Unexpected Response to Erythropoietin Therapy in Intermediate-Low IPSS Myelodysplastic Syndromes.

INTRODUCTION: The myelodysplastic syndromes (MDS) are clonal hematopoietic disorders characterized by dysplasia and cytopenias, especially anemia. There is no widely accepted standard therapy for MDS. Exogenous erythropoietin (EPO) seems to be able to raise Hb levels and/or decrease transfusion requirements in patients with MDS, with reported responses rates of 25–30%. In our center, EPO has been used since 1999, based on the published recommendations, assessing the therapeutic response after 12 weeks of therapy.

OBJECTIVE: To analyze retrospectively the therapeutic response to EPO in 45 patients with MDS and anemia.

PATIENTS AND METHODS: 45 consecutive patients with MDS and calculable IPSS score, showing low or intermediate-1 risk, were treated with EPO from 1999 to 2006. From the initial 45 patients, 5 were excluded from the analysis because of lack of follow-up. The 40 selected patients belonged to the following FAB subgroups: AR 20 (50%), ARS 12 (30%), AREB 3 (7%) and LMMC 5 (12%). Other criteria for treatment were Hb levels <10 g/dL or transfusion requirements ≥ 2U/month and/or serum EPO levels <500 U/L. Different commercially available EPO were used: 31 (77%) of the patients received EPO-alfa/beta (30,000 U/week sc) and 9 (23%) darbepoetin (150μg/week sc). Erythroid response criteria followed those of the International Working Group: complete response (CR) with a >2 g/dL Hb increase or transfusion independence, and partial response (PR) with a 1–2 g/dL Hb increase or 50% decrease in transfusion requirements. Sixteen patients with no response after 12 weeks of therapy, continued with double EPO dose for a median of 10 weeks.

RESULTS: From the 40 patients selected, 22 (55%) were female with a median age of 76 years old (47– 86). Mean baseline Hb level was 8,4 g/dl (5,8–11). Serum EPO levels were measured in 33 patients: 23 (70%) presented <200 U/L and 10 (30%) between 200 and 500 U/L. Unexpectedly, as much as 19 (47,5%) of the 40 patients responded to treatment. 16 patients (40%) responded after twelve weeks: 7 of them (44%) showed CR and 9 (56%) PR. From the 24 patients who did not respond initially, 16 continued with double EPO dose and 3 (18%) of them responded after 8 weeks. Response rates in different FAB subgroups are shown in table 1. Median duration of all responses was 9 months (1–42 months), 12 months for CR and 5,5 months for PR. Interestingly, none of the subgroup with pretreatment EPO levels ≥200 responded (p=0,006). After an overall follow-up of 81 months, 7 selected patients died (3 due to blastic transformation and 4 due to causes not related to the disease).

CONCLUSIONS: The response to EPO therapy of MDS-related anemia in our center was unexpectedly high (47,5%). Patients who do not show response after 12 weeks of initial therapy, seem to improve from switching to higher EPO doses since 18% of patients treated with this scheme responded. In our study, ARS subgroup showed an unexpected high rate of response (66%), although they were treated without association of granulocyte-stimulating colony factor. Remarkably, pretreatment serum EPO levels <200U/L seems to be a valuable predictor of response since none of the patients with levels ≥200 U/L and <500 U/L responded in our study.