Background: A phase 2 trial was done to study effects of varying treatment schedule of Filgrastim (r-metHuG-CSF) on hematologic recovery following chemotherapy.
Patients and methods: Forty-six patients with extensive small-cell carcinoma of the lung were randomized to receive one of three Filgrastim schedules following cyclophosphamide, doxorubicin, and etoposide (CAE) chemotherapy for up to six cycles of treatment. Chemotherapy was delivered on days 1-3 of each 21-day cycle with Filgrastim initiated at 5 micrograms/kg/day subcutaneously (SC) beginning on day 4, day 6, or day 8 and continuing until post-nadir neutrophil recovery.
Results: During the first cycle of chemotherapy, the duration of neutropenia was similar for all three schedules; however, the pattern of absolute neutrophil count (ANC) recovery differed. In subsequent cycles of treatment, an improvement in the severity of neutropenia occurred in patients on the day-4 and day-6 schedules compared with the first cycle of chemotherapy. By contrast, patients on the day-8 schedule continued to experience neutropenia similar to that seen in cycle one. Patients on the day-8 schedule also experienced a greater magnitude of grade IV thrombocytopenia in later cycles of treatment.
Conclusion: Timing of Filgrastim administration post-chemotherapy has profound effects on hematologic recovery. Delay of Filgrastim until day 8 was associated with suboptimal hematologic recovery compared with administration of Filgrastim on day 4 or day 6. Initiation of Filgrastim on day 4 or day 6 showed a similar pattern of hematologic recovery. Beginning Filgrastim on day 6 is associated with a decrease in the total dose of Filgrastim administered.