BACKGROUND: Heil et al (Blood ‘97) demonstrated that the duration of neutropenia and its clinical consequences following induction chemotherapy for AML were significantly reduced by the addition of filgrastim, with no increased risk of death, second malignancy or relapse (ASH ‘99). A single injection of pegfilgrastim has been shown to be comparable to daily injections of filgrastim in the management of chemotherapy-induced neutropenia. The primary aim of this trial was to estimate the difference in time to recovery from severe neutropenia (SN, ANC < 0.5 x109/L) in the first induction chemotherapy cycle (Induction 1) in AML subjects treated with pegfilgrastim or filgrastim.

METHODS: Subjects with de novo AML received 1 or 2 courses of induction chemotherapy (idarubicin 12mg/m2 IV days 1–3, cytarabine 100mg/m2 IV 12 hourly days 1–7 [IA 3+7]) then, if in remission, consolidation chemotherapy (cytarabine 2 [subjects < 55 years] or 3g/m2 [subjects ≥ 55 years] IV 12 hourly days 1, 3, 5). Subjects received either single administration 6μg pegfilgrastim or daily 5μg/kg filgrastim starting 24 hours after completion of chemotherapy until neutrophil recovery. Time to recovery from SN was defined as the number of days from the first day of chemotherapy until the first of two ANC consecutive values after the nadir that were ≥ 0.5 x 109/L whereas duration of SN was defined as the total number of days during the cycle with an ANC < 0.5 x 109/L.

RESULTS: Of 84 subjects randomised into the study, 83 received study drug (42 pegfilgrastim, 41 filgrastim). The treatment groups were generally well balanced for demographics and baseline characteristics. The median time to recovery from SN (ANC < 0.5 x109/L) in Induction 1 was 22 days in both treatment groups (95% CI for treatment difference: −1.9, 1.9). There was also no statistically significant difference in the median duration of SN between the 2 groups (21 days pegfilgrastim, 20 days filgrastim). Subjects in the filgrastim group required a median of 16 daily injections compared to a single administration of pegfilgrastim in the second group. Median serum concentration of pegfilgrastim in Induction 1 remained above clinically relevant concentrations until 21 days after the start of chemotherapy, results that are consistent with the neutrophil-mediated clearance of pegfilgrastim. The incidence of serious adverse events was comparable between the 2 groups except for infectious complications, which were higher in the filgrastim group (5 subjects [12%] pegfilgrastim versus 9 subjects [22%] filgrastim).

CONCLUSION: In the setting of the first cycle of IA 3+7 induction chemotherapy in AML patients, once per cycle administration of 6 mg pegfilgrastim or daily administration of 5mg/kg filgrastim result in similar median time to recovery to ANC ≥ 0.5 x109/L. Pegfilgrastim is safe and well tolerated in this subject population.

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