OBJECTIVES: Abemaciclib is the first and only approved CDK 4&6 inhibitor for the treatment of HR+, HER2- node-positive EBC at high risk of disease recurrence. The objective of this research was to evaluate the cost-effectiveness of abemaciclib plus adjuvant ET versus ET alone from a Spanish healthcare system perspective.

METHODS: A cohort state-transition model was developed with five health states: invasive disease-free survival (IDFS); non-metastatic recurrence; remission; metastatic recurrence; and death. Individual patient-level data (IPD) from the monarchE trial (NCT03155997) were used to parametrize IDFS, time to treatment discontinuation, and overall survival (without distant recurrence). In the absence of longer-term follow-up from monarchE, the non-metastatic and metastatic recurrence health states were informed by data from advanced breast cancer populations, inclusive of patients at high risk of disease recurrence, published sources, and clinical expert opinion. Maximum time on abemaciclib was 2 years with a minimum planned duration of 5 years for adjuvant ET. Resource use and costs were obtained from published sources. Costs were sourced for Year 2021 or latest available data. Health state utilities were derived from EuroQoL 5-dimension 5-level monarchE IPD and other sources. Costs and outcomes were calculated over lifetime and discounted at 3%.

RESULTS: The estimated total discounted costs (€107,886 vs. €73,818; difference: €34,068) and quality-adjusted life-years (QALYs; 12.45 vs. 11.30; difference: 1.15) were higher for abemaciclib plus ET compared with ET alone. The incremental cost-effectiveness ratio was €29,697 per QALY gained. The likelihood of abemaciclib plus ET being cost-effective versus ET alone was 90% under an assumed willingness-to-pay threshold of €35,000 per QALY gained.

CONCLUSIONS: Abemaciclib plus ET is a cost-effective treatment option versus ET alone for persons with HR+, HER2- node-positive EBC at high risk of disease recurrence in Spain.