Leukemic transformation of polycythemia vera and essential thrombocythemia possibly associated with an alkylating agent

AML1/RUNX1 point mutation possibly promotes leukemic transformation in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by proliferation of one or more myeloid cell lineages. Some patients exhibit leukemic transformation (LT) by unknown mechanisms, and chemotherapy may increase the risk of LT. To clarify the molecular mechanisms of LT, gene alterations involved in LT from patients in the chronic phase (CP) of MPNs were identified. Among 18 patients who progressed to leukemia, AML1/RUNX1 mutations were detected in 5 patients at the LT but in none at the CP. To investigate the leukemogenic effect of AML1/RUNX1 mutants, the AML1D171N mutant was transduced into CD34+ cells from patients in the CP of MPNs. The D171N transduction resulted in proliferation of immature myeloid cells, enhanced self-renewal capacity, and proliferation of primitive progenitors. Taken together, these results indicate that AML1/RUNX1 point mutations may have a leukemogenic potential in MPN stem cells, and they may promote leukemic transformation in MPN.

Therapy-related patterns of cytogenetic abnormalities in acute myeloid leukemia and myelodysplastic syndrome post polycythemia vera: single center experience and review of literature

A minor fraction of patients with polycythemia vera (PV) develop a terminal acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Analysis of the cytogenetic abnormalities during AML or MDS may help in understanding if this development is part of the natural course of the disease or induced by myelosuppressive therapy. Thirty-six cases with AML or MDS post PV, collected in a single Swedish institution during a 33-year period, are described with special regard to time to development of AML or MDS, therapy given during active PV, and cytogenetic findings during AML or MDS. A further 118 cases of AML or MDS post PV, in whom type of therapy during active PV and cytogenetic findings during AML or MDS were reported, were collected from the literature. AML or MDS developed in our own series after 1-30 years with a fairly constant rate (two cases per year). The most frequent cytogenetic abnormalities were +1q, -5, 5q-, -7, 7q-, +8, +9, 11q-, 13q-, and 20q-. When patients in the total material (n = 154) were divided with regard to treatment during active PV, marked differences were observed. The highest frequency of abnormalities was found in patients given multiple lines of therapy (n = 61), dominating features being -5/5q- in 28 patients (46%), -7/7q- in 19 patients (31%), numerous translocations in 24 patients (39%), and unidentified markers in 22 patients (36%). Half of the patients treated with hydroxyurea alone showed a -5 or 5q- abnormality. In patients treated with phlebotomy alone, +8 and +9 were the most frequent findings. The type of therapy given during active PV influences the type of chromosome abnormalities present during terminal AML or MDS and can also be instrumental in the development of leukemia.

A review of the therapeutic agents used in the management of polycythaemia vera

The acquired clonal disorder Polycythaemia Vera leads to increased erythropoiesis, myelopoiesis and megakaryopoeisis. These anomalies result in an increased incidence of thromboembolic events, transformation to acute leukaemia and myelofibrosis. Treatments which aim to reduce the event rate may increase anaemia but may also affect the rate of complications. This paper reviews the evidence for the treatments which have been used in the management of the disorders over a 50 plus year period. Assessment of this evidence and its limitations form the basis for the current suggested management plans.

[Treatment of essential thrombocythemia]

PURPOSE

Essential thrombocythemia (ET) is a myeloproliferative syndrome that rises many therapeutic problems. This affection is rarely life threatening, but hemorrhagic and thrombotic complications must be prevented when possible. The rarity of these complications makes difficult the assessment of treatment efficiency. Few randomised clinical trials were done, and treatment often rests on retrospective studies. The potential toxicity of treatments, their leukemogenicity in particular, rises a decisional problem for young patients. We propose to review available data in order to propose the most rational treatment for each patient.

CURRENT KNOWLEDGE AND KEY POINTS

After numerous years when we only disposed of retrospective studies, non-randomised prospective studies or isolated case-reports, two randomised trials allows us to more precisely define ET treatment. The first trial proved the efficiency of the hydroxyurea-aspirin association in the prevention of thrombotic events in high-risk patients. The second trial signalled to our attention the increased risk of bleeding of the association anagrelide-aspirin, with also the possibility of increased appearance of myelofibrosis.

FUTURE PROSPECTS AND PROJECTS

New perspectives in the treatment of ET will require to get more insights in the role of hydroxyurea and anagrelide in particular by longer follow-up. But not less important is a better definition of the thrombosis risks (who has to be treated?) and also of the diagnostic groups since ET can, in some particular cases, be misdiagnosed with polycythemia vera or idiopathic myelofibrosis.

Bone marrow histopathology following cytoreductive therapy in chronic idiopathic myelofibrosis

AIMS

To analyse systematically therapy-induced lesions of haematopoiesis in chronic idiopathic myelofibrosis (IMF).

METHODS AND RESULTS

A total of 759 sequential bone marrow (BM) biopsies (median interval 32 months) were performed in 261 patients with IMF. Besides a control group (symptomatic treatment), monotherapies included busulfan, hydroxyurea and interferon. In all therapy groups hypoplasia of varying degree was a frequent finding and often accompanied by a patchy distribution of haematopoiesis. Most conspicuous was gelatinous oedema showing a tendency to develop discrete reticulin fibrosis (scleroedema). Minimal to moderate maturation defects of megakaryopoiesis and erythroid precursors occurred, but overt myelodysplastic features were most prominent following hydroxyurea and busulfan therapy. Acceleration and blastic crisis were characterized by the appearance of immature and CD34+ progenitor cells. Concerning the dynamics of fibrosis, no differences were observed between controls and the various therapy groups. In 143 patients (55%) without or with little reticulin at onset, an increase in myelofibrosis was detectable that progressed to overt collagen fibrosis.

CONCLUSIONS

Therapy-related bone marrow lesions in IMF comprise a strikingly variable spectrum that may include aplasia with scleroedema and a patchy distribution of myelodysplastic haematopoiesis associated with progressive myelofibrosis.

Leukemia and myelodysplasia effect of multiple cytotoxic therapy in essential thrombocythemia

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by increased risk of thrombosis and/or hemorrhages. Cytotoxic drugs are mostly used in patients at high risk for thrombotic complications, while their use is still debated in low risk patients because of the risk of leukemia or secondary neoplasm. We discuss the leukemic risk of available treatment strategies in a large cohort of patients. Over a 12 years period we treated 23 patients with busulfan (BU), 1 with pipobroman (Pi), 6 with 32P, 48 with hydroxyurea (HU) in 62 cases associated with acetyl salicylic acid (ASA) while 77 patients received ASA alone and 33 did not receive any therapy. We observed 2 cases of acute leukemia (AL) and 1 of myelodysplastic syndrome (MDS). One of these patients had been treated with 32P and Pi these after with and the other two with BU and HU. They represented 23% of all patients treated with more than 1 cytotoxic agent, 16.6% of 32P treated subjects, 4% of those with HU and 6.4% of those with BU. The case of MDS occurred in a 81 years old female and represents 4% of cases of ET over the 70 years of age. No cases of AL or MDS were observed in patients not receiving cytotoxic therapy (with or without ASA). According to our experience the use of more than one cytotoxic agent in ET confirms the increase in the risk of leukemia in these cases. However, none of the patients treated with HU alone, even for more than 10 years (12 cases) developed AL. No treatment or therapy with ASA alone may be the best choice in young patients with ET with a low risk of thrombotic complications.

Transition of polycythemia vera to chronic neutrophilic leukemia

Two cases of polycythemia vera (PV) had transition to a hematological condition compatible with chronic neutrophilic leukemia (CNL) 17 and 8 years after diagnosis, respectively. One patient was treated with carboquone followed by hydroxyurea (HU) and the other with HU during PV phase. On transition, both had neutrophilia with white blood cell count above 40,000/microl, elevated neutrophil alkaline phosphatase activity, splenomegaly, normal karyotype without bcr-abl rearrangement. Busulfan was temporally effective in controlling the neutrophil count. However, one patient progressed to the so-called spent phase and the other subsequently had multiple transitions between PV and CNL. These cases may represent a form of uncommon evolution of PV and support the contention that CNL is a type of myeloproliferative disorder and that at least some CNL cases have derangement at the hematopoietic stem cell level.

Acute Myeloid Leukemia and Myelodysplastic Syndromes Following Essential Thrombocythemia Treated With Hydroxyurea: High Proportion of Cases With 17p Deletion

Treatment with alkylating agents or radiophosphorous (32P) has been shown to carry a certain leukemogenic risk in myeloproliferative disorders (MPDs), including essential thrombocytemia (ET). The leukemogenic risk associated to treatment with hydroxyurea in ET, on the other hand, is generally considered to be relatively low. Between 1970 and 1991, we diagnosed ET in 357 patients, who were monitored until 1996. One or several therapeutic agents had been admistered to 326 patients, including hydroxyurea (HU) in 251 (as only treatment in 201), pipobroman in 43, busulfan in 41, and32P in 40. With a median follow-up duration of 98 months, 17 patients (4.5%) had progressed to acute myeloid leukemia (AML; six cases) or myelodysplastic syndrome (MDS; 11 cases). Fourteen of these patients had received HU, as sole treatment in seven cases, and preceded or followed by other treatment in seven cases, mainly pipobroman (five cases). The remaining three leukemic progressions occurred in patients treated with 32P (two cases) and busulfan (one case). The incidence of AML and MDS after treatment, using 32P alone and 32P with other agents, busulfan alone and with other agents, HU alone and with others agents, and pipobroman alone and with other agents was 7% and 9%, 3% and 17%, 3.5% and 14%, and 0% and 16%, respectively. Thirteen of 17 patients who progressed to AML or MDS had successful cytogenetic analysis. Seven of them had rearrangements of chromosome 17 (unbalanced translocation, partial or complete deletion, isochromosome 17q) that resulted in 17p deletion. They also had a typical form of dysgranulopoiesis combining pseudo Pelger Hüet hypolobulation and vacuoles in neutrophils, and p53 mutation, as previously described in AML and MDS with 17p deletion. Those seven patients had all received HU, as the only therapeutic agent in three, and followed by pipobroman in three. The three patients who had received no HU and progressed to AML or MDS had no 17p deletion. A review of the literature found cytogenetic analysis in 35 cases of AML and MDS occurring after ET, 11 of whom had been treated with HU alone. Five of 35 patients had rearrangements that resulted in 17p deletion. Four of them had been treated with HU alone. These results show that treatment with HU alone is associated with a leukemic risk of approximately 3.5%. A high proportion of AML and MDS occurring in ET treated with HU (alone or possibly followed by pipobroman) have morphologic, cytogenetic, and molecular characteristics of the 17p− syndrome. These findings suggest that widespread and prolonged use of HU in ET may have to be reconsidered in some situations, such as asymptomatic ET.

Acute Myeloid Leukemia and Myelodysplastic Syndromes Following Essential Thrombocythemia Treated With Hydroxyurea: High Proportion of Cases With 17p Deletion

Treatment with alkylating agents or radiophosphorous (32P) has been shown to carry a certain leukemogenic risk in myeloproliferative disorders (MPDs), including essential thrombocytemia (ET). The leukemogenic risk associated to treatment with hydroxyurea in ET, on the other hand, is generally considered to be relatively low. Between 1970 and 1991, we diagnosed ET in 357 patients, who were monitored until 1996. One or several therapeutic agents had been admistered to 326 patients, including hydroxyurea (HU) in 251 (as only treatment in 201), pipobroman in 43, busulfan in 41, and32P in 40. With a median follow-up duration of 98 months, 17 patients (4.5%) had progressed to acute myeloid leukemia (AML; six cases) or myelodysplastic syndrome (MDS; 11 cases). Fourteen of these patients had received HU, as sole treatment in seven cases, and preceded or followed by other treatment in seven cases, mainly pipobroman (five cases). The remaining three leukemic progressions occurred in patients treated with 32P (two cases) and busulfan (one case). The incidence of AML and MDS after treatment, using 32P alone and 32P with other agents, busulfan alone and with other agents, HU alone and with others agents, and pipobroman alone and with other agents was 7% and 9%, 3% and 17%, 3.5% and 14%, and 0% and 16%, respectively. Thirteen of 17 patients who progressed to AML or MDS had successful cytogenetic analysis. Seven of them had rearrangements of chromosome 17 (unbalanced translocation, partial or complete deletion, isochromosome 17q) that resulted in 17p deletion. They also had a typical form of dysgranulopoiesis combining pseudo Pelger Hüet hypolobulation and vacuoles in neutrophils, and p53 mutation, as previously described in AML and MDS with 17p deletion. Those seven patients had all received HU, as the only therapeutic agent in three, and followed by pipobroman in three. The three patients who had received no HU and progressed to AML or MDS had no 17p deletion. A review of the literature found cytogenetic analysis in 35 cases of AML and MDS occurring after ET, 11 of whom had been treated with HU alone. Five of 35 patients had rearrangements that resulted in 17p deletion. Four of them had been treated with HU alone. These results show that treatment with HU alone is associated with a leukemic risk of approximately 3.5%. A high proportion of AML and MDS occurring in ET treated with HU (alone or possibly followed by pipobroman) have morphologic, cytogenetic, and molecular characteristics of the 17p− syndrome. These findings suggest that widespread and prolonged use of HU in ET may have to be reconsidered in some situations, such as asymptomatic ET.

A novel myeloid cell line, Marimo, derived from therapy-related acute myeloid leukemia during treatment of essential thrombocythemia: consistent chromosomal abnormalities and temporary C-MYC gene amplification

A novel myeloid leukemia cell line, Marimo, was established from bone marrow cells of a patient with secondary acute myeloid leukemia (AML) that had developed during the treatment of essential thrombocythemia (ET) with busulfan. Karyotype at the ET phase was 46,XX,der(15)t(1;15) (q23;p12-13), but at the blastic phase changed to 44,XX,-5,del(8)(q22), add(17)(p11),+18, psu dic(18;9) (q23;p21) x 2 lacking t(1;15). In Marimo cells, C-MYC gene was temporarily amplified by double-minutes (dmin) but disappeared at 33 months, whereas t(10;14;11)(q22;q32;q13) and t(10;14)(q22;q32) were added in vitro psu dic(18;9) x 2 and add(17)(p11) were consistently found throughout the culture. These results suggest that this AML clone is not derived from ET but rather is therapy-related.

Treatment of Polycythemia Vera: Use of 32P Alone or in Combination With Maintenance Therapy Using Hydroxyurea in 461 Patients Greater Than 65 Years of Age

Despite myelosuppression, polycythemic (PV) patients greater than 65 years of age have a high risk of vascular complications, and the leukemic risk exceeds 15% after 12 years. Is the addition of low-dose maintenance treatment with hydroxyurea (HU) after radiophosphorus (32P) myelosuppression able to decrease these complications? Since the end of 1979, 461 patients were randomized to receive (or not) low-dose HU (5 to 10 mg/kg/d), after the first 32P-induced remission, and were observed until death or June 1996. Maintenance treatment very significantly prolonged the duration of 32P-induced remissions and reduced the annual mean dose received to one-third. However, despite this maintenance, 25% of the patients had an excessive platelet count and the rate of serious vascular complications was not decreased, except in the most severe cases with short-term relapse of polycythemia. Furthermore, the leukemia rate was significantly increased beyond 8 years and a significant excess of carcinomas was also observed. The continuous use of HU did not decrease the risk of progression to myelofibrosis (incidence of 20% after 15 years). Life expectancy was shorter (a median of 9.3 years v 10.9 years with 32P alone), except in the most severe cases (initial 32P-induced remission lasting <2 years) in which maintenance treatment moderately prolonged the survival by reducing the vascular risk. In most cases of PV, in which the duration of the first 32P-induced remission exceeded 2 years, the introduction of HU maintenance did not reduce the vascular risk. Although it considerably decreased the mean dose of 32P received, HU maintenance therapy significantly increased the leukemia and cancer risks and reduced the mean life expectancy by 15%. However, in cases with more rapid recurrence, the introduction of maintenance treatment reduced the vascular risks and moderately prolonged survival. The use of HU as a maintenance therapy is therefore only justified in this situation.

New drugs in essential thrombocythemia and polycythemia vera

Among the chronic myeloproliferative disorders, polycythemia vera and essential thrombocythemia are unique because of their association with thrombohemorrhagic manifestations and their relatively indolent clinical course. Patients with essential thrombocythemia may not have a significant shortening of life-expectancy and most may not require specific therapy. However, patients with polycythemia vera have a significant risk of transformation of polycythemia vera into acute leukemia or postpolycythemic myelofibrosis (or both). 'High-risk-for-thrombosis' patients with either polycythemia vera or essential thrombocythemia require specific therapy with a platelet-lowering agent to prevent thrombotic complications. Currently, the standard agent used for this is hydroxyurea. However, its tetratogenic and leukemogenic potential has been of concern. As a result, new platelet-lowering agents are being evaluated in the treatment of polycythemia vera and essential thrombocythemia. Anagrelide and interferon alfa are two such agents and have been shown to be effective in reducing platelet counts in patients with chronic myeloproliferative disorders. The putative mechanism of action of these drugs, their specific activity in polycythemia vera and essential thrombocythemia, side-effect profile, and current indications are discussed herein.