1141 POSTER Evaluation of extended dosing intervals versus weekly dosing of darbepoetin alfa (DA): A phase 2 study in cancer patients (pts) with chemotherapy-induced anemia (CIA)

Abstract

In 2005, the mean weekly dose ratio of epoetin alfa (EA) to darbepoetin alfa (DA) in clinical practice was estimated to be ∼400 to 1. In 2006, a 500-μg dose and new dosing schedule was approved for DA in the United States. In 2007, the warnings and dosing/administration sections were modified for both agents. All of these factors may have changed the way that physicians use EA and DA. Previous studies of the use of erythropoiesis-stimulating agents (ESAs) in patients with anemia concomitant with chemotherapy may thus not reflect current clinical practice.The goal of this study was to examine the use and costs of ESAs in clinical practice in patients with anemia concomitant with chemotherapy.Using 2 large US health care claims databases, all adults (aged ≥18 years) were identified who received ESAs in 2008 and had evidence of receipt of chemotherapy ≤42 days before initial ESA receipt (ie, the index date). Episodes of care were defined as beginning on the index date and ending on the date of the last ESA claim that was followed by a ≥42-day gap without any receipt of ESAs, to which was added an assumed duration of clinical benefit (in days) based on the ESA and corresponding dose received. DA- and EA-treated patients were matched using propensity scoring. The mean weekly dose and cost of DA and EA during episodes of care was calculated using all information from relevant claims noted during such episodes. Each database was analyzed separately.In the first database, 475 patients with DA episodes of care were matched to an equal number of patients with EA episodes; in the second database, there were 424 matched pairs. In the first database, the mean (95% CI) weekly dose was 37,444 U (35,942 U–39,001 U) during EA episodes and 110 μg (108 μg–113 μg) during DA episodes; the mean weekly EA/DA dose ratio was 340 to 1. In the second database, the mean (95% CI) weekly dose was 37,047 U (35,944 U–38,175 U) during EA episodes and 121 μg (117 μg–125 μg) during DA episodes; the mean weekly EA/DA dose ratio was 306 to 1.The mean weekly EA/DA dose ratio during episodes of ESA care has declined in patients with anemia concomitant with chemotherapy, due at least in part to the availability and use of a new dose/dosing schedule for DA without similar changes for EA.