlated with clinical response. In summary, thalidomide appears useful in the treatment of IMF.

A phase 2 trial of combination low-dose thalidomide and prednisone for the treatment of myelofibrosis with myeloid metaplasia

Single-agent thalidomide (THAL) at "conventional" doses (> 100 mg/d) has been evaluated in myelofibrosis with myeloid metaplasia (MMM) based on its antiangiogenic properties and the prominent neoangiogenesis that occurs in MMM. THAL monotherapy at such doses produces approximately a 20% response rate in anemia but is poorly tolerated (an adverse dropout rate of > 50% in 3 months). To improve efficacy and tolerability, we prospectively treated 21 symptomatic patients (hemoglobin level < 10 g/dL or symptomatic splenomegaly) with MMM with low-dose THAL (50 mg/d) along with a 3-month oral prednisone (PRED) taper (beginning at 0.5 mg/kg/d). THAL-PRED was well tolerated in all enrolled patients, with 20 patients (95%) able to complete 3 months of treatment. An objective clinical response was demonstrated in 13 (62%) patients, all improvements in anemia. Among 10 patients who were dependent on erythrocyte transfusions, 7 (70%) improved and 4 (40%) became transfusion independent. Among 8 patients with thrombocytopenia (platelet count < 100 x 10(9)/L), 6 (75%) experienced a 50% or higher increase in their platelet count. In 4 of 21 patients (19%), spleen size decreased by more than 50%. Responses observed were mostly durable after discontinuation of the PRED. The dose of THAL in this study (50 mg/d) was better tolerated than the higher doses used in previous studies. Adverse events associated with corticosteroid therapy were mild and transient. Clinical responses did not correlate with improvements in either intramedullary fibrosis or angiogenesis. THAL-PRED is well tolerated and preliminarily appears to be a promising drug regimen for treating cytopenias in patients with MMM.

Chronic myeloproliferative disorders

The Philadelphia chromosome-negative chronic myeloproliferative disorders (CMPD), polycythemia vera (PV), essential thrombocythemia (ET) and chronic idiopathic myelofibrosis (IMF), have overlapping clinical features but exhibit different natural histories and different therapeutic requirements. Phenotypic mimicry amongst these disorders and between them and nonclonal hematopoietic disorders, lack of clonal diagnostic markers, lack of understanding of their molecular basis and paucity of controlled, prospective therapeutic trials have made the diagnosis and management of PV, ET and IMF difficult. In Section I, Dr. Jerry Spivak introduces current clinical controversies involving the CMPD, in particular the diagnostic challenges. Two new molecular assays may prove useful in the diagnosis and classification of CMPD. In 2000, the overexpression in PV granulocytes of the mRNA for the neutrophil antigen NBI/CD177, a member of the uPAR/Ly6/CD59 family of plasma membrane proteins, was documented. Overexpression of PRV-1 mRNA appeared to be specific for PV since it was not observed in secondary erythrocytosis. At this time, it appears that overexpression of granulocyte PRV-1 in the presence of an elevated red cell mass supports a diagnosis of PV; absence of PRV-1 expression, however, should not be grounds for excluding PV as a diagnostic possibility. Impaired expression of Mpl, the receptor for thrombopoietin, in platelets and megakaryocytes has been first described in PV, but it has also been observed in some patients with ET and IMF. The biologic basis appears to be either alternative splicing of Mpl mRNA or a single nucleotide polymorphism, both of which involve Mpl exon 2 and both of which lead to impaired posttranslational glycosylation and a dominant negative effect on normal Mpl expression. To date, no Mpl DNA structural abnormality or mutation has been identified in PV, ET or IMF. In Section II, Dr. Tiziano Barbui reviews the best clinical evidence for treatment strategy design in PV and ET. Current recommendations for cytoreductive therapy in PV are still largely similar to those at the end of the PVSG era. Phlebotomy to reduce the red cell mass and keep it at a safe level (hematocrit < 45%) remains the cornerstone of treatment. Venesection is an effective and safe therapy and previous concerns about potential side effects, including severe iron deficiency and an increased tendency to thrombosis or myelofibrosis, were erroneous. Many patients require no other therapy for many years. For others, however, poor compliance to phlebotomy or progressive myeloproliferation, as indicated by increasing splenomegaly or very high leukocyte or platelet counts, may call for the introduction of cytoreductive drugs. In ET, the therapeutic trade-off between reducing thrombotic events and increasing the risk of leukemia with the use of cytoreductive drugs should be approached by patient risk stratification. Thrombotic deaths seem very rare in low-risk ET subjects and there are no data indicating that fatalities can be prevented by starting cytoreductive drugs early. Therefore, withholding chemotherapy might be justifiable in young, asymptomatic ET patients with a platelet count below 1500000/mm(3) and with no additional risk factors for thrombosis. If cardiovascular risk factors together with ET are identified (smoking, obesity, hypertension, hyperlipidemia) it is wise to consider platelet-lowering agents on an individual basis. In Section III, Dr. Gianni Tognoni discusses the role of aspirin therapy in PV based on the recently completed European Collaboration on Low-dose Aspirin in Polycythemia Vera (ECLAP) Study, a multi-country, multicenter project aimed at describing the natural history of PV as well as the efficacy of low-dose aspirin. Aspirin treatment lowered the risk of cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke (relative risk 0.41 [95% CI 0.15-1.15], P =.0912). Total and cardiovascular mortality were also reduced by 46% and 59%, respectively. Major bleedings were slightly increased nonsignificnsignificantly by aspirin (relative risk 1.62, 95% CI 0.27-9.71). In Section IV, Dr. Giovanni Barosi reviews our current understanding of the pathophysiology of IMF and, in particular, the contributions of anomalous megakaryocyte proliferation, neoangiogenesis and abnormal CD34(+) stem cell trafficking to disease pathogenesis. The role of newer therapies, such as low-conditioning stem cell transplantation and thalidomide, is discussed in the context of a general treatment strategy for IMF. The results of a Phase II trial of low-dose thalidomide as a single agent in 63 patients with myelofibrosis with meloid metaplasia (MMM) using a dose-escalation design and an overall low dose of the drug (The European Collaboration on MMM) will be presented. Considering only patients who completed 4 weeks of treatment, 31% had a response: this was mostly due to a beneficial effect of thalidomide on patients with transfusion dependent anemia, 39% of whom abolished transfusions, patients with moderate to severe thrombocytopenia, 28% of whom increased their platelet count by more than 50 x 10(9)/L, and patients with the largest splenomegalies, 42% of whom reduced spleen size of more than 2 cm.