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MDS Staging: World Health Organization Typing System
A newer, slightly more complicated system for classifying MDS has been developed by the World Health Organization (WHO). Along with the cell type and maturity of the cells, this system takes into account other factors, such as chromosome changes in the cells and whether or not the leukemia is the result of previous cancer treatments. It classifies MDS according to factors that differ from those of the FAB system, including:
Considers molecular and chromosomal (cytogenetic) data
Defines RAEB-T to be a leukemia rather than a subtype of MDS
Defines patients with more than 20% blasts in marrow as having acute myeloid leukemia (AML)
Includes juvenile myelomonocytic leukemia (JMML) and chronic myelomonocytic leukemia (CMML) in the MDS/MPD category
According to the WHO typing system, MDS includes the following subtypes:
Refractory cytopenia with unilineage dysplasia (RCUD), which includes subtypes:
Refractory anemia (RA)
Refractory neutropenia (RN)
Refractory thrombocytopenia (RT)
Refractory cytopenia with multilineage dysplasia (RCMD): <5% blasts
Refractory anemia with ring sideroblasts (RARS): <5% blasts with RS
Refractory anemia with excess blasts type 1 (RAEB-1): 5-9% blasts
Refractory anemia with excess blasts type 2 (RAEB-2): 10-19% blasts
MDS with isolated deletion 5q (5q-syndrome): <5% blasts
Unclassifiable MDS (MDS-u)
MDS Staging: International Prognostic Scoring System (IPSS)
The International Prognostic Scoring System (IPSS) aids doctors in assessing the severity of a patient's MDS. The IPSS uses three "prognostic indicators" to predict the course of the patient's disease:
The percentage of blast cells in the marrow
The type of chromosomal changes, if any, in the marrow cells
The presence of one or more low blood cell counts (cytopenias)
Each indicator is rated according to its severity, and doctors come up with a "score" that describes the patient's risk. Risk categories are:
The low and intermediate categories are sometimes combined into a lower risk group; the intermediate-2 and high categories are sometimes combined into a higher risk group.
A treatment plan is designed around the patient's score and the doctor's personal observations of the patient.
MDS Staging: Revised International Prognostic Scoring System (IPSS-R)
Our program also uses the revised International Prognostic Scoring System (the IPSS-R) for Myelodysplastic Syndromes. This revised IPSS-R includes five rather than three cytogenetic prognostic subgroups with specific and new classifications of a number of less common cytogenetic subsets, splitting the low marrow blast percentage value, and depth of low blood counts (cytopenias). In addition to the major prognostic variables of marrow blasts, cytogenetics and peripheral low blood counts, cytopenias, additive features for survival include patient age, performance status, serum ferritin and LDH.
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