Comparison of effectiveness of biosimilar filgrastim (Nivestim™), reference Amgen filgrastim and pegfilgrastim in febrile neutropenia primary prevention in breast cancer patients treated with neo(adjuvant) TAC: a non-interventional cohort study.

PURPOSE: Biosimilars are supported by limited clinical data at the time of approval. Recently, Nivestim™, a biosimilar of reference of filgrastim, was approved for prevention of chemotherapy-related febrile neutropenia (FN). To add clinical experience to this new biosimilar, we performed a study to compare the effectiveness of Nivestim™ with reference filgrastim and pegfilgrastim in FN prevention in patients receiving high-risk FN chemotherapy.

METHODS: This is a comparative cohort study, with retrospective data collection. Three cohorts were identified according to the type of primary prophylaxis employed over different time periods: reference filgrastim (2004-2006), pegfilgrastim (2007-2008) and biosimilar filgrastim (2011-2012). The study included female patients with early breast cancer that received FN primary prophylaxis during (neo)adjuvant docetaxel/doxorubicin/cyclophosphamide (TAC).

RESULTS: Reference filgrastim cohort included 147 patients and pegfilgrastim and biosimilar filgrastim cohorts 139 and 134 patients, respectively. FN rates per patient/cycle were 16 % (95 % confidence interval (CI) 10.2-22.5 %)/3 % (95 % CI 2.1-4.7 %) in the reference filgrastim group, 9 % (95 % CI 4.5-14.6 %)/2 % (95 % CI 1.3-3.6 %) in the pegfilgrastim group and 16 % (95 % CI 10.0-22.9 %)/4 % (95 % CI 2.5-5.3 %) in the biosimilar filgrastim cohort. The median absolute neutrophil count (ANC) at FN presentation was lower in the biosimilar group in comparison with reference filgrastim. FN episodes with ANC < 100 cells/μL were more frequent in the biosimilar group (50 %) when compared with reference filgrastim (4 %) and pegfilgrastim (6 %). No differences concerning FN complications were seen, with the exception of more chemotherapy delays in the biosimilar group when compared with pegfilgrastim.

CONCLUSION: No differences in biosimilar effectiveness were detected. The clinical relevance of the profound neutropenia found in the biosimilar cohort needs further attention.