Abstract
Background: Many medications administered to Medicare patients with hematological conditions are Part B drugs, including monoclonal antibodies, chemotherapeutic agents, and hematopoietic growth factors. The price of Part B drugs can have a profound impact on patient access to medications and outcomes. Medicare patients may choose to receive their coverage from either traditional Medicare or Medicare Advantage. While traditional Medicare pays for most Part B drugs using a transparent formula (average sales price plus 6%), Medicare Advantage payment rates are privately negotiated and not publicly available. In addition to patient affordability, Part B drug payment is a critical component of hematology practice economics. This study provides the first comparative analysis of payment differences between traditional Medicare and Medicare Advantage for Part B drugs, offering insights into how these models may differentially impact patient access to essential hematologic therapies and physician payment.
Methods: This retrospective study used a novel claims dataset from Kythera Labs, a large healthcare data clearinghouse that processes administrative claims from across the United States. This dataset includes billions of claims from Medicare, Medicaid, and commercial insurers, representing approximately 70–95% of all U.S. medical events since 2016. Kythera does not contain information on patients who are uninsured or who paid cash without the use of insurance. We identified the most expensive hematology Part B drugs by total cost using publicly available data from the Centers for Medicare and Medicaid Services' “Medicare Part B Spending by Drug” database. For these drugs, we then used the claims data from Kythera to identify all outpatient claims from 2022-2024 in both traditional Medicare and Medicare Advantage. For each claim, we identified the payer type (traditional Medicare or Medicare Advantage) and the amount paid by the insurer. Drugs with fewer than 1000 payments from either payer were excluded. To estimate and compare the average per drug unit difference in payments between traditional Medicare and Medicare Advantage, a Tweedie generalized linear model was used. This model was chosen for its ability to handle healthcare cost data, which often contains a large proportion of zero-dollar payments (which are important for including valid claims where the insurer paid nothing, such as when a patient had not yet met their deductible) alongside a right-skewed distribution of positive payments, in a single analysis.
Results: Across 317,075 claims for the top 15 highest-cost hematology Part B drugs, Medicare Advantage plans paid more per unit than traditional Medicare for all 15 drugs (p < 0.001). On average, Medicare Advantage plans paid 23.7% more per unit (95% confidence interval [CI], 21.6% to 25.8%; p < 0.001). The largest relative payment differences were observed for rituximab-pvvr (34.4% higher in Medicare Advantage; 95% CI, 26.5% to 42.4%; p < 0.001), elotuzumab (31.4% higher in Medicare Advantage; 95% CI, 0.1% to 62.8%; p < 0.001), and rituximab-abbs (31.4% higher in Medicare Advantage; 95% CI, 20.6% to 42.2%; p < 0.001). Payment differences were the most similar between traditional Medicare and Medicare Advantage for rituximab (3.1% higher in Medicare Advantage; 95% CI, -2.4% to 8.7%; p < 0.001) and daratumumab (8.2% higher in Medicare Advantage; 95% CI, 0.6% to 15.8%; p < 0.001).
Conclusions: While payments in traditional Medicare are well established, negotiated payments in Medicare Advantage are unknown and have implications for patient affordability and physician payment. We find that each drug in our sample is paid at a higher rate in Medicare Advantage than traditional Medicare, suggesting that Medicare Advantage beneficiaries may be responsible for greater cost-sharing than traditional Medicare beneficiaries for the same service, as most insurers set patient liability based on the drug's price. While this foundational analysis compares Part B drug payments between traditional Medicare and Medicare Advantage, future work should examine the amount paid by patients and payment differences between Medicare Advantage plans.
