Cost-Effectiveness of Abemaciclib in Early Breast Cancer Patients: One Size Fits All or Tailoring to Patients' Needs?

Abstract

The addition of two years of abemaciclib treatment to standard adjuvant endocrine therapy in all patients with high risk ER+, HER2- early breast cancer (EBC) has been approved by the US Food and Drug Administration (FDA). Pre-selection of patients with an immediate risk of recurrence within the group of clinically high risk patients using detection of minimal residual disease (MRD) using patient-informed circulating tumor DNA assays during follow-up could enhance efficacy. Here, we investigate the cost-effectiveness of the addition of two years abemaciclib in all high risk HR+, HER2- patients and in MRD-guided high risk patients only. Two semi-Markov models were developed to evaluate the cost-effectiveness of adding two years of abemaciclib compared to "standard treatment": 1) "abemaciclib all" and 2) "MRD-guided abemaciclib" using MRD-guidance. Data of the MonarchE trial were used to model the invasive disease-free survival (iDFS). Since iDFS and overall survival (OS) data of abemaciclib were currently limited, abemaciclib effects were extrapolated using a favorable, intermediate and unfavorable effect scenario. The addition of abemaciclib in all high-risk EBC patients prolonged iDFS slightly (0.04 additional quality adjusted life years (QALYs)) and led to higher costs compared to standard ET, leading to a high incremental cost effectiveness ratio (ICER) of €1,551,876/QALY. Neither the favorable effect scenario (additional 1.09 QALYs) was cost-effective (ICER €62,935/QALY), using a willingness-to-pay threshold of €50,000/QALY. The "MRD-guided abemaciclib" strategy resulted in lower costs and an increase in QALYs (1.27) compared to "standard treatment" in the unfavorable effect scenario. The addition of abemaciclib to adjuvant endocrine therapy in all high-risk ER+, HER2- EBC patients is not cost-effective. However, using MRD detection to justify the addition of abemaciclib treatment dominates standard treatment in this cost-effectiveness analysis. Further evaluation of MRD detection in EBC by means of prospective clinical trials assessing clinical utility is recommended and promising in terms of cost-effectiveness.