Abstract PO3-05-03: Real-World Data on First-line Treatment of Hormone Receptor-positive, HER2-negative, Metastatic Breast Cancer in Brazil (BRAVE study - LACOG 0221)

Abstract Introduction: Endocrine therapy (ET) plus CDK 4/6 inhibitors is considered the standard of care as first-line therapy in hormone receptor positive (HR+)/HER2 negative (HER2-) metastatic breast cancer (mBC). Nonetheless, the use of chemotherapy (CT) is frequent in clinical practice, and access to CDK 4/6 inhibitors is limited in some countries. We used real-world data to describe treatment patterns, the impact of health insurance type, and outcomes among Brazilian patients with HR+/HER2- mBC treated in the first-line setting. Methods: In this observational retrospective study, female patients ≥ 18 years old diagnosed with de novo or recurrent HR+/HER2- mBC between January 2018 and December 2020 were included. Patients' data were extracted from medical charts or electronic health records (EHR). The primary endpoint was first-line treatment patterns in public and private health system cohorts. Key secondary endpoints were progression-free survival (PFS), defined as time from 1L treatment to progression or death, and overall survival (OS), defined as time from diagnosis of mBC until death or censoring. No formal statistical assumption was performed for sample size, the study recruited 2 cohorts of 150 patients from the public and 150 patients from the private health insurance system. Results: A total of 307 patients were included, 156 from public and 151 from private health insurance system, from 13 sites in Brazil. Median age was 56.8 (range 19.9-94.1), and 32.2% (N=99) had de novo MBC. Treatment patterns are described in Table 1. The most frequent treatment received in 1L was ET alone 42.4%, followed by CT (alone or CT followed by ET +- CDK4/6i) 31.6% and ET + CDK4/6i 25.1%. There was a significant difference between the 1L treatment with ET + CDK4/6i in the private and public systems, 48.3% vs 2.6%, p < .0001, respectively. The most frequently used CDK4/6i in 1L setting was Ribociclib (65.0%), followed by Palbociclib (36.9%) and Abemaciclib (7.1%). There was an increase in the use of CDK4/6i over time, 17% in 2018, 30.0% in 2019, and 27.9% in 2020. With a median follow-up of 32.2 months (95% CI: 29.4 - 34.4), the median 1L PFS was 22.9 months (95% CI: 16.9 - 25.2) in the public and 21.8 months (95% CI: 17.7 - 31.1) in the private health system, p=0.92. Median 1L PFS by treatment received was 13.6 months (95% CI: 6.1-39.0) with CT, 18.4 months (95% CI: 12.1-22.1) with CT followed by ET +-CDK4/6i, 21.9 months (95% CI: 17.3-25.5) with ET and 31.1 months with ET plus CDK 4/6i (95% CI: 15.8-42.8). Overall, median OS was 52.8 months (95%CI 49.4-NR). The 4-year OS rate per 1L treatment received were 50.3% (95% CI: 28.7-68.5) with CT, 39.0% (95% CI: 13.9-63.8) CT followed by ET +- CDK4/6i, 74.4% (95% CI: 58.0-85.1) with ET alone, 71.3% (95% CI: 49.6-85.0) ET + CDK4/6i, 50.3% (95% CI: 28.7-68.5) with CT and 39.0% (95% CI: 13.9-63.8) CT followed by ET +- CDK4/6i. Conclusion: ET is the most commonly used 1L treatment in clinical practice in Brazil, followed by ET + CDK4/6i and CT. A large difference in CDK4/6i use was observed between private and public health systems, reflecting the current limited access to CDK4/6i in Brazil. This study highlights treatment disparities within a nation with a fragmented health insurance system. Table 1. Treatment Patterns in Public and Private Healthcare Systems Citation Format: Gustavo Werutsky, Daniela Rosa, Tomás Reinert, Romualdo Barroso-Sousa, Heloísa Resende, Poliana Signorini, Eduardo Cronenberger, Juliana Góes Martins Fagundes, Jorge Henrique Santos Leal, Marina Dutra Giffoni, Aline Vieira, Luiza Nardin Weis, Jose Marcio Figueiredo, Tatiana Correa, Fernando Castilho Venero, Luisa Mostardeiro Tabajara Franche, Marina Musse Bernardes, Rafaela Jesus, Gustavo Gössling, José Bines. Real-World Data on First-line Treatment of Hormone Receptor-positive, HER2-negative, Metastatic Breast Cancer in Brazil (BRAVE study - LACOG 0221) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-05-03.