Background Given that biosimilar products are not generic products, a switch from filgrastim to a biosimilar filgrastim could be considered a change in treatment. Due to the nature and variability of manufacturing processes for biopharmaceuticals, biosimilar filgrastim has the potential to result in differences between safety and efficacy when compared with its reference product. Phase III studies have demonstrated their bioequivalence in terms of clinical efficacy and safety profile. Clinical efficacy was demonstrated by comparing the two products in three ways: duration of severe neutropenia, in which severe neutropenia was defined as absolute neutrophil count (ANC) < 0.5 x10⁹/l (DSN), time to ANC recovery (defined as ANC > 3 x10⁹/l) (TAR), mean number of injections (MNI). Other end points were also used.

Purpose To evaluate biosimilar filgrastim efficacy in the Hospital Fernando Fonseca clinical setting during its first six months of use.

Materials and methods This was an observational, transversal, non-randomised, retrospective study. Two assessment periods were created: October 2010 – March 2011 (filgrastim data) and April 2011-September 2011 (biosimilar filgrastim data). The authors called each unit of data entered, which was the act of dispensing the product, an episode. Within each period, The authors identified four types of dispensing settings: non-oncology inpatient dispensing (NOI); oncology inpatient dispensing (OI); prophylactic outpatient oncology dispensing (POO); treatment outpatient oncology dispensing (TOO). End points for each of these settings were: NOI and OI: DSN and TAR; POO – percentage of treatments and mean number of injections; TOO – percentage re-treatments and MNI.

Results Filgrastim data In NOI there were 8 valid episodes with mean DSN =1.8 days and mean TAR=4.4 days; in OI there were 4 episodes with mean DSN =3 days and mean TAR=6 days; in TOO there were 80 episodes with no re-treatments (0%) and MNI=2.6; in POO there were 113 episodes in which 3 were treatments (2.7 %) and MNI= 3.6. Biosimilar filgrastim data In NOI there were 23 valid episodes which translates as mean DSN =2 days and mean TAR=4.4 days; in OI there were 9 episodes with a mean DSN =3.5 days and mean TAR=5.8 days; in TOO there were 53 episodes with 1 re-treatment (1.9%) and MNI=2.5; in POO there were 108 episodes in which 5 were treatments (4.6%) and MNI=3.9.

Conclusions According to our results there were no significant differences in terms of clinical efficacy between the two filgrastims. Moreover, there were no reports of differences in the safety profile. Given the fact that there was a tremendous reduction in hospital expenditure with biosimilar filgrastim this alternative provides a highly cost-effective option.