Prognostic Relevance of Retrospective WHO Re-Classification in 650 MDS Patients Diagnosed by FAB Criteria

We retrospectively re-classified according to WHO criteria our series of consecutive 650 MDS cases, in order to validate the prognostic role of this classification in a unicentric series of patients. Based on FAB criteria, 196 patients had been diagnosed as RA, 41 as RARS, 242 as RAEB, 74 as RAEB-t and 83 as CMML. The new WHO classification could be applied to 479 of the 650 patients; of 196 FAB-RA only 76 were classified as “pure” RA, with only anemia and erythroid dysplasia, whereas 87 patients were re-evaluated as RCMD, for the presence of peripheral cytopenias and dysplasia in ≥ 10% of 2 cell lines. Twenty-nine patients had cytopenias but with only unilineage dysplasia in granulocytes or megakaryocytes, and were re-interpreted as MDS, unclassified (MDS-U). Of 41 FAB-RARS, 32 maintained their diagnosis, whereas 9 patients were classified as RCMD-RS, based on criteria listed above. One-hundred-one patients were identified as RAEB-1, for the presence of 5–9% blasts in bone marrow, and < 5% peripheral blasts, whereas 141 patients were classified as RAEB-2 for the evidence of 10–19% and of 5–19% blasts in bone marrow and peripheral blood respectively. We tested the WHO classification in univariate analysis with respect to several clinical features at presentation. Significant correlations were found as to hemorrhagic symptoms in RCMD and RAEB-2 patients (p=0.014), acute transformation, with higher frequency in RCMD and RAEB-2 categories (p=0.002), transfusion dependence, with higher requirement in RAEB-2 (107/141 RAEB-2 vs 59/101 RAEB-1) and in RCMD (63/87 patients) categories; also the application of different scoring prognostic systems, such as the Bournemouth and Spanish, appeared to possess stastical significance (p=0.001 and p=0.002, respectively). No differences were found as to sex, age, infection occurrence and cytogenetic abnormalities among various subgroups. Kaplan-Meier survival test showed high significance, with median overall survival ranging from 55.8 months for pure RA to 22.6 months for RAEB-2 category (p=0.00001). In conclusion, the retrospective application of WHO classification to our series of MDS patients clearly identified prognostic correlations in various disease subtypes. Categorization of MDS entities according to WHO criteria may distinguish parameters of prognostic importance in large groups of patients with morphological similar features.