Cost-effectiveness analysis of ribociclib plus an aromatase inhibitor versus abemaciclib plus endocrine therapy in the adjuvant treatment of HR+/HER2- early breast cancer: a Canadian payer perspective

Aim: Ribociclib and abemaciclib, cyclin-dependent kinase 4/6 inhibitors, are adjuvant treatments for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) early breast cancer (EBC). In the Phase III NATALEE trial, ribociclib plus an aromatase inhibitor (AI) significantly improved invasive disease-free survival (IDFS) versus AI alone. This study assessed the cost-effectiveness of ribociclib plus AI versus abemaciclib plus endocrine therapy (ET) from a Canadian public payer perspective in high-risk HR+/HER2- EBC. Materials & methods: A nonhomogeneous, semi-Markov cohort model with six health states (IDFS, second primary malignancy, nonmetastatic recurrence, remission, distant recurrence and death) was developed from the Canadian healthcare system perspective using Ontario-based costs. The base case included direct medical costs over a lifetime horizon (49 years; starting age 52.4 years). The analysis focused on a subgroup of NATALEE patients who would have been eligible for abemaciclib based on the inclusion criteria of the monarchE trial. The primary comparator was abemaciclib plus ET and the secondary comparator included AI alone. IDFS was estimated using NATALEE data and was assumed to be the same between ribociclib and abemaciclib based on indirect evidence. Other transitions were informed by published sources. The base case was evaluated using probabilistic analyses, and outcomes included costs, life-years, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios. Results: Ribociclib plus AI yielded total lifetime costs of $155,277 (95% CI: $100,721 to $238,620) and total QALYs of 13.06 (95% CI: 12.33 to 13.83). In the comparison versus abemaciclib plus ET, ribociclib was less costly by $16,672, and had greater QALYs by 0.01. When comparing ribociclib plus AI versus AI alone, the estimated incremental cost-effectiveness ratio was $43,025 per QALY, with a difference in costs of $29,693 and a difference in QALYs of 0.69. Sensitivity analyses demonstrated that the results were most sensitive to the ribociclib medication costs and the IDFS hazard rate for AI. Conclusion: Ribociclib plus AI is cost-effective versus AI alone and cost-saving versus abemaciclib plus ET in persons with HR+/HER2- EBC who would meet the high-risk criteria from the monarchE trial.