Budget impact of including ribociclib in combination with letrozole on US payer formulary: first-line treatment of post-menopausal women with HR+/HER2-advanced or metastatic breast cancer

Objectives: The combination of a cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitor with the aromatase inhibitor letrozole is a safe and effective alternative to letrozole monotherapy for first-line hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This study evaluates the budget impact of using the CDK 4/6 inhibitor ribociclib plus letrozole as a first-line treatment option for postmenopausal women with HR+/HER2- advanced breast cancer, from a United States (US) payer perspective. Methods: A cohort-based budget impact model was used to calculate the incremental cost of introducing ribociclib plus letrozole over three years for the target population. The analysis compared two scenarios: treatment options excluding or including ribociclib plus letrozole. Market shares were derived from market research and the assumption was the introduction of ribociclib plus letrozole would only displace existing CDK-based therapies. Treatment duration was based on the median time to treatment discontinuation or median progression-free survival for first-line treatment, and on clinical trial data for second- and third-line treatment. Acquisition costs were based on wholesale acquisition costs and considered co-payment. Costs for drug administration and monitoring, subsequent therapy, and relevant adverse events were included. Results: Of 1 million insured members, 263 were eligible for CDK 4/6 inhibitor treatment. Cumulative total savings with ribociclib plus letrozole were $3.01M over three years, corresponding to a cumulative incremental cost saving of $318.11 per member treated per month. Conclusions: In the US, ribociclib plus letrozole represents a cost-saving first-line treatment option for postmenopausal women with HR+/HER2- advanced breast cancer.