How did the Introduction of Biosimilar Filgrastim Influence the Prescribing Pattern of Granulocyte Colony-Stimulating Factors? Results from a Multicentre, Population-Based Study, from Five Italian Centres in the Years 2009-2014.

Background: Granulocyte colony-stimulating factors (G-CSFs) are biological products for which the main indication of use is chemotherapy-induced neutropenia. Biosimilars of G-CSFs have been available in Europe since 2007.

Objective: The objective of this study was to investigate the prescribing pattern of G-CSFs in five Italian centres using different healthcare policy interventions to promote the use of biosimilars in routine care.

Methods: This retrospective, population-based drug utilization study was conducted during the years 2009-2014 using the administrative databases of the Caserta, Treviso and Palermo Local Health Units (LHUs) and the Tuscany and Umbria regions. G-CSF users were characterized and the prevalence of use, proportion of biosimilar users and switching pattern of different G-CSFs were evaluated over time and across centres.

Results: Overall, 30,247 patients were treated with G-CSFs in the years 2009-2014, of which 29,083 (96.2 %) were naïve users. The overall prevalence of G-CSF use increased from 0.8 per 1000 inhabitants in 2009 to 1.1 per 1000 in 2014. An increase in the proportion of the use of the biosimilar filgrastim by the total G-CSF users was observed in all centres: from 0.2 % (2009) to 66.2 % (2014). However, heterogeneity across different centres was reported, with the largest increase in Treviso LHU (from 0 to 89.1 % from 2009 to 2014). During the first year of treatment, switching between different G-CSFs was frequent (20.3 %).

Conclusions: Heterogeneity in the use of G-CSF and, in particular, biosimilar filgrastim across different Italian centres was observed, probably due to different regional healthcare policy interventions. During the first year of treatment, switching between different G-CSFs was frequent. Considering the impact of biological drugs on pharmaceutical expenses, it is necessary to harmonize healthcare policies promoting the use of biological drugs with the lowest cost.