Usefulness and prognostic impact on survival of WHO reclassification in FAB low risk myelodyplastic syndromes

In 1999, WHO proposed a revised classification for myelodysplastic syndromes (MDS). According to this system, FAB low risk MDS (RA and RARS) were defined as such when the presence of dysplastic features was only restricted to the erythroid lineage, and new categories, refractory cytopenia with multilineage dysplasia (RCMD) and refractory cytopenia with multilineage dysplasia and ringed sideroblasts (RCMD-RS), were added. In a retrospective analysis of 240 consecutive patients diagnosed at our institution as having FAB RA and RARS, we reclassified the disease following the WHO criteria and we found that 179/214 patients (84%) still remained in the RA category, while 35/214 (16%) moved to RCMD. Moreover, 17/26 patients (65%) maintained the RARS diagnosis, whereas 9/26 (35%) were re-classified as RCMD-RS. We detected differences among the WHO subgroups as to age and sex distribution as well as to median survival observed by stratifying patients according to different prognostic scoring systems. Furthermore we confirmed the usefulness of WHO segregation with regard to its predictive value for evolution into acute leukaemia. Our study provides evidence that WHO classification may have prognostic impact on MDS subgroups which are usually categorized by FAB as having a favourable outcome.