Cost effectiveness of CTC guided chemo or endocrine therapy in metastatic breast cancer. Results from a randomized controlled multicenter trial

Patients with metastatic, Estrogen Receptor (ER) positive, HER2-negative, breast cancer, before initiating CDK4/6 inhibitors, receive either single agent endocrine- or chemotherapy based on their clinical risk. In this first-ever trial-based economic evaluation of Circulating Tumor Cells (CTCs), the cost-effectiveness of standardizing the prescription of endocrine- or chemotherapy using a CTC count threshold (with >5 CTCs/7.5mL indicative of unfavorable disease outcomes) was compared to current clinical practice. N=755 ER+ HER2-patients, enrolled in 17 French centres, were randomized to CTC guided or standard of care and were treated according to either through the CTC score or clinical examination. Health state utilities were calculated by mapping the QLQ-C30 to EQ-5D utilities and used to calculate Quality-Adjusted Life Years (QALY) over a 2-year time horizon. Bootstrapping and additional sensitivity analyses were performed to quantify the impact of uncertainty. Health outcomes in both arms were similar, but costs were higher in the CTC guided arm ({euro}19,403) compared to the usual care ({euro}18,254), resulting in an ICER of {euro}104,078/QALY in favor of usual care. However, when the analysis was performed for the clinically high- and low-risk groups separately, CTC enumeration could be a dominant strategy (cost saving) if treatment is de-escalated in clinically high-risk patients as indicated by CTC scores. However, the current analysis was based on the PFS and OS data reported in 2021 and long-term Overall Survival data is collected since then (JCO, 2023 in press). A further analysis of the health economic impact of CTC enumeration in clinically low and high-risk groups is therefore indicated.