This combined, retrospective analysis compared once-per-chemotherapy-cycle pegfilgrastim with daily Filgrastim in breast cancer patients undergoing myelosuppressive chemotherapy enrolled in two similarly designed, randomized, double-blind, pivotal trials. On day 2 of each chemotherapy cycle, a single subcutaneous (SC) injection of pegfilgrastim [either 6 mg (n=77) or 100 µg/kg (n=149)] was administered, or daily Filgrastim SC injections (5 µg/kg/day; n=222) were initiated and continued until either absolute neutrophil count (ANC) ≥10x109/l after the expected nadir or for up to 14 days, whichever occurred first. Individually, each of these trials demonstrated that a single pegfilgrastim injection per cycle is as effective at reducing the duration of severe neutropenia as daily injections of Filgrastim. Clinical efficacy data from the two trials were combined for analysis (n=448). The risk of febrile neutropenia (FN; absolute neutrophil count <0.5x109/l with fever ≥38.2°C) was significantly lower [11% vs 19%, respectively; relative risk = 0.56 (95% confidence interval: 0.35, 0.89)] in patients receiving pegfilgrastim than for those receiving Filgrastim. Trends towards lower risks of hospitalization and intravenous anti-infective use were also observed. These observations were consistent irrespective of risk factors, including age, disease stage, performance status and prior treatment. Pegfilgrastim may offer patients more effective protection against neutropenic complications of chemotherapy with fewer injections and less disruption to their lives.

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