While both the biosimilar filgrastim and biosimilar pegfilgrastim were effective in reducing the incidence of neutropenia, adverse events related to granulocyte-colony stimulating factor therapy were significantly higher in patients who received pegfilgrastim.
In Iran, where biosimilar filgrastim and biosimilar pegfilgrastim are available to patients, both agents are used for the prophylaxis of neutropenia in patients with breast cancer who are undergoing myelosuppressive chemotherapy. The longer-acting nature of pegfilgrastim, and its single-dose administration, offers convenience over multiple doses of filgrastim, but the grade of neutropenia and adverse events (AEs) associated with the 2 available products, according to a recent study, have not yet been compared in a crossover pattern.
The study, conducted at 2 centers in Iran, compared 24 patients’ grade of neutropenia and AEs after receiving biosimilar filgrastim (Zarxio) and biosimilar pegfilgrastim (Pegagen, a product manufactured by CinnaGen and approved in Iran).
The patients, all of whom were being treated with dose-dense chemotherapy, were randomly assigned to 2 arms. The first arm received 6 mg of pegfilgrastim 24 hours after the first cycle of chemotherapy, followed by a daily subcutaneous dose of 300 μg of filgrastim for 6 days after the second cycle of chemotherapy. The second arm was treated with daily filgrastim after the first cycle of chemotherapy, then with pegfilgrastim after the second cycle.
One week after the first cycle of chemotherapy, the mean level of white blood cells (WBCs) was 5149 in the filgrastim group and 4556 in the pegfilgrastim group. Two weeks post chemotherapy, the mean WBC count for the 2 groups was 4422 and 9311, respectively, suggesting that pegfilgrastim was more protective against neutropenia than filgrastim was. However, the same parameters were measured after the second course of chemotherapy, and no significant difference was found; crossover analysis showed no significant difference in cell blood count parameters between the 2 groups.
The investigators also measured the total AEs reported with use of filgrastim and pegfilgrastim, and found significant differences in gastrointestinal side effects and bone pain. While 29.2% of patients receiving pegfilgrastim reported nausea and abdominal pain, no patients receiving filgrastim reported the same. With respect to bone pain, 20.8% of patients receiving pegfilgrastim reported this AE, while none of the patients receiving filgrastim did so.
The authors conclude that, while both the biosimilar filgrastim and biosimilar pegfilgrastim were effective in reducing the incidence of neutropenia, AEs related to granulocyte-colony stimulating factor therapy were significantly higher in patients who received pegfilgrastim.
Ashrafi F, Salmasi M. Comparison of the effects of pegylated granulocyte-colony stimulating factor and granulocyte-colony stimulating factor on cytopenia induced by dose-dense chemotherapy in breast cancer patients. J Res Med Sci. 2018;23:73. doi: 10.4103/jrms.JRMS_463_17.