Transfusion risk in cancer patients with chemotherapy-induced anemia when initiating darbepoetin alfa therapy at a baseline hemoglobin level of <9 g/dL versus 9 to <10 g/dL versus >= 10 g/dL: an exploratory analysis of a phase 3 trial
Darbepoetin alfa (DA) is an erythropoiesis-stimulating agent (ESA) approved for treating chemotherapy-induced anemia (CIA). Safety concerns have prompted changes to the ESA-product information, which now recommends initiating ESAs at hemoglobin (Hb) levels < 10 g/dL (US) or <= 10 g/dL (EU). The present exploratory analysis of a DA trial examined how baseline-Hb levels at ESA initiation affect transfusion rates, Hb response, and safety outcomes in CIA patients. Data were retrospectively analyzed from a phase 3 trial of CIA patients randomised to 500 mcg DA every 3 weeks (Q3 W) or to 2.25 mcg/kg DA weekly (QW) for 15 weeks. In the current analysis, data were reanalyzed by baseline-Hb categories of <9 g/dL (n = 126), 9 to <10 g/dL (n = 225), and >= 10 g/dL (n = 354). The Q3 W and QW groups were combined. Transfusion rates were highest in the <9 g/dL baseline-Hb group in all time periods examined. The Kaplan-Meier percentage (95% CI) of patients achieving Hb >= 10 g/dL was 68% (59, 78) and
88% (82, 92) in the <9 g/dL and 9 to <10 g/dL baseline-Hb groups, respectively. With lower baseline-Hb, incidence of a >= 1 g/dL-Hb rise in 14 days progressively decreased. Incidence of venous thromboembolic events was similar in all baseline-Hb groups and similar between patients with or without a >= 1 g/dL-Hb rise in 14 days. Overall, transfusion risk increased and Hb response decreased at lower baseline-Hb levels in this exploratory analysis. When following ESA-product information to initiate ESAs at Hb <= 10 g/dL, the greatest benefit may be achieved when initiating close to 10 g/dL. Prospective studies are needed to further examine this hypothesis.