Cost-effectiveness of ribociclib plus endocrine therapy in HR-positive, HER2-negative early breast cancer in the United States.

11049 Background: Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are an efficacious treatment for HR-positive (HR+), HER2-negative (HER2-) early breast cancer. The phase 3 NATALEE trial demonstrated that ribociclib ($12,000 monthly) plus a nonsteroidal aromatase inhibitor (endocrine therapy) significantly improved invasive disease-free survival. We performed the first cost-effectiveness analysis of ribociclib plus endocrine therapy in patients with HR+, HER2- early breast cancer in the United States (US). Methods: We constructed a partitioned survival model based upon clinical data from the NATALEE trial, employing a health system perspective across all accepted willingness-to-pay (WTP) thresholds in the US. Patients with a median age of 51 years entered the model to receive (1) ribociclib plus endocrine therapy versus (2) endocrine therapy alone. Standard extrapolation techniques were utilized to extend overall and invasive disease-free survival curves to a 10-year time horizon. Costs were informed by the US Centers for Medicare & Medicaid Services. Effectiveness was informed by age-, sex-, and breast cancer-specific utility values and was measured in both quality-adjusted life years (QALYs) and equal value life years (evLYs). The primary outcome was the incremental cost-effectiveness ratio (ICER) in USD per evLY. We concluded with deterministic sensitivity analyses and threshold and probabilistic analyses, with all input parameters informed by relevant probability distributions. Results: In the base-case, ribociclib plus endocrine therapy and endocrine therapy alone accrued discounted costs of $442,000 and $186,000, with discounted QALYs/evLYs of 7.76/7.79 and 7.57/7.57, respectively. This resulted in an ICER of $1.2 million/evLY (and $1.3 million/QALY) for the addition of ribociclib (Table 1). Deterministic sensitivity analysis revealed our model was only sensitive to the price of ribociclib: no other parameter changed the conclusion. Threshold analysis demonstrated that a 90% reduction in the price of ribociclib would be necessary for ribociclib plus endocrine therapy to be cost-effective even at the highest WTP threshold. Endocrine therapy alone was favored in 100% of 10,000 Monte Carlo simulations across the entire range of accepted WTP thresholds in the US. Conclusions: At current pricing, ribociclib with endocrine therapy is not expected to be a cost-effective strategy compared to endocrine therapy alone for patients with HR+, HER2- early breast cancer in the US. These results align with prior studies in other countries assessing the cost-effectiveness of CDK4/6 inhibitors in HR+, HER2- early breast cancer. Base-case analysis results. Strategy Cost (USD) QALY evLY ICER (USD/evLY) [95% credible interval] Endocrine therapy alone 186,000 7.57 7.57 -- Ribociclib with endocrine therapy 442,000 7.76 7.79 1,200,000 [800,000 to 1,700,000]