BACKGROUND: Biosimilars to originator bevacizumab (Avastin), such as bevacizumab-bvzr (Zirabev), can deliver substantial savings and/or expanded access to biologic therapy for patients with metastatic colorectal (mCRC) and non-squamous non-small cell lung cancer (mNSCLC). The objective of this study is to explore the cost-efficiency and budget-neutral expanded access of bevacizumab-bvzr in mCRC and mNSCLC in Medicare. METHODS: We developed a Medicare payer perspective simulation model of patients treated for mCRC and mNSCLC to estimate cost-savings from converting bevacizumab (originator) to bevacizumab-bvzr or alternative biosimilars such as bevacizumab-awwb, -maly, and -abcd. The target patient population receiving annual first-line systemic therapy was calculated using Medicare enrollment data, SEER cancer incidence rates in patients age ≥65, and an assumption that 39.3% and 77.2% of new diagnoses receive systemic therapy for mCRC and mNSCLC respectively based on recent evidence. 76.0% of systemically treated mCRC patients and 11.4% of incident mNSCLC patients were expected to be treated with bevacizumab-based regimens based on recent evidence. Costs were derived from the 2024 Average Sales Price (ASP). Results include per-patient per-month (PPPM) cost savings (vs. originator), total monthly savings in the cohort, and number needed to convert (NNC) to biosimilar to fund the treatment of an additional 100 patients. RESULTS: PPPM savings from conversion to bevacizumab-bvzr were ,205 in mCRC and ,410 in mNSCLC. In 100% conversion scenarios, full cohort monthly savings were 7,664,432 in mCRC ( CONCLUSION: In the first cost-efficiency and expanded access study of biosimilar bevacizumab in mCRC and mNSCLC, we find that bevacizumab-bvzr-based regimens can result in substantial cost savings relative to originator-based first line treatment in Medicare. These cost savings could be reinvested to treat a substantial number of additional patients with mCRC or mNSCLC, or fund other costs of care in Medicare, on a budget-neutral basis.