Open-label, randomized study of pegfilgrastim vs. daily filgrastim as an adjunct to chemotherapy in elderly patients with non-Hodgkin's lymphoma

Pegfilgrastim is composed of the protein filgrastim to which a 20-kDa polyethylene glycol (PEG) is covalently bound at the N-terminal residue resulting in decreased renal clearance and increased plasma half-life compared with filgrastim. This open-label, randomized, phase 2 study compared two doses of single administration pegfilgrastim (60 and 100 μg/kg) with daily doses of filgrastim (5 μg/kg/day) or no cytokine treatment after standard CHOP (cyclophosphamide, doxorubicin, vincristine and prednisolone) chemotherapy for non-Hodgkin's lymphoma in 50 elderly patients. The primary endpoint was the duration of grade 4 (severe) neutropenia (absolute neutrophil count <0.5 × 10⁹/l) in cycle 1. Duration of grade 4 neutropenia in cycle 1 was 2.2 (SD 1.2), 1.5 (SD 1.1), 0.8 (1.2) and 5.0 (2.0) days for patients who received pegfilgrastim 60 μg/kg, pegfilgrastim 100 μg/kg, filgrastim 5 μg/kg and no cytokine, respectively. The baseline characteristics of the pegfilgrastim and filgrastim groups were imbalanced with increased bone-marrow involvement and prior therapy in the former. When the treatment groups were balanced for these risk factors, duration of grade 4 neutropenia was comparable with 2.0 and 3.0 vs. 0.6 and 0.5 days for pegfilgrastim 100 μg/kg and filgrastim patients with and without these risk factors, respectively. The incidence of febrile neutropenia (defined as ANC < 0.5 × 10⁹/l and temperature > 38.2°C) was low (10% of patients). Pegfilgrastim was well tolerated with a safety profile similar to daily filgrastim. Once per chemotherapy cycle administration of pegfilgrastim was comparable to filgrastim in this clinical setting.