Background: G-CSFs are utilized to lower the incidence of febrile neutropenia (FN) in patients with cancers treated with chemotherapy. In 2015 filgrastim-sndz was the first biosimilar to be approved and launched in the US. Limited data exists on the impact of biosimilars on patient out-of-pocket (OOP) expenditures. The objective of this simulation model is to estimate potential OOP cost savings through use of filgrastim-sndz (FIL-S) over reference filgrastim (FIL-REF) from a Medicare lung cancer patient perspective. Methods: An Excel simulation analysis was conducted among lung cancer patients treated with biosimilar FIL-S or FIL-REF (identified through HCPCS codes). Data from the 2016 Medicare Limited Data Set was used to populate the model. Average Medicare payment to the provider and beneficiary OOP responsibility per claim of either FIL-S or FIL-REF were calculated. The average OOP reduction per claim for a FIL-S beneficiary relative to a FIL-REF beneficiary was multiplied to a hypothetical FN prevalent population of 100,000 beneficiaries (average of 10 claims per beneficiary) to estimate the potential OOP savings. Results: Data from 525 FIL-S and 621 FIL-REF claims were analyzed. The average Medicare allowed charge amount per claim for a FIL-S beneficiary was $381.7 versus $419.1 for a FIL-REF beneficiary, while corresponding average Medicare payments to the provider were $299.3 and $327.4, respectively. On an average, OOP responsibility for a FIL-S beneficiary was lower compared to a FIL-REF beneficiary ($76.4 vs. $85.0) leading to a cost saving per claim of approximately $8.60. When extrapolated to 100,000 beneficiaries (1,000,000 claims), the overall cost saving was projected to be around $8.6 million. Conclusions: Our simulation model estimated potential OOP Medicare lung cancer beneficiary savings of around $8.6 million, based on a hypothetical population of 100,000 FN beneficiaries, with the use of biosimilar FIL-S over FIL-REF. Further real-world analyses are required to evaluate the true cost savings potential with the use of biosimilars over reference biologics.