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Classification and Risk Scoring in MDS

Chapter 11 - Myelodysplastic Syndromes in the Senior Patient

Based on morphologic features MDS are classified according to the FAB (French-American-British) or World Health Organization (WHO) proposal. These classifications are based on the morphological examination of dysplastic features in haematopoietic cells, the presence of ring sideroblasts and the percentage of bone marrow blasts. Presently, the WHO-classification is most widely used.

The WHO Classification of Myelodisplastic Syndromes 2008

  • Refractory cytopenias with unilineage dysplasia (RCUD)
    • Refractory anaemia (RA)
    • Refractory neutropenia (RN)
    • Refractory thrombocytopenia (RT)
  • Refractory anaemia with ring sideroblasts (RARS; ³15% BM ringed sideroblasts)
  • Refractory cytopenia with multilineage dysplasia (RCMD)
  • Myelodysplastic syndrome unclassified (MDS-U)
  • MDS associated with isolated del(5q)
  • Refractory anaemia with excess of blasts-1 (RAEB-1, 5–9% BM blasts)
  • Refractory anaemia with excess of blasts-2 (RAEB-2, 10–19% BM blasts)

As the overall survival and the rate of transformation into AML vary quite considerably among patients with MDS, even within morphological subgroups, much attention has focused on the identification of additional prognostic parameters. The International Prognostic Scoring System (IPSS) published in 1997 has become the most widely used risk assessment tool for MDS (Table 1).

The risk score IPSS (International prognostic scoring system)

A revised IPSS (IPSS-R) was developed in 2012 (Table 2).

The risk score IPSS-R (International prognostic scoring system - revised)

Improvements include a refined classification of cytogenetic abnormalities. More detailed cut-offs for bone marrow blast counts and cytopenias, weighted for their severity, are integrated. Age has been included resulting in the IPSS-RA (Table 3).

IPSS-R – survival related to age

The IPSS-R has been validated in several studies and represents the gold-standard for clinical risk assessment in patients with primary MDS. Based on the IPSS patients are divided into lower-risk (Low to intermediate-1 IPSS; very low, low to intermediate IPSS-R) and higher-risk (Intermediate-2 to high IPSS; high to very-high IPSS-R) MDS. These prognostic subgroups differ significantly in survival and rates of leukaemic transformation and maintain their prognostic significance even in MDS patients aged 70+. Both, IPSS and IPSS-R have improved risk stratification in clinical trials and are widely used for decision-making in clinical practise. However, IPSS and IPSS-R were established in primary MDS at initial diagnosis. Thus, limitations of both scores are the lack of data on dynamic aspects and therapy-related MDS. Moreover, molecular abnormalities, which are emerging as one of the most relevant clinical prognosticators, have not yet been integrated in IPSS/IPSS-R at all.

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