Real-world costs of care and discontinuation among patients receiving adjuvant CDK4/6 inhibitors in early breast cancer.

Abstract

e12517 Background: For patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2–) early breast cancer (eBC) at high risk of recurrence, CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) are approved in the adjuvant setting. However, real-world data on treatment discontinuation and costs of care remain limited. Our study quantifies these outcomes in patients receiving adjuvant CDK4/6i in a real-world setting. Methods: We retrospectively identified adult women with newly diagnosed HR+/HER2− eBC who initiated abemaciclib or ribociclib in combination with ET in the adjuvant setting from 01/01/21–03/31/25 (initiation date = index date) using the IQVIA PharMetrics Plus database. Patients were required to have 12 months pre-index continuous enrollment (CE) and were followed from index until the earliest of end of CE, 12 months post CDK4/6i initiation, metastatic diagnosis code, or initiation of other therapy (metastatic treatment or PARP inhibitor). Discontinuation was defined as a gap of >60 days in CDK4/6i days’ supply based on pharmacy claims or a switch to PARP inhibitor. Costs of care (including outpatient costs, inpatient costs, emergency department costs, and pharmacy costs) were evaluated during the follow-up period for each patient. Costs were computed at a per patient per month (PPPM) level and then annualized. Results: A total of 1,338 patients were included. During the 12-month baseline period prior to CDK4/6i plus endocrine therapy (ET) initiation, mean total healthcare costs were $125,689.79. The mean time from breast cancer surgery to CDK4/6i initiation was 7.19 months. Based on Kaplan-Meier estimates, 31% of patients discontinued CDK4/6 inhibitor therapy within one year of initiation. The mean annualized per-patient-per-month (PPPM) total costs during follow-up were $209,524, driven primarily by pharmacy costs ($166,842), followed by outpatient costs ($32,527) (Table 1). Conclusions: This study provides current real-world costs of care and discontinuation estimates for patients who receive CDK4/6i in the adjuvant eBC setting. CDK4/6i discontinuation rates at 1 year were higher than those reported in clinical trials, which generally report lower discontinuation rates over longer follow-up, and were consistent with prior real-world evidence. Total PPPM costs are driven primarily by pharmacy and outpatient expenditures. PPPM annualized healthcare costs. Variable Mean (SD) Total Annualized Cost $209,524 (147,588) Inpatient (IP) Cost $9,674 (107,007) Emergency Room (ER) Cost $482 (1,607) Outpatient (OP) Cost $32,527 (46,682) Pharmacy (Rx) Cost $166,842 (94,434)