Refractory anaemia with excess of blasts in transformation re-evaluated with the WHO criteria: identification of subgroups with different survival.

One of the major changes suggested by the World Health Organization (WHO) classification with respect to the French-American-British (FAB) proposal for myelodysplastic syndromes (MDS) was to lower the bone marrow (BM) blast count from 30 to 20%, thus eliminating the refractory anaemia with excess of blasts in transformation (RAEB-t) category. However, a general consensus has not been reached, and several authors still retain RAEB-t as an MDS sub-entity. We re-evaluated our series of 74 patients classified as RAEB-t according to the FAB criteria by stratifying them into two subsets: patients with at least 5% peripheral blast (PB) cells but with BM blasts <20% (group I) and patients with BM blastosis between 20 and 30% and PBs <5% (group II). We found differences among the two groups regarding sex, haematological parameters at presentation (white blood cell and neutrophil counts, haemoglobin level) and frequency of infectious episodes during the course of disease. We did not find differences as to the frequency of acute myeloid leukaemia transformation, but a significant difference was evidenced as to survival (9.3 vs. 16 months in group I vs. group II, respectively; p = 0.02). Furthermore, at our institution, we compared the RAEB-t group I patients who, based on >5% PBs, should be included in the RAEB-II category according to the WHO criteria, with a group of 98 patients who were diagnosed as RAEB-II according to the WHO criteria. The findings showed that the aggregation of these two subsets appeared inappropriate, because patients of the two groups showed different clinical features and rates of acute transformation. In conclusion, the RAEB-t entity according to the FAB criteria, although including heterogeneous clinical patient subsets, should more likely be considered as an advanced stage of MDS, rather than a true acute myeloid leukaemia.