What is My Risk Status and Type of MDS?

Myelodysplastic syndrome (MDS) is different from other cancers because it does not grow in one spot to form a tumor. Because of this, MDS has to be classified differently than many other types of cancers.

How is Risk Status Assessed in MDS?

Risk status helps predict whether MDS will respond well to treatment or progress into a more aggressive disease like acute myeloid leukemia (AML). Specialists have created an MDS classification system based on the different risk factors associated with the disease. Two main systems are currently used to categorize patients based on prognosis: the International Prognostic Scoring System- Revised (IPSS-R) and the WHO Prognostic Scoring System (WPSS).

International Prognostic Scoring System- Revised (IPSS-R)

This system is based on people diagnosed many years ago who did not receive treatment for their MDS. Patients are categorized based on several factors: red blood cell count, white blood cell count, platelet count, percentage of blasts in the bone marrow, and the number and type of chromosome abnormalities. Scores for the IPSS-R are broken into 5 categories:

IPSS-R Risk	Median Survival
Very low	8.8 years
Low	5.3 years
Intermediate	3 years
High	1.6 years
Very high	0.8 years

To know more about high- and very high-risk MDS we have a comprehensive article here. 

WHO Prognostic Scoring System (WPSS)

This system used to determine MDS Survival. It is important to note that this system does not include MDS patients with secondary MDS (MDS caused by chemotherapy use). 

Patients are categorized based on several factors: MDS type, whether or not they need regular blood transfusions and chromosomal abnormalities.  

WPSS Risk	Median Survival
Very Low	11.8 years
Low	5.5 years
Intermediate	4 years
High	2.2 years
Very High	9 months

What's the Difference Between Primary and Secondary MDS? 

MDS risk status can be classified in several ways. One way to classify a patient's risk status is as primary or secondary related to the cause of MDS. MDS is diagnosed as primary when we can’t find a cause and as secondary when we do know the cause. 

What are the Phases of MDS? 

MDS can be divided into three phases: early, advanced, and final. This describes the way MDS progresses. 

• Early phase: patients may have few or no symptoms, and the disease may be discovered through routine blood tests.
• Advanced phase: symptoms become more noticeable and may include fatigue, shortness of breath, frequent infections, and easy bruising or bleeding.
• Final phase: This happens when MDS evolves into acute myeloid leukemia (AML), a fast-growing cancer of the bone marrow cells. Not all people with MDS will progress to AML, but patients with high-risk MDS status might be more likely to evolve. 

What are the MDS Types?

The WHO has a system for classifying different types of MDS mainly differentiated by the appearance of the bone marrow cells under the microscope. There are other factors that also help to differentiate between the different types of MDS: how many blasts (immature stem cells) look abnormal, how many types of cells have low counts, percentage of blasts in the bone marrow, how many blood cells are ring sideroblasts, and which chromosomes exhibit changes in the bone marrow. 

MDS With Multilineage Dysplasia (MDS-MLD)

This is the most common type of MDS. Someone with MDS-MLD has low counts of at least one blood type, less than 5% of stem cells in the bone marrow are immature stem cells (blasts), blasts are rarely found in the blood, and there is at least 10% of 2 or 3 cell types that look abnormal in the bone marrow. 

MDS With Single Lineage Dysplasia (MDS-SLD)

Someone with MDS-SLD has low counts of at least one blood type, less than 5% of stem cells in the bone marrow are blasts, blasts are rarely found in the blood, and there is at least 10% in only 1 cell type that looks abnormal in the bone marrow. 

MDS With Excess Blasts (MDS-EB)

Someone with MDS-EB has more blasts in their bone marrow and blood than normal and has low counts of at least one blood type. Cells may or may not appear abnormal. This type of MDS is the most likely to turn into AML.

There are two subtypes of MDS-EB. These subtypes are determined by how many blasts are present in the bone marrow or blood. 

MDS-EB1 

5-9% of the cells in the bone marrow are blasts or 2-4% in the blood.

MDS-EB2

10-19% of the cells in the bone marrow are blasts or 5-19% of cells in the blood.

MDS With Ring Sideroblasts (MDS-RS)

Someone with MDS-RS has ring sideroblasts for at least 15% of their immature red blood cells. If there is a mutation in the SF3B1 gene, this percentage is lower at only 5% needed for the diagnosis. This is a rare form of MDS and will rarely turn into AML. Patients with this type of MDS generally have better outcomes than other types of MDS.

There are two subtypes of MDS-RS. These subtypes are determined by how many types of cells in their bone marrow appear abnormal.

MDS-RS with Single Lineage Dysplasia (MDS-RS-SLD) 

Only one cell type appears abnormal

MDS-RS- with Multilineage Dysplasia (MDS-RS-MLD)

More than one cell type appears abnormal

MDS With Isolated del(5q)

Someone with this type of MDS is missing part of chromosome 5 in their bone marrow cells, low counts of 1 or 2 blood cell types, and at least 1 cell type that appears abnormal. This is a rare form of MDS as it is most commonly diagnosed in older women, who make up only a small portion of MDS patients. This type rarely turns into AML and generally has better outcomes than other types of MDS.

MDS, Unclassifiable (MDS-U)

Someone with this type of MDS doesn’t fit in any other MDS type. This type is uncommon, and isn’t very well understood yet. 

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