Myelodysplastic Syndrome

Myelodysplastic Syndrome (MDS): Practice Essentials, Pathophysiology, Etiology

Practice Essentials

Myelodysplastic syndrome (MDS) refers to a heterogeneous group of closely related clonal hematopoietic disorders commonly found in the aging population. All are characterized by one or more peripheral blood cytopenias. Bone marrow is usually hypercellular, but rarely, a hypocellular marrow mimicking aplastic anemia may be seen. Bone marrow cells display aberrant morphology and maturation (dysmyelopoiesis), resulting in ineffective blood cell production.

MDS affects hematopoiesis at the stem cell level, as indicated by cytogenetic abnormalities, molecular mutations, and morphologic and physiologic abnormalities in maturation and differentiation of one or more of the hematopoietic cell lines. [1, 2, 3] See the image below.

Blood film (1000× magnification) demonstrating a v

Blood film (1000× magnification) demonstrating a vacuolated blast in a refractory anemia with excess of blasts in transformation. Courtesy of U. Woermann, MD, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland.

See Myelodysplastic Syndromes: Classification, Features, Diagnosis, and Treatment Options, a Critical Images slideshow, to help identify, classify, work up, and treat these disorders.

MDS may involve one, two, or all three myeloid hematopoiesis cell lineages—erythrocytic, granulocytic, megakaryocytic—depending on the subtype and stage of the disease. The heterogeneity of MDS reflects the fact that its course involves a series of cytogenetic events. In a subgroup of patients, the acquisition of additional genetic abnormalities results in the transformation of MDS into acute myeloid leukemia (AML). Thus, although MDS is clonal, it is considered a premalignant condition.

Patients with MDS may present with clinical manifestations of anemia, thrombocytopenia, and/or neutropenia (see Presentation). The workup in patients with possible MDS includes a complete blood count with differential, peripheral blood smear, and bone marrow studies (see Workup).

Standard care for MDS is constantly changing, but it typically includes supportive therapy, including transfusions, and may include bone marrow stimulation and cytotoxic chemotherapy. Bone marrow transplantation has a limited role. (See Treatment.)

For discussion of MDS in children, see Pediatric Myelodysplastic Syndrome.

Pathophysiology

MDS develops when a clonal mutation predominates in the bone marrow, suppressing healthy stem cells. The clonal mutation may result from genetic predisposition or from hematopoietic stem cell injury caused by exposure to any of the following:

Cytotoxic chemotherapy

Radiation

Viral infection

Genotoxic chemicals (eg, benzene)

MDS can be classified as primary (de novo) or secondary to aggressive treatment of other cancers, with exposure to radiation, alkylating agents, or topoisomerase II inhibitors; it also occurs in heavily pretreated patients with autologous bone marrow transplants.

In the early stages of MDS, the main cause of cytopenias is increased apoptosis (programmed cell death). As the disease progresses and converts into leukemia, further gene mutation occurs, and a proliferation of leukemic cells overwhelms the healthy marrow.

Etiology

Cytogenetically, patients with MDS or AML fall into three groups:

Normal karyotype

Balanced chromosomal abnormality causing the generation of fusion oncogenes

Complex karyotypes (usually >3 abnormalities)

Patients with complex karyotypes constitute 30% of primary MDS cases (only 20% of de novo AML) and up to 50% of therapy-related MDS and AML cases. These patients have a worse prognosis and response to treatment.

Balanced translocation abnormalities lead to the generation of fusion oncogenes such as Bcr-Abl in chronic myelogenous leukemia (CML) and PML-Rar alpha in acute promyelocytic leukemia (APL). Unbalanced recurrent aberrations, most commonly -5, 5q-,-7, 7q-, +8, 11q-, 13q-, and 20q-, suggest that genes within these regions have a role in the pathogenesis of MDS or myeloproliferative disorder (MPD), which is based on loss of tumor suppressor genes or haploinsufficiency of genes necessary for normal myelopoiesis.

Approximately 80% of patients with MDS do not have an obvious exposure or cause for MDS. In these cases, the disorder is classified as primary or idiopathic MDS.

The World Health Organiztion (WHO) classifies secondary MDS as MDS or acute leukemia that develops years after known exposure to sources of chromosomal damage. Patients who survive cancer treatment with alkylating agents, with or without radiotherapy, have a high risk of developing MDS or secondary acute leukemia 5-7 years after the exposure. These drugs are associated with a high prevalence of chromosomal abnormalities in bone marrow—in particular, the -5, del(5q), -7, del(q) and complex karyotype.

Secondary MDS after treatment with a topoisomerase II inhibitors such as an anthracycline or etoposide occurs 1-3 years after exposure to these agents. The chromosomal abnormalities commonly involve the MLL gene (11q23).

MDS may also develop after exposure to certain chemicals (eg, benzene). Insecticides, weed killers, and fungicides are also possible causes of MDS and secondary leukemia. [4] Viral infections have also been implicated. Less evidence supports genetic predisposition, but familial incidences have been described. Some of the congenital platelet disorders with RUNX1 and GATA2 mutations can predispose to MDS.

Although familial cases of myelodysplastic syndromes are rare, they are immensely valuable for the investigation of the molecular pathogenesis of myelodysplasia in general. [5] The best-characterized familial MDS is familial platelet disorder with propensity to myeloid malignancy, which is caused by heterozygous germline RUNX1 mutations. The incidence of MDS/AML in affected pedigrees is over 40%, with a median age of onset of 33 years. Familial monosomy 7; unusually short telomeres in dyskeratosis congenita; and four pedigrees with inherited MDS caused by heterozygous mutations in GATA2 have been reported. [6] These familial forms may occasionally be found in the course of screening family members of a patient with MDS as bone marrow transplant donors.

A study by Kristinsson et al found that chronic immune stimulation is a trigger for acute leukemia and MDS development. The underlying mechanisms may also be caused by a genetic predisposition or treatment for infections or autoimmune conditions. [7]

Epidemiology

The actual incidence of MDS in the United States is unknown. MDS was first considered a separate disease in 1976, and its occurrence was estimated at 1500 new cases every year. At that time, only patients with less than 5% blasts were considered to have this disorder. MDS was not classified as neoplastic and included in cancer registries until 2001. [8] Current estimates of the incidence of MDS in the United States vary widely, from 10,000 to 30,000-55,000 new cases each year. [8, 9, 10, 11] The higher figures have been questioned as possible overestimates resulting from inclusion of other hematopoietic conditions. [12]

The incidence of MDS has appeared to be increasing. The apparent rise is believed to reflect the increase in the elderly population, but may also reflect improvements in recognition and criteria for the diagnosis. [9]

Although MDS may occur in persons of any age, including children, MDS primarily affects elderly people, with the median onset in the seventh decade of life. Data from 2001 through 2003 of the first National Cancer Institute's Surveillance, Epidemiology & End Reports (SEER) indicate 86% of MDS cases were diagnosed in individuals who were 60 years of age or older (median age: 76y).

Other data from SEER also show that the estimated incidence of MDS increases significantly with age, ranging from 0.7 per 100,000 population during the fourth decade of life to 20.8-36.3/100,000 after age 70 years. There is a fivefold difference in risk between age 60 and ≥80 years.

At all ages, MDS is more common in males than in females. In SEER data from 2001-2003, the incidence rate was significantly higher in men than in women (4.5 vs 2.7 per 100,000 population). [13]

MDS is found worldwide and is similar in characteristics throughout the world. Data based mainly on European numbers from Germany and Sweden were very similar to the US numbers. [11]

A review of United Kingdom population-based data from September 2004 to August 2013 found marked variations in MDS incidence, depending on the standard population used to calculate rates. For example, using the 1996 world standard, the population with the greatest weighting towards younger groups, the incidence rate was 1.67 per 100,000 population; using the 2013 European Standard Population, which has the greatest weighting towards older ages, the rate was 4.4 per 100,000 population. [14]

Prognosis

In some patients, MDS is an indolent disease. Other patients develop significant cytopenias; the resulting complications (eg, bleeding and infections) account for almost all the mortality related to MDS. In the remainder of cases the disease follows an aggressive course and converts into an acute form of leukemia.

Risk classification systems to estimate prognosis in patients with MDS have been developed by the French-American-British (FAB) Cooperative Group, the World Health Organization (WHO), and the MDS Risk Analysis Workshop.

The FAB system classifies MDS into the following five subgroups, differentiating them from acute myeloid leukemia [15] :

Refractory anemia (RA)

RA with ringed sideroblasts (RARS)

RA with excess blasts (RAEB; 6-20% myeloblasts)

RAEB in transition to AML (RAEB-T; 21-30% myeloblasts)

Chronic myelomonocytic leukemia (CMML)

An underlying trilineage dysplastic change in the bone marrow cells is found in all subtypes.

RA and RARS are characterized by 5% or less myeloblasts in bone marrow. RARS is defined morphologically as having 15% erythroid cells with abnormal ringed sideroblasts (see the image below), reflecting an abnormal accumulation of iron in the mitochondria. Both RA and RARS have a prolonged clinical course and a low prevalence of progression to acute leukemia. In a review of United Kingdom population-based data, with followup of 2 to 11 years, progression to acute leukemia occurred in 5% of RARS cases, compared with 25% of RAEB cases. [14]

Bone marrow film (1000× magnification) demonstrati

Bone marrow film (1000× magnification) demonstrating ring sideroblasts in Prussian blue staining in a refractory anemia with excess of blasts in transformation. Courtesy of U. Woermann, MD, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland.

Myelodysplastic Syndrome (MDS) Clinical Presentation: History, Physical Examination

Updated: Apr 10, 2020

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History

The development of myelodysplastic syndrome (MDS) may be preceded by a few years by an unexplained macrocytic anemia with no evidence of megaloblastic anemia and a mild thrombocytopenia or neutropenia. Clinical symptoms that should prompt a workup for MDS are due to low peripheral blood counts, usually from the anemia but also from the thrombocytopenia or neutropenia.

Symptoms such as fatigue and malaise result from anemia. Signs and symptoms of chronic heart failure may develop in patients with underlying cardiac problems, depending on the degree of anemia.

Petechiae, ecchymoses, and nose and gum bleeding are common manifestations of a low platelet count. If underlying dysplastic changes were missed initially, thrombocytopenia as the presenting symptom may be mistaken for immune thrombocytopenia.

Fever, cough, dysuria, or shock may be manifestations of serious bacterial or fungal infections in patients with neutropenia.

Physical Examination

On physical examination, patients with myelodysplastic syndrome (MDS) may have evidence of thrombocytopenia, anemia, and/or neutropenia. Thrombocytopenia typically manifests as petechiae or ecchymoses; epistaxis and gum bleeding suggest severe thrombocytopenia. Hemoptysis, hematuria, and blood in stools may occur.

Pallor of the skin and mucosal membranes or evidence of fatigue, tachycardia, or congestive heart failure may be manifestations of severe anemia.

An enlarged spleen may be found in persons with chronic myelomonocytic leukemia (CMML), often indicating an overlap syndrome with MDS. CMML must be differentiated from chronic myelogenous leukemia (CML). Patients with an enlarged spleen may have complications related to spontaneous rupture and intra-abdominal exsanguination.

The presence of fever and infections, such as pneumonias and urinary tract infections, may be due to the neutropenia associated with MDS.

Myelodysplastic Syndrome (MDS) Differential Diagnoses

Updated: Apr 10, 2020

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Diagnostic Considerations

Myelodysplastic syndrome (MDS) is typically diagnosed by finding some combination of dysplastic cell morphology, increased marrow blasts, and a karyotypic abnormality. Other causes of cytopenias must be excluded. Common etiologies of cytopenias or morphologic abnormalities that may mimic MDS include the following [8] :

Medication (eg, methotrexate)

Deficiencies of cobalamin, folate, or copper

Alcohol abuse

HIV infection

Immune-mediated cytopenias (eg, aplastic anemia, large granular lymphocyte leukemia)

Congenital syndromes (eg, Fanconi anemia, X-linked sideroblastic anemia)

Idiopathic cytopenia of undetermined significance (ICUS)

Idiopathic dysplasia of undetermined significance (IDUS)

Idiopathic Cytopenia of Undetermined Significance (ICUS)

Idiopathic Dysplasia of Undetermined Significance (IDUS)

Myelodysplastic Syndrome (MDS) Workup: Approach Considerations, Complete Blood Count and Peripheral Blood Smear, Bone Marrow Studies

Significant changes are found in the blood counts and morphology of patients with MDS. The peripheral blood count may show a single cytopenia (anemia, thrombocytopenia, or neutropenia) in the early phase or bicytopenia (2 deficient cell lines) or pancytopenia (3 deficient cell lines) in later stages.

Anemia varies in degree from mild to severe. It is usually macrocytic (mean cell volume of >100 fL) with red blood cells (RBCs) that are oval-shaped (macro-ovalocytes). It is usually dimorphic (2 or more populations), with a normal or a hypochromic microcytic population (RARS) coexisting with the macrocytes. Punctate basophilia is observed in RBCs.

Neutropenia may vary from mild to severe. Morphologic abnormalities are often observed in the granulocytes. These can include bilobed or unsegmented nuclei (pseudo–Pelger-Huet abnormality) or hypersegmentation on the nuclei (6-7 lobes) similar to megaloblastic diseases.

Granulation abnormalities vary from an absence of granules to abnormal distribution inside the cytoplasm (Dohle bodies).

Platelet counts are decreased (rarely increased). Abnormalities such as giant hypogranular platelets and megakaryocyte fragments are present.

Bone Marrow Studies

In most cases, bone marrow changes include hypercellularity with trilineage dysplastic changes. A small number of patients may have a hypocellular marrow. This often overlaps with aplastic anemia. Increased marrow fibrosis may be confused with other myeloproliferative disorders. Dysplastic changes in RBC lineage (dyserythropoiesis) are characteristic. In the absence of vitamin B-12 or folate deficiencies, the bone marrow usually exhibits asynchronous maturation of nuclei and cytoplasm similar to that described in megaloblastic anemias.

Other changes include binuclearity or multinuclearity in the erythroid cell precursor cells and the presence of ringed sideroblasts (iron accumulation in the mitochondria). Refractory anemia with ringed sideroblasts (RARS) is one of the MDS types in the French-American-British (FAB) Cooperative Group classification system. (See the image below.)

Bone marrow film (1000× magnification) demonstrati

Dysplastic changes in white blood cell (WBC) lineage (dysmyelopoiesis) involve myeloid hyperplasia with an increased number of myeloblasts and an expanded myelocyte and metamyelocyte population (midstage bulge). This separates it from acute leukemia (leukemic hiatus or absence of mid stage). In the FAB classification, the percentage of myeloblasts separates RA (< 5%), RAEB (5-20%), RAEB in transformation (>20, < 30%), and acute myeloid leukemia (AML; >30%).

The 2008 update of the WHO classification considers single-lineage dysplasia as a valid criterion for diagnosis of MDS, and refractory cytopenia with unilineage dysplasia (RCUD) became an official entity in that classification. In 2004, WHO revised the percentage of blasts that defines AML from 30% to 20%; thus, the RAEB in transformation entity has become officially AML.

Morphologic abnormalities are evident in nuclear-cytoplasm dissociation in maturation and when the pseudo–Pelger forms are also present in bone marrow.

Dysthrombopoiesis in the platelet production cell lineage consists of micromegakaryocytes (dwarf forms) with poor nuclei lobulation and giant platelets budding off from their cytoplasm.

Cytogenetic Studies

Cytogenetic techniques have evolved from individual chromosome identification by banding techniques to the new, more sensitive color-coded methods. Separating individual chromosomes is dependent on the ability to induce the cell into mitosis to identify abnormalities. The new technique uses fluorescent in situ hybridization (FISH) and color-coded chromosomes to enable observation of the intact cell without requiring mitosis.

Cytogenetic studies of the bone marrow cells indicate mutations into clonal cell lines, with abnormal chromosomes in 48-64% in different series. With higher-resolution techniques (eg, FISH), some practitioners claim a 79% rate of chromosomal abnormalities in patients with primary MDS.

Chromosomal abnormalities are clonal and include 5q-, monosomy 7 (-7) or 7q-, trisomy 8 (+8), and numerous other less frequent abnormalities. Multiple combinations may be present; this indicates a very poor prognosis. A single abnormality, except those involving chromosome 7, usually indicates good prognosis and survival.

The WHO classification is helpful in predicting subgroup differences in prognosis and response to treatment in patients with MDS. Refractory cytopenias are divided into those in which multi-lineage dysplasia is absent (RCMD-) or present (RCMD+) and those with ringed sideroblasts (RCMD+/+RS) or without ringed sideroblasts (RCMD/-RS).

A new subcategory includes patients with isolated deletion of chromosome 5q (5q-) and less than 5% blasts, called the 5q- syndrome. [22] Identification of the syndrome or presence of this particular cytogenetic abnormality is useful because the majority of these patients will respond to treatment with lenalidomide (Revlimid).

Unclassified by the WHO are the group of patients with MDS whose conditions overlap with severe aplastic anemia and paroxysmal nocturnal hemoglobinuria. This group includes MDS patients with the FAB-RA subtype who may have a hypoplastic marrow, usually have a human leukocyte antigen (HLA)-DR15 phenotype, are young (< 60 years), may have cells deficient in CD55 and CD59, and respond to immunosuppressive treatment with anti-thymocyte globulin (ATG) or cyclosporin. [23]

Histologic Findings

The presence of dysplastic changes in the peripheral blood smear and trilineage dysplasia and hypercellular marrow in the absence of vitamin deficiency is diagnostic of MDS. The presence of typical chromosomal abnormalities supports the diagnosis and contributes to determining the prognosis of MDS. (See the following images.)

Blood film (1000× magnification) demonstrating a v

Staging

In 1997, an international group of experts, the MDS Risk Analysis Workshop, developed the International Prognostic Scoring System (IPSS) for staging MDS. [18] The IPSS was revised in 2012 to accommodate advances in defining cytogenetic abnormalities. [19] The revised IPSS (IPSS-R) also includes a more detailed consideration of cytopenias. (See Tables 2-4, below.) An online calculator for determining an individual patient's R-IPSS score is available on the MDS Foundation Web site.

Table 2 Cytogenetic abnormalities assigned an IPSS-R value for scoring (Open Table in a new window)

Cytogenetic prognostic subgroups

Cytogenetic abnormalities

Very good

-Y, del(11q)

Good

Normal, del(5q), del(12p), del(20q), double

including del(5q)

Intermediate

Del(7q), +8, +19, t(17q), any other single or

double independent clones

Poor

-7, inv(3)/t(3q)/del(3q), double including

-7,/del(7q), complex: 3 abnormalities

Very poor

Complex: >3 abnormalities

Table 4. IPSS-R prognostic risk scores and categories (Open Table in a new window)

Risk Score

Risk Category

≤1.5

Very Low

>1.5-3

Low

>3-4.5

Intermediate

>4.5-6

High

Very High

Calculation of the IPSS-R score in 7012 patients with MDS resulted in the following risk categorizations [19] :

Very low: 19%

Low: 38%

Intermediate: 20%

High: 13%

Very high: 10%

Clinical outcome according to IPSS-R risk category in those patients is outlined in Table 5, below.

Table 5. Clinical outcome by IPSS-R risk category (Open Table in a new window)

IPSS-R Risk Category

Very Low

Low

Intermediate

High

Very High

Clinical Outcome

Median survival (years)

8.8

5.3

3.0

1.6

0.8

Median time to 25% acute myelogenous leukemia evolution (years)

10.8

3.2

1.4

0.7

Classification of the subtypes or categories of MDS has changed from the FAB classification to the WHO classification. (See Table 6, below.)

Table 6. Categories of FAB classification versus WHO classification for myelodysplastic syndrome (MDS) (Open Table in a new window)

FAB

Classification

WHO–2004

Classification

WHO–2008

Classification

RA RCMD 5q-

RCUD RCMD 5q-

RARS

RARS RCMD-RS

RARS RCMD-RS RARS-T

RAEB

RAEB-1 RAEB-2

CMML

CMML-1 CMML-2

RAEB-T

AML

FAB – French-American-British Cooperative Group; WHO – World Health Organization; RA – Refractory anemia; RARS – RA with ringed sideroblasts; RAEB – RA with excess blasts; RAEB-T – RAEB in transition to AML; AML – Acute myelogenous leukemia; CMML – Chronic myelomonocytic leukemia; RCMD – Refractory cytopenia with multilineage dysplasia; RCUD – Refractory cytopenia with unilineage dysplasia

CMML in the FAB classification requires an actual monocyte count of more than 1000/μL with trilineage dysplasia.

WHO classifies CMML into the following:

Juvenile and proliferative CMML under MDS/myeloproliferative neoplasma (MPN have more than 13,000/μL monocytes plus splenomegaly.

CMML under MDS is limited to monocytosis of less than 13,000/μL with trilineage dysplasia.

Laboratory Studies

In addition to blood counts, peripheral blood smears, and bone marrow studies, the National Comprehensive Cancer Network (NCCN) recommends the following studies in patients with suspected MDS [21] :

Serum erythropoietin (prior to red blood cell [RBC] transfusion)

RBC folate and serum vitamin B-12

Serum ferritin, iron, and total iron-binding capacity (TIBC)

Thyroid-stimulating hormone (TSH)

Lactate dehydrogenase (LDH)

HIV testing if clinically indicated

NCCN guidelines also recommend considering evaluation of copper deficiency in patients with GI malabsorption, severe malnutrition, gastric bypass surgery, or patients on zinc supplementation.

Myelodysplastic Syndrome (MDS) Treatment & Management: Approach Considerations, Supportive Care, Pharmacologic Therapy

Approach Considerations

The standard care for patients with myelodysplastic syndrome (MDS) and decreased blood counts is constantly changing. Supportive therapy, including transfusions of the cells that are deficient (ie, red blood cells [RBCs], platelets), and treatment of infections are the main components of care. [24]

The approach to therapy is based on the revised International Prognostic Scoring System (IPSS-R) score, the patient's age and co-morbidities, and the patient's expectations and personal goals. The more toxic and aggressive forms of therapy, such as stem cell transplantation and aggressive chemotherapy, are reserved for younger and fit patients with high-risk disease.

Cytotoxic chemotherapy is used in patients with MDS who have increasing myeloblasts and those who have progressed to acute leukemia. The usual combination treatment is cytarabine plus an anthracycline, which yields a limited response rate of 30-40%. Elderly patients experience high rates of morbidity and mortality with this approach and should consider treatment with the hypomethylating agent azacytidine, which has been shown to improve survival compared with either supportive or aggressive therapy and is approved for use in MDS by the US Food and Drug Administration (FDA).

Patients with MDS should be under the care of a hematologist. Because most treatments for MDS are not standard and are considered experimental, referral to a tertiary care center with bone marrow transplantation capabilities is often necessary.

Although treatment of symptoms improves quality of life in MDS, these measures are temporary. More long-term measures are necessary to stimulate the patient's bone marrow production of mature blood cells. Practitioners are encouraged to refer patients for participation in clinical trials at academic centers and the MDS Centers of Excellence.

Supportive Care

Supportive care includes transfusion of red blood cells (RBCs) or platelets. The goal is to replace cells that are prematurely undergoing apoptosis in the patient's bone marrow.

Decrease transfusion-related complications by using leukocyte-depleted blood products, which have been shown to decrease nonhemolytic febrile reactions, prevent alloimmunization and platelet refractoriness, and prevent cytomegalovirus transmission. Additionally, this practice has been shown to achieve better quality control of blood products compared with bedside filtering and to be cost effective.

Red blood cell transfusion

Patients with moderate-to-severe anemia require RBC replacement (see the image below). Transfusing packed RBCs for severe or symptomatic anemia benefits the patient temporarily, only for the life span of the transfused RBCs (2-4 wk). Patients with congestive heart failure may not tolerate the same degree of anemia as young patients with normal cardiac function, and slow or small-volume (eg, packed RBCs) transfusions with judicious use of diuretics should be considered. For bone marrow transplantation candidates who are cytomegalovirus (CMV) negative, CMV-negative or leukopheresed) blood products are recommended whenever possible. [21]

This bone marrow film (400× magnification) demonst

This bone marrow film (400× magnification) demonstrates an almost complete replacement of normal hematopoiesis by blasts in a refractory anemia with an excess of blasts in transformation. Note the signs of abnormal maturation such as vacuolation, double nucleus, and macrocytosis. Courtesy of U. Woermann, MD, Division of Instructional Media, Institute for Medical Education, University of Bern, Switzerland.

Iron chelation

Patients with low-risk or intermediate-1–risk MDS typically have long-term survival and may receive multiple RBC transfusions. These patients may develop transfusion-induced iron overload and can incur significant damage of the liver, heart, pancreas, and other tissues. In addition, some evidence suggests that iron overload in the bone marrow adds to the cellular early apoptosis contributed by the microenvironment. [25]

Current guidelines recommend starting iron chelation therapy in those patients who have received 20-25 units of packed RBCs or who have a serum ferritin level of > 1000 μg/L. [26]

Deferoxamine (Desferal) is difficult to administer in elderly patients because it has to be given subcutaneously by pump over 12 hours daily to be effective. It is often given at the same time as the RBC transfusion, although in fact that is ineffective.

Deferasirox (Exjade) is an FDA-approved dispersible tablet that is dissolved in 7 oz of water and taken by mouth once daily. It is excreted in stools rather than urine, and it is 100-fold more active as a chelator of iron. Patients who cannot tolerate side effects such as diarrhea may require dose modification.

Platelet transfusion

Platelet transfusion is beneficial to stop active bleeding in thrombocytopenic patients, but the life span of transfused platelets is only 3-7 days. Avoid repeated and frequent platelet transfusions on the basis of low platelet counts (< 20,000/µL) in patients who are not experiencing clinical bleeding.

Long-term measures to prevent skin and mucosal bleeding may be achieved by administering oral antithrombolytic agents such as prophylactic oral epsilon-aminocaproic acid (Amicar) to avoid alloimmunization.

Treatment of neutropenia

Treat infections and neutropenia. Some patients may require granulocyte transfusions, but the risk of alloimmunization is high, as is the risk of developing refractoriness to future transfusion therapy. Life-threatening infections, especially of fungal etiologies, require administration of granulocytes and antifungal agents. Prophylactic antibiotics and antifungal agents may be considered in extrememly high risk patients with severe neutropenia. [27]

Bone marrow stimulation

Hematopoietic growth factors can stimulate bone marrow cell production and decrease excess bone marrow cell apoptosis. These erythropoiesis-stimulating agents (ESAs) include the recombinant human erythropoietin (EPO) agents epoetin alfa and darbepoetin alfa. [28]

National Comprehensive Cancer Network (NCCN) guidelines recommend the use of ESAs for treatment of symptomatic anemia in patients in the R-IPSS very low risk, low risk, or intermediate risk category whose tumor lacks the 5q31 deletion and whose level of endogenous EPO is ≤500 mU/mL. [21] These patients should receive epoetin alfa, 40,000–60,000 U subcutaneously (SC), 1–3 times weekly; or darbepoetin alfa, 150–300 μg SC weekly.

During ESA treatment, iron supplementation should be considered for patients with a transferrin saturation < 20%. If the patient responds to ESA treatment, an attempt should be made to reduce the ESA dose (or the frequency of administration) to the lowest able to maintain the hemoglobin level between 10 and 12 g/dL.

In cases of the presence of ringed sideroblasts or an absence of response, the addition of granulocyte colony-stimulating factor (G-CSF; filgrastim, filgrastim-sndz, or tbo-filgrastim), 1–2 μg/kg 1–3 times per week should be considered. The combination of ESAs and G-CSF should be considered only for patients who are not heavily transfusion dependent (fewer than 2 RBC units per month), have serum erythropoietin levels < 500 mU/mL, and are not responding to ESAs alone. For patients with a serum EPO ≤500 mU/mL and ring sideroblasts < 15% who have no response to an ESA alone, the NCCN suggests. adding lenalidomide plus or minus G-CSF. [21]

Of MDS patients with neutropenia, 75% respond to G-CSF. [29] Of MDS patients with anemia and neutropenia, 75% respond to a combination of an ESA and G-CSF for their neutropenia, with a 50% increase in erythroid response. The addition of low doses of G-CSF synergistically enhances the erythroid response to ESAs—in particular, patients who have refractory anemia with ringed sideroblasts (RARS).

A re-analysis that used the World Health Organization classification demonstrated a significantly better response in RARS (75%) than in refractory cytopenia with multilineage dysplasia and ringed sideroblasts (RCMD-RS; 9%). This may reflect G-CSF's ability to strongly inhibit cytochrome c release and hence mitochondria-mediated apoptosis in RARS erythroblasts.

Thrombopoietin receptor agonists (TPO-RA) such as romiplostim and eltrombopag have been approved to treat immune thrombocytopenia. Their use in MDS is limited in current practice owing to the increase in the blast percentage seen with the use of eltrombopag in some studies.

Pharmacologic Therapy

Cytotoxic chemotherapy is used in patients with MDS with increasing myeloblasts and those who have progressed to acute leukemia. The usual combination treatment is a cytarabine-anthracycline combination, which yields a response rate of 30-40% (high complication rate and morbidity in elderly patients).

New drug combinations using hematopoietic growth factors and new drugs, such as topotecan (Hycamtin), are yielding better response rates with lower morbidity. Aggressive chemotherapy may be indicated in small populations of elderly patients with good performance status and no associated serious medical comorbidity.

Isotretinoin or 13 cis-retinoic acid (Accutane) is the most active retinoid. In a randomized placebo-controlled trial in 70 MDS patients treated with low-dose isotretinoin (20 mg/m2/d), 1-year survival among patients with refractory anemia was 77%, compared with 36% in the placebo group. [30] This is statistically significant, although this form of therapy is not generally accepted. The author limits this treatment to patients who are not transfusion dependent.

A more recent study found that elderly MDS patients (n=63) with unfavorable features for response to erythropoietin alone had a 60% erythroid response rate to combination treatment with erythropoietin, isotretinoin, and vitamin D. Long-term follow-up showed a median erythroid response duration of 17 months, with 20% of patients still in response after 6 years of therapy—a longer duration than has been documented in most studies of treatment with erythropoietin alone. [31]

Lenalidomide

Lenalidomide is a 4-amino-glutarimide thalidomide analogue that is more potent than thalidomide but lacks its neurotoxicity and teratogenic effects. It is active in patients with MDS categorized as low risk or intermediate risk–1 according to the International Prognostic Scoring System (IPSS).

Lenalidomide is the drug of choice in MDS with 5q deletion syndrome. In particular, patients with the karyotype characterized by deletion 5q31 show the best response. List et al reported an erythroid response in 76% of these patients, with 67% no longer requiring transfusions; 73% of their 148 patients had a cytogenetic response, 45% had a complete cytogenetic remission, and 36% achieving a normal bone marrow histologically. [32]

In an earlier study by List et al, erythroid responses occurred in 57% of MDS patients with a normal karyotype, in 68% of those in the IPSS low-risk category, and 50% of those in the intermediate–1 risk category. [33]

Although the best responses have been observed in MDS patients with isolated 5q deletion, responses may also be elicited in patients with 5q deletion and other chromosomal abnormalities. However, treatment should be limited to patients without the p53 mutation. Thus, assessment of an additional molecular marker may be necessary before committing to this treatment in those patients.

Hypomethylating agents

Epigenetic modulation of gene function is a very powerful cellular mechanism. DNA methylation leads to silencing of suppressor genes, increasing the risk for transformation to acute myelogenous leukemia (AML). Azacitidine and decitabine are the two hypomethylating agents currently used in the treatment of MDS. Azacitidine and decitabine may reduce hypermethylation and induce re-expression of key tumor suppressor genes in MDS. [34]

Azacitidine and decitabine are approved by the US Food and Drug Administration for treatment of all 5 MDS subtypes. They are considered standard therapy for both low-risk cases without 5q-, as well as intermediate and high-risk MDS. Although the two drugs were thought to be similar, only azacytidine has additional RNA and DNA activity compared with decitabine.

In a pivotal trial that included patients in all stages of MDS, patients treated with azacitidine showed a 37% response (7% complete response, 16% partial response) versus a 5% response in the control arm, with an improved median time to transformation or death (21 mo for azacitidine vs 13 mo for controls) and transformation to leukemia (15% for azacitidine vs 38% for controls). [35]

Compared with supportive care, both agents show an overall response (60% with azacytidine vs 5% with decitabine) and a longer time to progression to AML or death, and improvement of quality of life but no overall survival advantage. In a phase III trial involving 358 patients with an IPSS classification of intermediate-2 or high risk, treatment with azacytidine (75 mg/m2/d for 7 d q28d) significantly increased survival. At 2 years, 50.8% of patients in the azacitidine group were alive compared with 26.2% in the patients who received conventional care. [36]

After sequencing 40 recurrently mutated myeloid malignancy genes in tumor DNA from 213 MDS patients, Bejar et al reported that response to hypomethylating agents was most likely to occur in patients with TET2 mutations and wild-type ASXL1, a pattern found in 10% of the MDS cases in their study. However, these authors note that their study did not identify any mutations that reliably and strongly predicted primary resistance to treatment, and thus their findings provide no genetic rationale for denying treatment with hypomethylating agents to any patients with MDS. [37]

Immunosuppressive therapy

Some cases of MDS have an autoimmune process underlying the pancytopenia and respond to immunosuppressive therapy (IST). However, identifying these cases is problematic.

A portion of these cases represent an overlap between aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and MDS. These patients are usually younger and may have hypoplastic bone marrow with dysplasia and cytogenetic abnormalities (separate from AA). In addition, they may have a small clone of PNH cells, but these typically constitute less than 3% of cells and require a special sensitive flow cytometry to be detected. Indeed, as little as 0.126% of granulocytes and 0.001% of erythrocytes (PNH-type cells) are positive.

A feature of some of these cases is HLA-A allele–lacking leukocytes (HLA-LLs). These are derived from hematopoietic stem cells that develop copy number–neutral loss of heterozygosity of the HLA haplotype owing to uniparental disomy of the short arm of chromosome 6 (6pUPD).

Patients with MDS who have a thrombopoietin (TPO) level ≥320 pg/mL (TPO high patients) exhibit a high progression-free survival rate and good response to IST, similar to cases of AA. The small number of cases reported and the limited access to the special tests required make it difficult to place these into perspective for general clinical use.

Trials of IST in MDS have used cyclosporine (56%); rabbit (27%) or horse (35%) anti-thymocyte globulin (ATG); alemtuzumab; and recently, sirolimus. At the author's institution, a combination of ATG and cyclosporine is used in AA. Studies of this combination in MDS have reported response rates of only 16-30%, however, which is problematic, especially in view of the small number of patients studied. [38] Responses have mostly been observed in notably lower-risk MDS and patients with HLA-DR15 positivity. Consequently, this form of therapy is considered experimental and should be performed in the setting of clinical trials.

Luspatercept

Patients with lower-risk MDS and anemia in whom ESA therapy is not effective generally become dependent on RBC transfusions. Luspatercept-aamt is a recombinant fusion protein that promotes RBC maturation by binding several endogenous transforming growth factor (TGF)–β superfamily ligands, thereby diminishing Smad2/3 signaling.

In April 3, 2020, the FDA approved luspatercept-aamt (Reblozyl) for treatment of anemia in adult patients with very low– to intermediate-risk MDS with ring sideroblasts (MDS-RS) or with myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T). Patients must have experienced failure of ESA therapy and must be requiring transfusion of 2 or more RBC units over 8 weeks.

Approval was based on the MEDALIST trial, a randomized, multicenter, double-blind, placebo-controlled trial in 229 transfusion-dependent patients with very low– to intermediate-risk MDS-RS or MDS-RS-T. By 24 weeks, 38% of patients in the luspatercept-aamt arm had achieved the study's main endpoint of transfusion indepence for 8 weeks or longer, compared with 13.2% of those in the placebo group (P< 0.001). [39]

Experimental agents

New drugs for MDS are being generated at a brisk pace as new clinical trials continue to make inroads on improving outcomes in quality of life and, ultimately, in overall survival. Synergy is being sought with new combinations of the active drugs and the less active drugs. As more is being learned about the biology of MDS through the molecular mechanisms and the ability to modify these molecular targets, research has opened new doors for the treatment of this once obscure and poor-outcome disease. [40]

Bone Marrow Transplantation

Bone marrow transplantation with a matched allogeneic or syngeneic donor is used in patients with poor prognoses or late-stage MDS who are aged 55 years or younger and have an available donor. Among selected patients with less advanced/low-risk MDS (< 5% marrow myeloblasts), a 3-year survival of 65-75% is achievable with HLA-matched related and unrelated donors. Because hematopoietic stem cell transplantation (HSCT) offers the potential for cure, the timing of the procedure may be important in this subgroup of patients. [41, 42]

Compared with patients with de novo acute myeloid leukemia transplanted in first remission, patients with MDS experience higher mortality rates associated with the procedure (21-30% vs 10%), lower disease-free survival rates, and higher relapse rates (70% vs 40%). Among patients with more advanced/high-risk disease (≥5% marrow myeloblasts and high IPSS scores), the probability of posttransplant relapse ranges from 10-40%; as a result, relapse-free survival is inferior in this group.

Because most patients with MDS are elderly and only a few young patients will have a matched donor, the use of bone marrow transplantation is limited. However, in our institution, with a haploidentical (half-match) donor, 2-step protocol, we have shown that expanding the donor pool to include patients' children as well as siblings increases the availability of donors for elderly patients and produces the same result as transplantation from full-match donors. Sandhu et al reported that umbilical cord blood transplantation after reduced-intensity conditioning regimens in patients aged ≥70 years with MDS and AML produced results comparable to those of HLA full-matched sibling donor transplantation in this age group. [43]

The use of nonmyeloablative (mini) bone marrow transplantation and reduced-intensity conditioning regimens has been used in elderly patients as old as 75 years with some success. This approach is still considered experimental and should be performed only in a clinical trial setting.

Shaffer and colleagues developed a system that can be used to determine prognosis in patients undergoing HLA-matched and -mismatched allogeneic HSCT for MDS. [44] In the system, the following risk factors are assigned 1 point:

Blood blasts >3%

Platelet count ≤50 × 10 9/L at transplantation

Karnofsky performance status < 90%

Comprehensive cytogenetic risk score of poor or very poor

Age 30 to 49 years

Risk factors assigned 2 points are as follows:

Monosomal karyotype

Age 50 years or older

Increasing score proved predictive of increased relapse (P < 0.001) and treatment-related mortality (P < 0.001) in HLA-matched patients and predictive of relapse (P < 0.001) in the HLA-mismatched cohort. The 3-year overall survival rates after transplantation, by point score, were as follows:

Low (0-1 point): 71% (95% confidence index [CI], 58-85%)

Intermediate (2-3 points): 49% (95% CI, 42-56%)

High (4-5 points): 41% (95% CI, 31-51%)

Very high (≥6 points): 25% (95% CI, 4-46%)

Lindsley et al reported that the presence of specific genetic mutations may predict clinical outcomes in patients who undergo allogeneic HSCT for MDS. [45] Their findings included the following:

TP53 mutations were associated with shorter survival and a shorter time to relapse.

RAS pathway mutations (in patients 40 years of age or older who did not have TP53 mutations) were associated with shorter survival, due to a high risk of relapse; however, the increased risk of relapse was evident only in patients who received reduced-intensity conditioning.

JAK2 mutations were associated with shorter survival due to a high risk of death without relapse.

Young adults with compound heterozygous mutations in the Shwachman-Diamond syndrome–associated SBDS gene with concurrent TP53 mutations had a poor prognosis.

Surgical Care

In the past, splenectomy was performed in patients with an enlarged spleen to treat the cytopenias or transfusion refractoriness. With current therapy, splenectomy is not indicated ; indeed, it could be disastrous in this condition.

Myelodysplastic Syndrome (MDS) Guidelines: Guidelines Summary, Diagnosis, Prognostic Scoring Systems

Guidelines Summary

Myelodysplastic Syndrome (MDS) Classification

In 2016, the World Health Organization (WHO) released a revision to its 2008 classification scheme for myelodysplastic syndrome (MDS). [46, 17] The National Comprehensive Cancer Network (NCCN) has included the revised WHO classificaton system in its 2017 updated guidelines. [21]

The two systems are compared in the table below..

Table. 2008 and 2016 World Health Organization (WHO) classifications of myelodysplastic syndromes (Open Table in a new window)

2008 WHO Classification [17] 2016 WHO Classification [46]

Refractory cytopenia with unilineage dysplasia (RCUD) encompassing refractory anemia (RA), refractory neutropenia (RN), and refractory thrombocytopenia (RT) MDS with single lineage dysplasia (MDS-SLD)

Refractory cytopenia with multilineage dysplasia (RCMD) MDS with multilineage dysplasia (MDS-MLD)

Refractory anemia with ringed sideroblasts (RARS)

MDS with ring sideroblasts (MDS-RS)

MDS-RS with single lineage dysplasia (MDS-RS-SLD)

MDS-RS with multilineage dysplasia (MDS-RS-MLD)

Myelodysplastic syndrome associated with isolated del(5q) MDS with isolated del(5q)

MDS with excess blasts (MDS-EB)

Refractory anemia with excess blasts–1 (RAEB-1) MDS-EB-1

Refractory anemia with excess blasts–2 (RAEB-2) MDS-EB-2

Myelodysplastic syndrome, unclassified (MDS-U) MDS, unclassifiable (MDS-U)

with 1% blood blasts

with single lineage dysplasia and pancytopenia

based on defining cytogenetic abnormality

Refractory cytopenia of childhood Refractory cytopenia of childhood

Diagnosis

The NCCN utilizes the WHO classification system for diagnosis and distinguishes subtypes on the basis of blood and bone marrow findings. [21, 46]

MDS with single-lineage dysplasia (MDS-SLD) criteria are as follows:

Blood: single cytopenia or bicytopenia

Bone marrow: dysplasia in ≥ 10% of one cell line, < 5% blasts

MDS with ring sideroblasts (MDS-RS) criteria are as follows:

Blood: anemia, no blasts

Bone marrow: ≥ 15% of erythroid precursors with ring sideroblasts, or ≥ 5% blasts ring sideroblasts if SF3B1 mutation is present

MDS with multilineage dysplasia (MDS-MLD) criteria are as follows:

Blood: cytopenia(s), < 1 × 109/L monocytes

Bone marrow: dysplasia in ≥ 10% of cells in ≥ 2 hematopoietic lineages; < 15% ring sideroblasts (or < 5% ring sideroblasts if SF3B1 mutation present), < 5% blasts

MDS with excess blasts-1 (MDS-EB-1) criteria are as follows:

Blood: cytopenia(s) ≤2-4% blasts, < 1 × 109/L monocytes

Bone marrow: unilineage or multilineage dysplasia, no Auer rods, 5-9% blasts

MDS with excess blasts-2 (MDS-EB-2) criteria are as follows:

Blood: cytopenia(s), 5-19% blasts, < 1 × 109/L monocytes

Bone marrow: unilineage or multilineage dysplasia, ±Auer rods, 10-19% blasts

Myelodysplastic syndrome–unclassified (MDS-U) criteria are as follows:

Blood: cytopenias, ±1% blasts on at least 2 occasions

Bone marrow: unilineage dysplasia or no dysplasia but characteristic MDS cytogenetics, < 5% blasts

Myelodysplastic syndrome associated with isolated del(5q) criteria are as follows:

Blood: anemia, platelet levels normal or increased

Bone marrow: unilineage erythroid dysplasia, isolated del(5q), < 5% blasts ± one other abnormality except -7/del(7q)

The following prognostic scoring systems are most commonly used:

International Prognostic Scoring System (IPSS and IPSS-R)

WHO Prognostic Scoring System (WPSS)

Lower-Risk Prognostic Scoring System (LR-PSS)

NCCN guidelines prefer the IPSS-R over the IPSS or WPSS, and find its predictive power to be comparable to LR-PSS. [21] The 2014 European Society of Medical Oncology (ESMO) guidelines also recommend IPSS-R while noting that gene mutation profiling (ie, TP53, EZH2, ETV6, RUNX1, ASXL1) may also improve risk stratification but data are still lacking to recommend its use in routine practice. [47] In contrast, the 2013 European LeukemiaNet (ELN) guidelines recommends that all patients be risk stratified using IPSS. [48]

International Prognostic Scoring System

The IPSS has been the most widely used prognostic scoring system for MDS. First published in 1997, it was intended for use with the French-American-British (FAB) classification system which has since been largely supplanted by the World Health Organization (WHO) classification system. The following three factors are rated [18] :

The percentage of blasts in the bone marrow (scored on a scale from zero to 2)

Karyotype (scored from zero to 1)

Cytopenias (scored as zero or 0.5)

Each factor is given a score and totaled and the patient’s risk is classified according to the following:

0 = Low risk

0.5-1 = Intermediate risk - 1

1.5-2 = Intermediate risk - 2

≥2 = High risk

In 2012, a revised IPSS (IPSS-R) was released with five risk groups (very low, low, intermediate, high and very high). It refined the original model by incorporating more detailed cytogenetic prognostic categorization and cut-offs for hemoglobin levels, platelet counts and neutrophil count. The prognostic score is now weighted according to the severity of cytopenias in addition to the bone marrow blast percentage. [19]

WHO Prognostic Scoring System (WPSS)

The WHO Prognostic Scoring System (WPSS) was developed in 2005 based on the 2001 WHO classifications and refined most recently in 2011. [49, 50] In contrast to the IPSS and IPSS-R, which are applied only at the time of diagnosis, the WPSS is dynamic, and patients can be reassigned categories as their disease progresses. The WHO score is calculated on the basis of the following three factors [50] :

WHO disorder classification (0-3)

Karyotype (0-2)

Presence or absence of severe anemia (0-1)

Based on the total score, risk classification is as follows:

0 = Very Low

1 = Low

2 = Intermediate

3-4 = High

≥5 = Very High

Lower-Risk Prognostic Scoring System (LR-PSS)

In 2008, researchers at MD Anderson Cancer Center developed the Lower-Risk Prognostic Scoring System (LR-PSS) to identify patients with very low or low risk with a poorer prognosis. The model is a refinement of IPSS and included the following factors that were independent predictors of survival outcomes [51] :

Unfavorable cytogenetics

≥60 years old

Decreased hemoglobin level

Decreased platelet count

Higher percentage of bone marrow blasts

Each factor was given a weighted score and based on the total, patients were assigned to one of the following risk categories:

Treatment

Guidelines for the management of MDS have been issued by the following organizations:

National Comprehensive Cancer Network (NCCN) [21]

European LeukemiaNet (ELN) [48]

European Society of Medical Oncology (ESMO) [47]

Supportive Care

The NCCN guidelines recommend supportive care as the standard of care for patients with lower-risk MDS. Supportive care includes the following [21] :

Clinical monitoring, psychosocial support and quality of life assessment

Red blood cell (RBC) transfusions for symptomatic anemia

Platelet transfusions for thrombocytopenic bleeding; aminocaprioic acid may be considered for profound thrombocytopenia

Cytomegalovirus (CMV)-negative or leuko-reduced blood products for CMV-negative transplant candidates

No routine antibiotic prophylaxis except in patients with recurrent infections

Management of iron overload in patients who have received >20 to 30 RBC transfusions with deferoxamine subcutaneously or deferasirox orally, except in patients with low creatinine clearance (< 40 mL/min)

Low-risk MDS

In lower-risk MDS patients, all three guidelines recommend the following for treatment of symptomatic anemia [21, 48, 47]

Patients without del(5q): Erythropoiesis-stimulating agents (ESAs); recombinant erythropoietin (EPO) or darbepoetin (DAR); granulocyte colony-stimulating factor (G-CSF) may be added

Patients with del(5q): Lenalidomide

For patients with neutropenia and thrombocytopenia, NCCN guidelines recommend azacitidine/decitabine or immunosuppressive therapy in selected cases. [21]

High-risk MDS

NCCN guidelines recommendations for treatment of higher-risk MDS include the following [21] :

Allogeneic hematopoietic stem cell transplant (HSCT)

For non-transplant candidates or for candidates with no response or relapse after transplantation, azacitidine (preferred; category 1) or decitabine

The ESMO and ELN guidelines offer similar recommendations. [48, 47]

Medication Summary

Treatment of myelodysplastic syndrome (MDS) is based on the stage and mechanism of the disease that predominates the particular phase of the disease process. In the early phases, when increased bone marrow apoptosis results in ineffective hematopoiesis, retinoids and hematopoietic growth factors are indicated.

In late stages, with inevitable leukemic transformation, cytotoxic chemotherapy and bone marrow transplantation may be necessary. All of these modes of therapy are undergoing clinical trials to determine the overall benefit to quality of life and survival.

Patients with associated serious medical comorbidities should be treated with less aggressive agents such as azacitidine or arsenic trioxide (Trisenox), or they should be entered into a clinical trial. However, these are currently in the early experimental stages.

Retinoid-lilke Agents

Class Summary

Retinoids are the most active agents in MDS. Vitamin D-3 also has activity but is not of clinically significant value.

Isotretinoin or 13 cis-retinoic acid (Claravis, Amnesteem, Absorica, Zenatane, Myorisan)

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This agent is the most active among retinoids. This form of therapy is not generally accepted as standard therapy.

Hematopoietic Growth Factors

Class Summary

Ineffective blood cell production is due to excess cellular apoptosis (programmed cell death) caused by activation of the Fas-Fas ligand. Hematopoietic growth factors are capable of reversing this process to some extent.

Epoetin alfa (Procrit, Epogen)

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Epoetin alfa is a glycoprotein that stimulates red blood cell (RBC) production by stimulating division and maturation of committed RBC precursor cells. It is effective in 20-26% of MDS patients when administered alone and in as many as 48% of patients when combined with granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF).

Darbepoetin (Aranesp)

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Darbepoetin is an erythropoiesis-stimulating protein closely related to erythropoietin, a primary growth factor that is produced in the kidney and stimulates development of erythroid progenitor cells in bone marrow. This agent's mechanism of action is similar to that of endogenous erythropoietin, which interacts with stem cells to increase red cell production.

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Darbepoetin differs from epoetin alfa (recombinant human erythropoietin) in containing 5 N-linked oligosaccharide chains, whereas epoetin alfa contains 3. Darbepoetin has a longer half-life than epoetin alfa, and may be administered weekly or biweekly.

Sargramostim (Leukine)

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This GM-CSF stimulates division and maturation of earlier myeloid and macrophage precursor cells. It has been reported to increase granulocytes in 48-91% of patients with MDS.

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Filgrastim (Neupogen, Granix)

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This G-CSF stimulates division and maturation of granulocytes, mostly neutrophils, in 75-100% of MDS patients and seems to enhance erythroid response when given in combination with erythropoietin.

Antineoplastic Agent, Methylation Inhibitors

Class Summary

Demethylation agents are a ntineoplastics that exert anticancer effects by causing DNA demethylation or hypomethylation in abnormal hematopoietic bone marrow cells. These agents may restore normal function to the tumor suppressor genes responsible for regulating cell differentiation and growth.

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Azacitidine (Vidaza)

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Azacitidine is a pyrimidine nucleoside analogue of cytidine. It interferes with nucleic acid metabolism. It exerts antineoplastic effects by DNA hypomethylation and direct cytotoxicity on abnormal hematopoietic bone marrow cells. Nonproliferative cells are largely insensitive to azacitidine. This agent is approved by the US Food and Drug Administration for treatment of all 5 MDS subtypes.

Decitabine (Dacogen)

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Decitabine is a hypomethylating agent believed to exert antineoplastic effects by incorporating into DNA and inhibiting methyltransferase, resulting in hypomethylation. Hypomethylation in neoplastic cells may restore normal function to genes that are critical for cellular control of differentiation and proliferation.

Decitabine is indicated for treatment of MDSs, including previously treated and untreated, de novo, and secondary MDSs of all French-American-British (FAB) subtypes (ie, refractory anemia, refractory anemia with ringed sideroblasts, refractory anemia with excess blasts, refractory anemia with excess blasts in transformation, chronic myelomonocytic leukemia) and International Prognostic Scoring System (IPSS) groups intermediate-1 risk, intermediate-2 risk, and high risk.

Immunomodulators

Class Summary

Immunomodulators elicit immunomodulatory, antiangiogenic properties, and inhibit proinflammatory cytokines.

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Lenalidomide (Revlimid)

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Lenalidomide is indicated for the transfusion-dependent MDS subtype of deletion 5q cytogenetic abnormality. This agent is structurally similar to thalidomide. It elicits immunomodulatory and antiangiogenic properties, inhibits proinflammatory cytokine secretion, and increases release of anti-inflammatory cytokines from peripheral blood mononuclear cells. The dose used in MDS is much lower than that used for multiple myeloma.

Antineoplastic agents, Miscellaneous

Class Summary

Agents in this class inhibit cell growth and proliferation.

Arsenic trioxide (Trisenox)

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May cause DNA fragmentation and damage or degrade the fusion protein PML-RAR alpha. Use only in patients that have relapsed or are refractory to retinoid or anthracycline chemotherapy.

Erythroid Maturation Agents

Class Summary

These agents promote erythroid maturation by antagonizing inhibitors of late-stage erythropoiesis.

Luspatercept (Luspatercept-aamt, Reblozyl)

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Indicated for treatment of anemia failing an ESA and requiring 2 or more red blood cell (RBC) units over 8 weeks in adult patients with very low- to intermediate-risk myelodysplastic syndromes with ring sideroblasts (MDS-RS) or with myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T). It is not a substitute for RBC transfusions in patients who require immediate correction of anemia

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Myelodysplastic Syndrome