The Cost-Effectiveness of CDK4/6 Inhibitors in Treating HR+/HER2- Metastatic Breast Cancer Patients in the USA: When Non-medication Expenses are Considered.

Background And Objective: Cyclin-dependent kinase (CDK)4/6 inhibitors in combination with endocrine therapy (ET) significantly enhance progression-free survival and overall survival in patients diagnosed with HR+/HER2- metastatic breast cancer (MBC). However, they are highly expensive, and their economic impact has not been fully evaluated. This is a retrospective secondary analysis evaluating the cost effectiveness of these drugs, differentiating between medication-related and non-medication costs from a healthcare perspective.

Methods: We identified 3879 patients diagnosed with MBC who received either CDK4/6i+ET (N = 2137) or ET alone (N = 1742) as first-line treatment between February 2015 and November 2021 using a USA-wide electronic health record-derived de-identified database. SEER-Medicare claims spending data were used to quantify monthly costs as a supplement to the database. Relevant costs included prescribed medications (ET and/or CDK4/6i) and overall other costs. The effectiveness was measured as progression-free duration in months. The incremental cost effectiveness ratio (ICER) analysis was conducted to examine the cost effectiveness of first-line CDK4/6i as compared with first-line ET alone.

Results: For medication costs, CDK4/6i+ET (mean cost: $240,723.7; mean effect: 19.2 months of delayed progression) compared with ET alone (mean cost: $5159.7; mean effect: 16 months without progression) resulted in an ICER of $73,098 per month of delayed progression. For non-medication costs, CDK4/6i+ET (mean cost: $43,656.6) compared with ET alone (mean cost: $66,083.5) resulted in an ICER of - $7178 per month of delayed progression.

Conclusion: The cost of treating HR+/HER2- MBC is driven by the cost of CDK4/6i. Using CDK4/6i+ET reduces non-medication costs compared to ET alone, but these savings are offset by high CDK4/6i medication costs. Lowering the market cost of CDK4/6i or targeting those who can benefit the most could improve the cost effectiveness of CDK4/6i from Medicare perspective.