A retrospective cohort study to assess the impact of therapeutic substitution of darbepoetin alfa for epoetin alfa in anemic patients with myelodysplastic syndrome.

Darbepoetin alfa and epoetin alfa are used to treat anemia in the undertreated population of patients with myelodysplastic syndrome (MDS). We implemented guidelines to switch anemic patients with MDS from epoetin alfa 40,000 U weekly to darbepoetin alfa 200 microg every 2 weeks and then conducted a retrospective cohort study of the initial 263 treated patients. Patients (> or = 18 years old, MDS diagnosis) were either previously treated with epoetin alfa (received 16 weeks of prior epoetin alfa and either switched to darbepoetin alfa or remained on epoetin alfa) or treatment-naive (no previous erythropoietin therapy and received only 1 agent for 16 weeks). Both major response and minor response based on the International Working Group criteria were calculated. The study was not powered to statistically compare treatment groups; values presented are for descriptive purposes only. Data from 244 patient records were included: 142 previous epoetin alfa patients (80 switched to darbepoetin alfa, 62 remained on epoetin alfa) and 102 naive patients (56 darbepoetin alfa, 46 epoetin alfa). Major response rates were similar between treatment groups in both the naive (46% for darbepoetin alfa, 35% for epoetin alfa) and previous epoetin alfa groups (26% for darbepoetin alfa, 17% for epoetin alfa). Overall response rates were 42%-76% across treatment groups. No differences in transfusions across groups were observed. Treatment of anemic patients with MDS with either darbepoetin alfa or epoetin alfa appeared to be effective. Whereas epoetin alfa was most frequently administered on a weekly basis, darbepoetin alfa was most frequently administered every 2 weeks, which may offer the benefit of convenience with its less frequent dosing.