Abstract PS2-04-07: A large-scale, US-based study evaluating real-world medical cost savings and reduced healthcare resource utilization associated with longer first-line treatment for advanced breast cancer

Abstract Background Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) + aromatase inhibitor (AI) is the current standard of care for first-line (1L) treatment of hormone receptor (HR) +/human epidermal growth factor receptor (HER2−) advanced breast cancer (ABC). However, treatment resistance is common and affects 1L treatment duration, which may lead to higher healthcare expenditure due to disease progression and health deterioration. To better understand the association between medical costs and the duration of 1L treatment, this study investigated the real-world costs and healthcare resource utilization (HCRU) for patients with ABC who received 1L CDK4/6i + AI, stratified by the duration of 1L treatment (DoT). Methods This retrospective, observational cohort study extracted data from a large US claims database for commercially insured and Medicare Advantage patients diagnosed with ABC between April 2017 and August 2024. Eligible patients received CDK4/6i + AI as 1L treatment and had a follow-up of ≥6 months (m). Patients were grouped into two cohorts: ≤12 m DoT and 12 m DoT until cessation of both CDK4/6i + AI. Baseline characteristics were summarized using descriptive statistics. For patients with ≥12 m of follow-up (or less if due to death), medical costs and HCRU for the first 12 m from the start of 1L treatment were captured and calculated per patient per month (PPPM). Generalized linear models were used to analyze the relationship between DoT and medical costs/HCRU, adjusting for age, year of ABC diagnosis, comorbidities, and insurance type. Cumulative medical costs per patient were calculated in monthly intervals for the total study population according to DoT, from the start of 1L treatment to a maximum of 24 m. Results Among the 6464 patients in the study sample (mean age: 60. 9 years, 65. 0% commercially insured), 4546 had ≥12 m of follow-up (or less if due to death). Compared to patients with DoT 12 m (n=3830), those with DoT of ≤12 m (n=716) had higher mean PPPM costs (6, 424 vs 3, 645, p0. 0001) and HCRU in the 12 m following 1L start (Table). Cumulative medical costs per patient were 21, 126 lower for patients with DoT 12 m versus DoT ≤12 m at 12 m of follow-up, and 46, 479 lower at 24 m of follow-up. Key factors driving the medical cost savings in patients with DoT 12 m included reduced inpatient/outpatient care and fewer office visits. Conclusions Longer duration of 1L treatment was associated with reduced HCRU and substantial medical cost savings. Adoption of treatment approaches that prolong 1L DoT could meaningfully reduce the economic burden of cancer care. Citation Format: C. Chen, A. Ghosh, R. Potluri. A large-scale, US-based study evaluating real-world medical cost savings and reduced healthcare resource utilization associated with longer first-line treatment for advanced breast cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32 (4 Suppl): Abstract nr PS2-04-07.