Contemporary Patterns of Medicare Part B Spending on Immune Checkpoint Inhibitors (2018-2022)

PURPOSE Immune checkpoint inhibitors (ICIs) have transformed cancer care but impose a growing financial burden on Medicare. We characterized Medicare Part B spending and utilization patterns for ICIs from 2018 to 2022 to quantify expenditure trends and identify key cost drivers. METHODS We conducted a retrospective analysis of the Centers for Medicare & Medicaid Services (CMS) Medicare Part B Spending by Drug public summary files (aggregated Healthcare Common Procedure Coding System [HCPCS] drug-year data) from 2018 through 2022. For eight ICIs, we extracted total gross program spending, total dosage units (HCPCS billing units), and unique beneficiaries and calculated average spending per dosage unit, average spending per beneficiary, and growth metrics over time. RESULTS In 2022, total Medicare Part B spending across the eight ICIs was approximately $8.49 billion US dollars (USD). Pembrolizumab accounted for the largest spending ($4.94 billion USD) and beneficiary utilization (67,022 beneficiaries), followed by nivolumab ($1.85 billion USD; 26,957 beneficiaries). Average spending per beneficiary in 2022 (the primary cost metric, capturing dose frequency and treatment duration) ranged from $53,508 USD (durvalumab) to $80,705 USD (atezolizumab). Average spending per dosage unit varied widely as a secondary pricing measure, from $27.02 USD (cemiplimab) to $216.09 USD (dostarlimab). CONCLUSION Medicare Part B spending on ICIs is highly concentrated among pembrolizumab and nivolumab, and is driven primarily by beneficiary volume, with substantial heterogeneity in per-beneficiary spending across agents. As indications and utilization continue to expand, these therapies' fiscal impact warrants ongoing evaluation to inform Medicare payment policy and value-based oncology care.