FAB and WHO classifications
The FAB classification has a long history of use to evaluate survival and risk for AML transformation (Table 1). The WHO classification has similar prognostic implications, based primarily upon the prognostic impact of blast percentage and the number of dysplastic lineages.
Patients with complex karyotypes and abnormalities in chromosome 7 have a poor prognosis, whereas those with a normal karyotype, −Y, 5q−, or 20q− have a favorable prognosis.
Peripheral cytopenias (hemoglobin level < 10 g/dL, absolute neutrophil count [ANC] < 1.8 × 109/L, and platelet count < 100 × 109/L) have a cumulative adverse effect on prognosis.
Other prognostic factors
Other parameters associated with a poor outcome include CD34 cell expression, high serum LDH, abnormal localized immature myeloid precursors, RAS mutations, severe thrombocytopenia, CDKN2B inactivation, TP53 mutations, and extent of genomic methylation. However, it is unclear whether these factors have independent prognostic value.
International Prognostic Scoring System (IPSS)
An International MDS Risk Analysis Workshop has proposed a system that combines clinical, morphologic, and cytogenetic data to generate a consensus prognostic system.
By multivariate analysis, the most significant independent variables were percentage of bone marrow blasts, cytogenetics, and number of cytopenias (Table 3). It is important to keep in mind, however, that other variables (eg, age and prior therapy) not included in this system may alter the prognosis and influence the results of therapy among patients in similar IPSS groups. Still, this may be the most valuable risk classification for treatment planning.
Other scoring systems
The IPSS and WHO classifications have the following limitations in assessing the risk of patients with MDS: excess weight toward percentage of blasts, lack of discrimination of patients with lower-risk disease, and other clinical characteristics.
Recently, several newer models have been developed to address these issues, such as the WHO classification-based prognostic scoring system and the M. D. Anderson low-risk model.
In one study, investigators found it possible to use the M. D. Anderson low-risk model to identify patients with lower-risk MDS and a poor prognosis who may benefit from early intervention (Tables 4 and 5). The implementation of this model may have significant implications for clinical trial design and eventually treatment decisions for patients with lower-risk MDS.