Economic impact of longer treatment duration in first-line for HR+/HER2- metastatic breast cancer: A retrospective analysis.

1072 Background: Real-world treatment duration (TD) in the first line of therapy (1LOT) has demonstrated a strong correlation with progression-free survival (PFS). Increased TD for cancer patients (pts) in earlier lines has been linked to reduced healthcare costs by mitigating the need for costly therapies in subsequent lines, but the extent to which 1LOT costs vary based on the duration pts stay on treatment in 1LOT remains largely unknown. This study investigates the relationship between the TD of endocrine therapy (ET) plus CDK4/6 inhibition (CDKi) in 1LOT (serving as a proxy for PFS) and various healthcare cost measures incurred in 1LOT among newly diagnosed pts with HR+/HER2- metastatic breast cancer (mBC). Methods: Using the IQVIA PharMetrics Plus database, we identified adult women with newly diagnosed HR+/HER2- mBC whose 1LOT within 90 days of metastatic diagnosis (met dx) was ET + CDKi between 10/01/2016 - 06/30/2022. Pts with at least 6 months of follow-up post-met dx were included. The study followed pts from ET+ CDKi initiation until a switch, discontinuation, or a gap exceeding 90 days. Baseline characteristics were assessed 12 months before met dx. Healthcare costs (adjusted to 2022 USD) during the follow-up period were measured per patient per month (PPPM). TD was categorized based on percentile (p) distribution into six groups (<10p; ≥10p to <25p; ≥25p to <50p; ≥50p to <75p; ≥75p to <90p; and ≥90p). Cost measures included total, inpatient (inp), outpatient (outp), ER, and pharmacy (rx) costs. Generalized linear and two-part models examined the relationship between various cost measures and TD, adjusting for age, region, payer type, and Elixhauser comorbidity index (ECI). Results: The study included 1, 536 pts receiving ET+ CDKi in 1LOT, with a median age of 59. The median ET + CDKi TD in 1LOT was 23. 7 months. PPPM costs were 18, 716; 1, 044; 2, 899; 63; and 14, 711 for total, inp, outp, ER, and rx services, respectively. Models results indicate lower PPPM total, inp, outp and ER costs as TD increases (Table). PPPM costs were higher for the bottom 10th p (shortest TD group) compared to the top 10th p (longest TD group) (difference 6, 411; 2, 735; 3, 297; and 205 higher for total, inp, outp, and ER visits respectively). PPPM rx costs did not vary with TD. Conclusions: Real-world TD of ET+ CDKi closely aligns with PFS reported in ET + CDKi trials, further demonstrating a strong correlation with PFS. Prolonging TD in 1LOT yields significant cost savings, primarily driven by reductions in inp, outp, and ER costs. The results underscore the need for ongoing optimization of pts selection for 1LOT for HR+ mBC. The study findings also suggest that the economic evaluation of investigated treatments should take into account treatment duration. Table: see text