Darbepoetin alfa for treating chemotherapy-induced anemia in patients with a baseline hemoglobin level < 10 g/dL versus ≥ 10 g/dL: an exploratory analysis from a randomized, double-blind, active-controlled

Background: Several studies have shown that darbepoetin alfa, an erythropoiesis-stimulating agent (ESA), can reduce transfusions and increase hemoglobin (Hb) levels in patients with chemotherapy-induced anemia (CIA). Recent safety concerns, however, have prompted changes to ESA product information. In the European Union and United States, ESA therapy initiation for CIA is now recommended at a Hb level <= 10 g/dL. The present exploratory analysis examined how ESA initiation at this Hb level may impact patient care. Methods: Data from a phase 3 randomized trial were retrospectively reanalyzed. CIA patients with nonmyeloid malignancies were randomized 1: 1 to 500 mcg darbepoetin alfa every three weeks (Q3W) or 2.25 mcg/kg darbepoetin alfa weekly (QW) for 15 weeks. A previously published report from this trial showed Q3W dosing was non-inferior to QW dosing for reducing transfusions from week 5 to end-of-the-treatment period (EOTP). In the present analysis, outcomes were reanalyzed by baseline Hb < 10 g/dL and >= 10 g/dL. Endpoints included transfusion rates, Hb outcomes, and safety profiles. Results: This study reanalyzed 351 and 354 patients who initiated ESA therapy at a baseline Hb of < 10 g/dL or >= 10 g/dL, respectively. From week 5 to EOTP, the estimated Kaplan-Meier transfusion incidence (Q3W vs QW) was lower in the >= 10 g/dL baseline-Hb group (14% vs 21%) compared with the < 10 g/dL baseline-Hb group (36% vs 41%). By week 5, the >= 10 g/dL baseline-Hb group, but not the < 10 g/dL baseline-Hb group, achieved a mean Hb >= 11 g/dL. The Kaplan-Meier estimate of percentage of patients (Q3W vs QW) who achieved Hb >= 11 g/dL from week 1 to EOTP was 90% vs 85% in the >= 10 g/dL baseline-Hb group and 54% vs 57% in the < 10 g/dL baseline-Hb group. Both baseline-Hb groups maintained mean Hb levels < 12 g/dL and had similar safety profiles, though more patients in the >= 10 g/dL baseline-Hb group reached the threshold Hb of >= 13 g/dL. Conclusion: In this exploratory analysis, darbepoetin alfa Q3W and QW raised Hb levels and maintained mean Hb at < 12 g/dL in both baseline-Hb groups. The >= 10 g/dL baseline-Hb group had fewer transfusions and faster anemia correction. Additional studies should prospectively evaluate the relationship between Hb levels at ESA initiation and outcomes.