What is Myelodysplastic Syndrome - Excess Blasts (MDS-EB)

From the Guidelines

MDS-EB (Myelodysplastic Syndrome with Excess Blasts) is a type of blood cancer characterized by an increased number of immature blood cells (blasts) in the bone marrow, with blast percentages between 5-19% in the bone marrow or 2-19% in the peripheral blood, as defined by the WHO classification 1. MDS-EB is a more aggressive form of myelodysplastic syndrome, divided into two subtypes: MDS-EB1 (5-9% blasts in bone marrow or 2-4% in blood) and MDS-EB2 (10-19% blasts in bone marrow or 5-19% in blood) 1.

Key Characteristics of MDS-EB

• Increased number of immature blood cells (blasts) in the bone marrow
• Blast percentages between 5-19% in the bone marrow or 2-19% in the peripheral blood
• Divided into two subtypes: MDS-EB1 and MDS-EB2

Treatment Options for MDS-EB

• Supportive care with blood transfusions and growth factors
• Hypomethylating agents like azacitidine (75 mg/m² for 7 days every 28 days) or decitabine (20 mg/m² for 5 days every 28 days) 1
• Consideration for allogeneic stem cell transplantation in eligible patients

Prognosis and Disease Course

• The prognosis is generally poor without treatment, with a higher risk of progression to acute myeloid leukemia compared to other MDS subtypes 1
• The disease results from genetic mutations in hematopoietic stem cells that disrupt normal blood cell development, leading to cytopenias (low blood counts) and an accumulation of abnormal blast cells 1

From the FDA Drug Label

Azacitidine for injection is indicated for treatment of adult patients with the following French-American- British (FAB) myelodysplastic syndrome subtypes: refractory anemia (RA) or refractory anemia with ringed sideroblasts (if accompanied by neutropenia or thrombocytopenia or requiring transfusions), refractory anemia with excess blasts (RAEB), refractory anemia with excess blasts in transformation (RAEB-T), and chronic myelomonocytic leukemia (CMMoL) 2 Decitabine for injection is a nucleoside metabolic inhibitor indicated for treatment of adult patients with myelodysplastic syndromes (MDS) including previously treated and untreated, de novo and secondary MDS of all French-American-British subtypes (refractory anemia, refractory anemia with ringed sideroblasts, refractory anemia with excess blasts, refractory anemia with excess blasts in transformation , and chronic myelomonocytic leukemia) and intermediate-1, intermediate-2, and high-risk International Prognostic Scoring System groups 3

Myelodysplastic Syndrome - Excess Blasts (MDS-EB) is also known as Refractory Anemia with Excess Blasts (RAEB). It is a subtype of myelodysplastic syndrome characterized by an excess of blasts in the bone marrow or blood. The exact definition of MDS-EB is not provided in the drug labels, but it is mentioned as one of the subtypes of myelodysplastic syndromes for which azacitidine and decitabine are indicated.

• Key characteristics: excess blasts in the bone marrow or blood
• Treatment: azacitidine and decitabine are indicated for treatment of adult patients with MDS-EB (RAEB) 2 3

From the Research

Definition and Characteristics of Myelodysplastic Syndrome - Excess Blasts (MDS-EB)

• Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal hematopoietic malignancies characterized by morphologic bone marrow dysplasia, anemia, neutropenia, or thrombocytopenia, and an increased risk of acute myeloid leukemia (AML) 4.
• MDS-EB is a subtype of MDS characterized by an excess of blasts in the bone marrow, which increases the risk of transformation to AML.
• The diagnosis of MDS is based on morphological evidence of dysplasia upon visual examination of a bone marrow aspirate and biopsy, and is often complemented by additional studies such as karyotype, flow cytometry, and molecular genetics 5, 6.

Risk Stratification and Prognosis

• The prognosis of patients with MDS can be calculated using various scoring systems, including the Revised International Prognostic Scoring System (IPSS-R), which takes into account peripheral cytopenias, percentage of blasts in the bone marrow, and cytogenetic characteristics 5, 6.
• Somatic mutations can also help define prognosis and guide therapy 6.
• Patients with MDS-EB are considered to be at higher risk of transformation to AML and have a poorer prognosis compared to those with lower-risk MDS subtypes.

Treatment Options

• Treatment options for MDS-EB include hypomethylating agents such as azacitidine and decitabine, which have been shown to improve survival in higher-risk MDS patients 4, 7.
• Intensive chemotherapy and allogeneic stem cell transplantation are also considered for higher-risk patients, and may offer a potential cure 4, 8.
• Novel therapeutics, such as luspatercept and oral hypomethylating agents, are also being explored for the treatment of MDS-EB 6.