Adoption of Bevacizumab Biosimilars in Medicare Part B: Socioeconomic and Geographic Variation, 2019-2023.

Abstract

Oncology biosimilars have been promoted to reduce Medicare Part B drug spending, yet adoption may vary across socioeconomic and geographic contexts. We quantified national trends in bevacizumab biosimilar adoption from 2019 through 2023 and examined variation by neighborhood deprivation and rurality. We conducted a repeated cross-sectional analysis using Medicare Part B Provider and Service Public Use Files from 2019 through 2023. Provider-drug-year observations were linked to zip-code‑level Area Deprivation Index (ADI) quintiles and Rural-Urban Commuting Area classifications. Outcomes included biosimilar market share over time, variation by ADI and rurality, mean Medicare allowed amount per administration, and estimated per-administration savings. The analytic sample included 11,803 provider-drug-year observations, 93.0% located in urban zip codes. Biosimilar adoption increased from 0.5% in 2019 to 31.9% in 2020, exceeded 50% by 2021 (57.5%), and remained more than 60% through 2023 (61.3%). In 2023, uptake ranged from 58.1% in the least deprived quintile (ADI Q1) to 81.3% in the most deprived quintile (ADI Q5) and was lower in nonurban than urban areas (33.6% <i>v</i> 62.0%). Mean allowed amounts for biosimilars declined from $69.70 in US dollars (USD) in 2019 to $33.36 USD in 2023, while originator amounts remained stable. Per-administration savings reached $36.40 USD (52.2%) by 2023 and were similar across ADI quintiles. From 2019 to 2023, bevacizumab biosimilars diffused rapidly in Medicare Part B, generating an estimated $84.5 million USD in aggregate savings, with per-administration savings exceeding 50% by 2023. However, adoption remained heterogenous across socioeconomic and rural-urban contexts, suggesting that variation in realized savings is driven primarily by differential diffusion rather than systematic pricing differences. Closing these gaps will likely require coordinated interventions addressing delivery, reimbursement, and clinician-level barriers to biosimilar adoption.