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

Biosimilars are supported by limited clinical data at the time of approval. Recently, Nivestim (TM), 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 (TM) with reference filgrastim and pegfilgrastim in FN prevention in patients receiving high-risk FN chemotherapy. 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). 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/mu L 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. No differences in biosimilar effectiveness were detected. The clinical relevance of the profound neutropenia found in the biosimilar cohort needs further attention.