OBJECTIVES : Trastuzumab is indicated for the treatment of adult HER2+ patients with early breast cancer (EBC), metastatic breast cancer (MBC) and metastatic gastric cancer (MGC). At the time of the analysis, there were three intravenous (IV) trastuzumab biosimilars available in Greece. The aim of this study was to assess the financial impact of IV trastuzumab biosimilars in HER2+ patients with EBC, MBC and MGC in the current trastuzumab market from payer perspective in Greece.

METHODS : A traditional budget-impact model with a 5-year time-horizon (2019-2023) was developed in Microsoft Excel. Epidemiological data were obtained from literature and were validated by a local clinical expert. The target population of the analysis consisted of incident (new) HER2+ patients eligible to receive biologics. The analysis included trastuzumab reference product and all relevant IV biosimilars. Market share predictions were based on internal market research. Following a payer perspective, only direct costs relating to drug acquisition were considered (€, 2018). Drug cost was obtained from the National Price Bulletin, applying the mandatory price discounts.

RESULTS : In the base case, total budget saving estimates ranged from €370,730 in 2019 to €613,091 in 2023, following the introduction of biosimilars. Among the total of 500 patients estimated to be on treatment, 85% (425 patients) was predicted to receive biosimilars, leading to cost-savings of €2,519,679 over 5 years-period (€48,655,712 vs €46,136,033). Total cost per patient decreased by €1,350 over the same time period. The model yielded average annual cost-savings of 5.18% (3.97% to 6.06%) compared to the current treatment scenario. When rebates and clawbacks were also accounted for, the relative budget impact resulted in cost savings of 9.01%.

CONCLUSIONS : The results of this economic assessment suggest that the introduction of trastuzumab IV biosimilars for the treatment of HER2+ patients with EBC, MBC and MGC could lead to considerable savings for the Greek public payer.