Understanding Myelodysplastic Syndrome's Nature as Cancer

Experts consider the nature of myelodysplastic syndrome and highlight factors that differentiate it from other cancers.


Bart Scott, MD, MS: Is MDS [myelodysplastic syndrome] really a cancer, and how does it relate to other cancers? It is considered to be a cancer. Beginning in about 2001, its diagnostic code was changed to a cancer, and therefore its data were captured in what we call the SEER [Surveillance, Epidemiology, and End Results] Registry data. We typically think of cancer as being this bad prognostic disease, and patients quickly progress and have a short survival. Myelodysplastic syndromes are a group of disorders, so it’s not just 1 type of disease. It’s many different types of disease that we group together. They have this clonal hematopoiesis, cytopenias, risk of progression to AML [acute myeloid leukemia], and share in common some abnormal findings within the bone marrow what we call dysplasia, which stands for abnormal growth.

The distinction between what most people consider to be cancer is that some patients with MDS may have a relatively good quality of life with not a lot of pain. They may have very mild symptoms or no symptoms at all. When they hear the word cancer and what it carries with it, the emotional baggage and such, they think that doesn’t describe how they feel or what’s going on in their body. It’s important to remember that MDS is a group of disorders that are interrelated, but it’s not necessarily a single disease. There are some patients with MDS who do more rapidly progress and have more symptoms.

Amer Zeidan, MBBS, MHS: Myelodysplastic syndromes are somewhat different from other cancers in the sense that many blood cancers usually have a lot of cells in the blood. For example, in acute myeloid leukemia, you would have a lot of those premature white cells in the blood. In multiple myeloma, you have a lot of those plasma cells. In lymphomas, you have a lot of those immature lymphoblasts or lymphocytes. What happens in myelodysplastic syndrome is that of those abnormal cells that are proliferating quickly are dying within the bone marrow before they get released into the blood, so we end up in a situation called paradoxical hypercellularity in the bone marrow. There are many cells within the bone marrow, but they are dying before they go to the blood, so they end up with pancytopenia: low blood counts while there are many cells in the bone marrow. There is another term that we use for phenomena: effective hematopoiesis. There is a lot of proliferation going on in the bone marrow, but because they are abnormally maturing and dysregulated, they die before they get released into the blood, leading to low blood counts.

Bart Scott, MD, MS: When talking about progression of MDS, it’s important to remember that most patients with MDS do not progress to AML. We tend to think that all patients with MDS get AML, but that’s not true. Particularly for patients who have lower-risk disease during their lifetime, they would not likely progress to AML. When you look at the risk of progression to AML, the model that we use is called the IPSS-R: International Prognostic Scoring System Revised. In that system, for patients who have high-risk disease, for instance, or what we call very poor-risk disease, 25% would progress to AML on average at about 0.7 year. If you look at good-risk patients, it would take about 9.4 years for about 25% of patients to progress to AML. For patients who have better-risk disease, during their lifetime, they would not likely progress to AML.

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