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Erythroid response (ER) rates in myelodysplastic syndromes (MDS) patients treated with epoetin alfa (EPO): A meta-analysis using the International Working Group criteria (IWGc) for MDS response.

6572 Background: Refractory anemia is a clinical hallmark of MDS. The most consistently used therapy for this anemia is EPO. Prior to the introduction of IWGc in 1997, ER rates varied substantially between studies. The present meta-analysis was undertaken to compare ER rates in studies of EPO-treated patients in MDS when defined by either IWGc or non-IWGc.


METHODS
A systematic review and data extraction of studies published from 1990-2005 in MDS patients treated with EPO was performed and yielded 21 studies evaluating a total of 895 patients. Pooled estimates of ER rates, stratified by IWGc, were calculated using random-effects meta-analysis methods, which incorporated both between- and within-study variations. Univariate meta-regression analyses were conducted to identify study characteristics that were significant determinants of ER rate.


RESULTS
Ten studies (604 patients) used the IWGc to define ER (overall, major, minor), while 11 studies (291 patients) used other definitions. Mean age for all patients was 70.6 years; 45% women. Mean baseline (BL) serum erythropoietin level and proportion of patients with refractory anemia or refractory anemia with ringed sideroblasts were comparable between studies; however, the proportion of transfusion-dependent patients at BL was lower in the IWG studies vs the non-IWG studies (36% vs. 84%, respectively, p<.001). The pooled estimate of ER rate was significantly higher for the IWG studies compared to the non-IWG studies (50.5%, 95% CI: 38.6%-62.3% vs. 27.8%, 95% CI: 22.7%-32.8% respectively, p=.002). Among patients in the IWG studies who achieved an ER, 62% (188/305) achieved a major ER. Studies reporting mean BL serum erythropoietin level <400mU/mL, <65% of patients transfusion-dependent at BL and use of subcutaneous EPO were found to be associated with higher ER rates.


CONCLUSIONS
This meta-analysis of MDS patients treated with EPO demonstrates significantly higher ER rates in studies utilizing IWGc. These findings may be due to more refined definitions of ER and MDS diagnostic criteria as well as improvement in the management of anemia. [Table: see text].