MYELODYSPLASTIC SYNDROME (MDS)

DEFINITION & PATHOPHYSIOLOGY

MDS is a group of clonal bone marrow disorders characterized by ineffective hematopoiesis, dysplasia in one or more myeloid cell lines, peripheral cytopenias, and potential progression to AML in approximately 20–30% of cases. MDS is considered a form of blood cancer. The four key pathophysiologic mechanisms are: maturation arrest, ineffective hematopoiesis, increased apoptosis of hematopoietic precursors, and immunological abnormalities. Apoptosis is more prominent in early MDS, while maturation block dominates as the disease transforms toward leukemia.

CAUSES AND RISK FACTORS

MDS may be primary (de novo, idiopathic) or secondary. Secondary MDS arises from prior chemotherapy (alkylating agents, topoisomerase II inhibitors), radiation therapy, environmental toxin exposure (e.g., benzene), or inherited bone marrow failure syndromes (e.g., Fanconi anemia, Diamond-Blackfan anemia). MDS primarily affects adults over 60 years of age. Genetic mutations frequently involved include TP53, TET2, ASXL1, SF3B1, and DNMT3A.

CLINICAL PRESENTATION

Symptoms result from cytopenias: fatigue and pallor from anemia, recurrent infections and fever from neutropenia, and bleeding, bruising, or petechiae from thrombocytopenia. Some patients are completely asymptomatic at diagnosis.

DIAGNOSIS

Diagnosis requires integration of the following:

• CBC with differential
• Peripheral smear: dysplastic features such as hypogranular neutrophils and oval macrocytes
• Bone marrow biopsy: dysplasia in one or more myeloid lineages and blast count below 20%
• Cytogenetics: common abnormalities include del(5q), del(7q), monosomy 7, trisomy 8, and complex karyotypes
• Molecular studies: assess mutations for prognostication and targeted therapy

Risk stratification uses the IPSS-R (Revised International Prognostic Scoring System).

RISK STRATIFICATION (IPSS-R)

TREATMENT: LOW-RISK MDS

First-line treatment is chosen based on clinical scenario:

Key rules for low-risk MDS:

• Lenalidomide is only appropriate if del(5q) is confirmed — it is less effective or potentially harmful without this abnormality. In a Phase II study, 83% of del(5q) patients responded vs. 57% with normal karyotype.
• Luspatercept is a TGF-β ligand trap that promotes late-stage erythroid maturation; it is used after ESA failure in patients with ring sideroblasts.
• Immunosuppressive therapy (ATG + cyclosporine) is best for patients under 60 years old, with hypocellular marrow, HLA-DR15 positive, or PNH clones; response rate is ~30–40%.
• Decitabine and azacitidine are NOT used in low-risk MDS unless all other agents have failed.
• Allogeneic SCT is NOT standard for low-risk MDS.
• G-CSF alone is not clearly indicated; it may be used to augment ESA response.

• Eltrombopag has no established role in MDS.TREATMENT: HIGH-RISK MDS

First-line: Hypomethylating agents (HMAs)

• Azacitidine (preferred): SubQ or IV for 7 days every 28 days; proven to improve overall survival in the AZA-001 trial. Decitabine: IV over 5 days; alternative when azacitidine is not tolerated.
• Mechanism: Both are DNA methyltransferase inhibitors that reverse abnormal gene silencing, restoring normal cell differentiation and survival.
• CRITICAL: A minimum of 4–6 cycles must be completed before declaring treatment failure, as responses may be delayed. Continue in the absence of progression or unacceptable toxicity.
• Allogeneic HSCT is the only potentially curative option. Eligibility criteria: ECOG performance status ≤ 2, IPSS-R intermediate-2 or high-risk, available donor, and minimal comorbidities assessed by the HCT-CI index. Allo-HSCT provides superior overall survival compared to chemotherapy in high-risk MDS.
• No role for radiation therapy or autologous HSCT in MDS. Autologous HSCT is contraindicated because the diseased marrow produces inadequate stem cells to collect.

HMA-refractory disease options (in order of preference):

• Clinical trials (first recommendation)
• Venetoclax + azacitidine
• IDH1/2 inhibitors if mutation is present
• Palliative and supportive care

FULL TREATMENT SUMMARY BY RISK GROUP

TARGETED THERAPIES AND MUTATIONS

ANEMIA MANAGEMENT AND SUPPORTIVE CARE

RBC transfusions are used as needed. ESAs (epoetin alfa or darbepoetin alfa) are used in low-risk MDS with symptomatic anemia when EPO is below 500 mU/mL and transfusion burden is low.

Iron chelation therapy: Start when ferritin exceeds 1000 ng/mL, transfusion burden reaches 20–25 RBC units, and expected survival is greater than 1 year. Agents: deferasirox (oral) or deferoxamine (IV/SubQ). Discontinue exogenous iron supplements and ascorbic acid (ascorbic acid increases iron absorption and should be stopped in transfusion-related iron overload). Signs of iron overload: dyspnea and abdominal pain with elevated ferritin in heavily transfused patients.

HMA TOXICITY MONITORING

Myelosuppression: Monitor CBC weekly during early cycles. Hold therapy if ANC falls below 0.5 x 10⁹/L or platelets fall below 25 x 10⁹/L. G-CSF may be used selectively for neutropenic fever. GI effects: nausea, vomiting, and constipation — manage with prophylactic antiemetics such as ondansetron. Injection site reactions: rotate sites and use topical corticosteroids if needed.

RESPONSE ASSESSMENT (IWG CRITERIA)

Treatment response in MDS is evaluated across all four of the following dimensions:

• Hematologic improvement (HI): improved hemoglobin, platelets, or ANC
• Complete remission (CR): normal counts, less than 5% marrow blasts, no dysplasia
• Partial remission (PR): at least 50% reduction in blast percentage
• Cytogenetic response and alteration of disease progression and quality of life

MDS vs. APLASTIC ANEMIA

HIGH-YIELD EXAM PEARLS

• Diagnosis: MDS is a clonal bone marrow disorder with ineffective hematopoiesis and dysplasia in one or more myeloid lines. Diagnose with CBC, bone marrow biopsy, cytogenetics, and molecular studies. Common cytogenetic abnormalities: del(5q), del(7q), monosomy 7, trisomy 8, complex karyotype.
• Low-risk treatment decision tree: EPO < 500 and low transfusion burden → ESA ± G-CSF. Del(5q) → lenalidomide. Ring sideroblasts + SF3B1 + EPO > 500 or ESA failure → luspatercept. Hypoplastic MDS → ATG + cyclosporine (NOT epoetin). Lenalidomide only if del(5q) confirmed — do not use without it.
• High-risk treatment: First-line → azacitidine (preferred HMA). Minimum 4–6 cycles before declaring failure. Only curative option → allogeneic HSCT. HMA-refractory → clinical trial first, then venetoclax + azacitidine or IDH inhibitors.
• Iron overload: Ferritin > 1000 + ≥ 20–25 transfusions + survival > 1 year → start iron chelation. Stop iron supplements and ascorbic acid. Use deferasirox (oral) or deferoxamine (IV/SubQ).
• ATO and transplant rules: No role for radiation or autologous HSCT in MDS. Allo-HSCT reserved for high-risk disease only. Eltrombopag has no established role in MDS.
• Key mutations: TP53 = complex karyotype, poor prognosis, therapy-resistant. IDH1 → ivosidenib. IDH2 → enasidenib. SF3B1 → luspatercept.
• Prognosis: Low-risk → median survival > 5 years. High-risk → median survival ~1–2 years (as low as 4–8 months in IPSS-defined high-risk). Risk predicted by WBC + platelets + blast % + cytogenetics.
• Response assessment uses all four IWG criteria: hematologic improvement, cytogenetic response, disease progression, and quality of life.

1. What is Myelodysplastic Syndrome (MDS)?

MDS is a group of clonal bone marrow disorders characterized by ineffective hematopoiesis, dysplasia in one or more myeloid cell lines, peripheral cytopenias, and potential progression to acute myeloid leukemia (AML)"

2. What causes MDS?

MDS may arise de novo or secondary to prior chemotherapy, radiation, or environmental toxin exposure (e.g., benzene). It can also be linked to inherited bone marrow failure syndromes

3. Who is at risk for developing MDS?

Primarily older adults (>60 years), patients previously treated with chemotherapy or radiation, and those with certain genetic predispositions or chronic exposure to toxins

4. What are the common symptoms of MDS?

Symptoms are often due to low blood counts and include fatigue (anemia), infections (neutropenia), and bleeding or bruising (thrombocytopenia). Some patients are asymptomatic at diagnosis

 5. How is MDS diagnosed?

• CBC with differential
• Bone marrow biopsy (to assess dysplasia and blast count)
• Cytogenetic and molecular studies (to identify chromosomal or gene mutations)

6. What cytogenetic abnormalities are common in MDS?

Common abnormalities include del(5q), del(7q), monosomy 7, trisomy 8, and complex karyotypes. These findings help in risk stratification and treatment decisions

Can MDS progress to leukemia?

Yes. Around 20–30% of patients with MDS will progress to acute myeloid leukemia (AML), especially those with high-risk features. 

Is MDS a type of cancer?

Yes. MDS is considered a form of blood cancer originating from the bone marrow, though it behaves differently from acute leukemias". 

9. What is the difference between low-risk and high-risk MDS?

Answer:
- Low-risk MDS: fewer cytopenias, lower blast count (<5%), favorable cytogenetics
- High-risk MDS: multiple cytopenias, higher blasts (5–19%), poor-risk cytogenetics (e.g., complex karyotype) 

What are the treatment options for low-risk MDS?

1. Supportive care (e.g., transfusions, erythropoiesis-stimulating agents like EPO)
2. Lenalidomide (especially in del(5q) MDS)
3. Immunosuppressive therapy (e.g., ATG + cyclosporine in selected patients). 

12. What are the treatment options for high-risk MDS?

1. Hypomethylating agents: azacitidine or decitabine
2. Allogeneic stem cell transplant (HSCT) – the only potential cure
3. Clinical trials for targeted therapies and novel agents

What are hypomethylating agents, and how do they work?

Azacitidine and decitabine are DNA methyltransferase inhibitors that reverse abnormal gene silencing, improving cell differentiation and survival.. 

Both are hypomethylating agents (HMAs) with similar mechanisms
1. Azacitidine (preferred): SubQ or IV for 7 days every 28 days; improves overall survival in high-risk MDS (AZA-001 trial)
2. Decitabine: IV over 5 days; more commonly used in AML or in patients unable to tolerate azacitidine

Is lenalidomide used in all types of MDS?

No. Lenalidomide is most effective in patients with isolated del(5q) and low-risk MDS. It is less effective or potentially harmful in patients without this cytogenetic abnormality.. 

15. What role does HSCT (stem cell transplant) play in MDS?

Allogeneic HSCT is potentially curative but is usually limited to younger or fit older patients with high-risk disease due to associated morbidity and mortality. 

16. How is anemia managed in MDS?

Management includes:
1. RBC transfusions
2. Erythropoiesis-stimulating agents (e.g., epoetin alfa, darbepoetin)
3. Lenalidomide (for del(5q))
4. Iron chelation therapy in patients with iron overload 

17. Can MDS patients develop iron overload?

Yes. Chronic RBC transfusions can cause secondary iron overload, increasing the risk of organ damage. Iron chelation therapy (e.g., deferasirox) may be indicated

18. What is the prognosis for MDS patients?

Prognosis depends on IPSS-R risk group:
1. Low-risk: Median survival >5 years
2. High-risk: Median survival ~1–2 years; higher chance of AML transformation 

19. Are there targeted therapies for MDS?

Yes, targeted therapies are used in MDS, primarily directed at specific cytogenetic abnormalities or signaling pathways.

Key targeted agents for MDS include:

• Lenalidomide: Specifically targets patients with the del(5q) chromosomal abnormality. It is particularly effective for symptomatic anemia in lower-risk disease and can induce cytogenetic responses.
• Luspatercept: A first-in-class recombinant fusion protein. It is indicated for patients with lower-risk MDS with ring sideroblasts who have failed or are unlikely to respond to erythropoiesis-stimulating agents (ESAs).
• Ivosidenib: An IDH1 inhibitor that is FDA-approved for adults with relapsed or refractory (R/R) MDS carrying an IDH1 mutation.
• Hypomethylating Agents (Azacitidine, Decitabine): While sometimes considered broad chemotherapy, they specifically target epigenetic modifiers by inhibiting DNA methyltransferase to restore normal gene expression.

20. Can MDS be cured?

The only potentially curative treatment is allogeneic HSCT. Otherwise, most therapies are palliative or disease-modifying, aiming to improve quality of life and delay progression. 

22. What are the key side effects of azacitidine, and how are they managed?

1. Myelosuppression (common): Monitor CBC weekly during early cycles; may require dose delays or growth factor support
2. GI effects: Nausea, vomiting, constipation—prophylactic antiemetics (e.g., ondansetron) recommended
3. Injection site reactions: Rotate sites, use topical corticosteroids if needed 

23. What mutations are targetable in MDS, and how are they treated?

1. SF3B1: Associated with ring sideroblasts; patients may benefit from luspatercept
2. IDH1/IDH2: Investigational use of ivosidenib (IDH1) or enasidenib (IDH2) in refractory MDS
3. TP53 mutations: Poor prognosis; investigational use of APR-246 (eprenetapopt) in combination with azacitidine 

24. What is luspatercept, and when is it used in MDS?

Luspatercept is a TGF-β superfamily ligand trap that promotes late-stage erythroid maturation. Approved for lower-risk MDS with ring sideroblasts and transfusion-dependent anemia who have failed ESA therapy.

When is immunosuppressive therapy appropriate in MDS?

In younger (<60 yrs), hypocellular MDS, HLA-DR15 positive, or patients with PNH clones. Treatment: Anti-thymocyte globulin (ATG) + cyclosporine; response rate ~30–40% 

28. What clinical factors determine eligibility for allogeneic stem cell transplant in MDS?

• Age & performance status (ECOG ≤2)
• IPSS-R risk group (generally intermediate-2 or high-risk)
• Donor availability
• Minimal comorbidities (assessed using HCT-CI index) 

When should iron chelation therapy be initiated in MDS patients?

Start in:

• Low-risk MDS patients with expected survival >1 year
• Transfusion burden ≥20–25 RBC units
• Serum ferritin >1000 ng/mL
• Agents: Deferasirox (oral), deferoxamine (IV/subQ) 

29. How is treatment response assessed in MDS?

Response criteria are defined by the International Working Group (IWG):

• Hematologic improvement (HI): Improved hemoglobin, platelets, ANC
• Complete remission (CR): Normal counts, <5% marrow blasts, no dysplasia
• Partial remission (PR): ≥50% reduction in blast percentage 

30. What are treatment options for HMA-refractory high-risk MDS?

• Clinical trials (first-line recommendation)
• Venetoclax-based regimens (e.g., venetoclax + azacitidine)
• Targeted agents (IDH1/2 inhibitors if mutations present)
• Palliative care/transfusions/supportive management 

31. How do you monitor and manage cytopenias during HMA therapy?

• Baseline and serial CBC (every 1–2 weeks during early cycles)
• Hold or delay therapy if ANC < 0.5 x10⁹/L or platelets < 25 x10⁹/L
• Growth factors (e.g., G-CSF) may be used selectively in neutropenic fever 

32. How many cycles of HMA therapy are needed before assessing response?

A minimum of 4–6 cycles is recommended before declaring treatment failure, as responses may be delayed. Continue in the absence of progression or unacceptable toxicity.

What is the difference between MDS and aplastic anemia?

MDS: Clonal disorder with dysplasia and risk of AML
Aplastic anemia: Immune-mediated marrow failure with hypocellularity but no dysplasia or clonal evolution (unless overlapping with PNH or evolves to MDS) 

35. What is the significance of TP53 mutations in MDS

TP53 mutations are associated with

• Complex karyotypes
• Poor prognosis
• Resistance to conventional therapy
• Patients may benefit from clinical trials (e.g., APR-246 + azacitidine)

26. What is the role of erythropoiesis-stimulating agents (ESAs) in MDS?

Used in low-risk MDS with symptomatic anemia. Best response in:

• 1. Serum EPO < 500 mU/mL
• 2. Low transfusion burden
• 3. Agents: Epoetin alfa, darbepoetin alfa

While awaiting cytogenetic analysis of a bone marrow sample from an MDS patient, your collaborating physician asks you if there is an oral option available to treat MDS. Lenalidomide is an option. However, lenalidomide is most appropriate in an MDS patient with which of the following cytogenetic features?

• A. Del(12p)
• B. Del(5q)
• C. FLT3-ITD
• D. Normal Cytogenetics

Answer: Del(5q) (B) is the correct answer.

In a Phase II study, patients who received lenalidomide and had a deletion of 5q benefited most from lenalidomide. In total, 83% of patients with del(5q) had response vs. 57% with a normal karyotype vs. 12% with other cytogenetic abnormalities (p=0.007). Thus the best answer would be del(5q). FLT3-ITD mutations respond to FLT3 inhibitors, not lenalidomide. Additionally, FLT3 inhibitors have been approved for acute myeloid leukemia, not for MDS.

TK is a 72-year-old male with multiple comorbidities, including diabetes, hypertension, atrial fibrillation, and low-grade MDS. He is currently being treated with best supportive care due to a PS of 3 and consequently has received more than 30 blood transfusions in addition to daily iron supplementation. He presents with complaints of shortness of breath and abdominal pain. His labs are as follows:

WBC 3300 cells/mm³ with 45% neutrophils, hemoglobin 9 gm/dL, platelets 121,000 cells/mm³, serum creatinine 1.1 mg/dL, total bilirubin 0.8 mg/dL, ferritin 3100 ng/ml.

Which of the following is the most likely cause of TK’s current symptoms?

• A. Untreated iron overload
• B. Invasive pulmonary aspergillosis
• C. Sinusoidal obstructive syndrome
• D. Adverse drug reaction to iron supplements

Answer: The correct answer is A (untreated iron overload).

• Best supportive care for low-grade MDS includes support with red blood cell transfusion. TK’s signs and symptoms suggest iron overload, which is a potential problem with repeated red blood cell transfusions. Thus, the correct answer is A. TK should be started on iron chelation therapy such as deferoxamine or deferasirox. Additionally, exogenous sources of iron, such as iron supplements, should be discontinued.
• Lastly, ascorbic acid increases the absorption of iron and should also be discontinued.
• Answer B is incorrect because, despite having MDS, this patient’s neutrophil count is preserved, thus not at high risk for invasive aspergillus. Additionally, no other diagnostic information was given to confirm invasive aspergillus infection (i.e., CT scan, galactomannan, or histopathological/culture data).
• Answer C is incorrect as no information was given to suggest sinusoidal obstructive syndrome (i.e., significant weight gain, hyperbilirubinemia, hepatomegaly, etc.).
• Answer D is incorrect because TK’s symptoms would not be an adverse reaction to the oral iron replacement, which would not lead to iron overload when taken in normal amounts.

37. Pathophysiology of MDS involves:

• a. Maturation arrest
• b. Ineffective hematopoiesis
• c. Increased apoptosis
• d. Immunological abnormalities
• e. All of the above

Answer: e. All of the above

The correct answer is e. All of the above.

Rationale

• Ineffective Hematopoiesis: MDS is fundamentally defined as a group of diseases characterized by ineffective hematopoiesis, where the bone marrow fails to produce enough functional blood cells.
• Increased Apoptosis: A key driver of the resulting cytopenias is the over-activation of pathways (such as the TGF-β superfamily) that lead to the transcription of apoptotic proteins, causing premature cell death,.
• Maturation Arrest: The sources describe MDS as a problem with the growth and synthesis of myeloid cells, where dysplastic changes prevent cells from maturing into functional neutrophils or RBCs,.
• Immunological Abnormalities: The clinical success of immunosuppressive therapies (like ATG and cyclosporine) in about 30% of patients confirms that underlying immune-mediated destruction of stem cells is part of the disease process,.

38. The median survival for high-risk MDS is:

• a. 4–8 months
• b. 1–2 years
• c. 2–4 years
• d. 4–6 years

Answer: a. 4–8 months

The correct answer is b. 1–2 years.

Rationale

• Trial Data: Clinical trials for higher-risk MDS patients show median overall survival (OS) typically falls within the 1-to-2-year range. 
• Supportive Care Outcomes: Other cooperative group trials in higher-risk populations have shown median survival times as low as 11 to 18 months depending on the intervention.
• Prognostic Context: These outcomes underscore why higher-risk MDS is often managed more aggressively, with allogeneic hematopoietic cell transplantation (HCT) as the only curative goal for eligible patients.

39. Response to MDS treatment is assessed by:

• a. Hematological improvement
• b. Cytogenetic improvement
• c. Alteration of disease progression
• d. Quality of life
• e. All of the above

Answer: e. All of the above

The International Working Group criteria define four specific aspects of responses based on treatment goals: hematological improvement, cytogenetic improvement, alteration of disease progression, and quality of life. Hematological improvement is scored for each lineage according to whether there is a major or minor response, while cytogenetic improvement is scored according to whether there is a partial or complete response. Alteration of the natural course of the disease is determined according to various measures of disease progression and survival.

40. Treatment for low-risk MDS include, all except:

• a. Erythropoietin
• b. G-CSF
• c. Lenalidomide
• d. Reduced intensity allo-SCT

Answer: d. Reduced intensity allo-SCT

The treatment for low-risk MDS includes all the options listed except d. Reduced intensity allo-SCT.

Rationale

• Lower-Risk Therapy: Treatment for patients with lower-risk MDS focuses on managing symptomatic cytopenias (primarily anemia). Standard options include erythropoietin (ESAs), G-CSF (used to enhance the response to ESAs), and lenalidomide (specifically for those with the del(5q) mutation).
• Allo-SCT: While allogeneic hematopoietic cell transplantation (HCT) is the only curative treatment for MDS, it is generally reserved for patients with higher-risk disease who have a high probability of progressing to AML.
• Decision Markers: The standard algorithm for lower-risk MDS focuses on transfusion needs, serum erythropoietin levels, and specific mutations rather than immediate transplant.

JN is a 59-year-old female who was recently diagnosed with MDS. The diagnostic work-up revealed her MDS IPSS score to be 25. JN has four siblings: three sisters and one brother. She has normal chemistry values on her recent lab tests. JN has required red blood cell transfusions every week over the past few weeks.

Which of the following is the best course of therapy for JN.

• A. Radiation to the hip (1%)
• B. Autologous HSCT (12%)
• C. Chemotherapy (16%)
• D. Allogeneic HSCT (71%)

Answer D:

The last answer is the best answer choice as an allogeneic HSCT is indicated for patients with a diagnosis of myelodysplastic syndrome. This is a liquid tumor, and radiation has no role in the treatment. Radiation to the hip may actually worsen MDS. Autologous HSCT is not a good option as MDS is a bone marrow disease. In addition, there are inadequate stem cells to collect as marrow is already unable to produce adequate marrow cells. Chemotherapy can be considered in patients with MDS. Allogeneic HSCT provides higher overall survival in patients with high-risk IPSS-high-risk MDS compared with chemotherapy. Chemotherapy is a good option in patients with low-risk MDS. Chemotherapy can be considered in patients with high-risk MDS and HSCT ineligibility. These patients could be elderly or patients without any close match.

According to the NCCN guidelines, which of the following patients is receiving the most appropriate therapy for their MDS?

• A. A 73-year-old male with newly diagnosed lower-risk MDS with a del5q mutation and anemia receiving azacitidine
• B. A 67-year-old female with higher risk MDS with 12% blasts receiving luspatercept
• C. A 58-year-old male with newly diagnosed hypoplastic MDS receiving epoetin
• D. A 61-year-old female with newly diagnosed higher-risk MDS undergoing an allogeneic cell transplantation

Answer: D. A 61-year-old female with newly diagnosed higher risk MDS undergoing an allogeneic cell transplantation

Correct answer = D

• A) Patients with del5q should receive lenalidomide; azacitidine should be reserved for patients with higher risk MDS or if multi-lineage cytopenias are present in lower risk MDS.
• B) Patients with higher risk MDS should receive a hypomethylating agent (or go directly to an allo-transplant if eligible and/or after debulking from an HMA), not luspatercept.
• C) Hypoplastic MDS should be treated similarly to aplastic anemia: ie IST. Epoetin is not appropriate.
• D) The standard of care for higher-risk MDS is an allo-HCT if young/fit/eligible.