Abstract PS3-10-04: Characteristics of patients with HR+/HER2− early breast cancer eligible for adjuvant treatment with iCDK4/6: real-life evidence in a Colombian cancer center

Abstract Background: The introduction of CDK4/6 inhibitors (iCDK4/6) in the adjuvant setting for hormone receptor-positive (HR+)/HER2-negative (HER2-) early breast cancer has expanded treatment options for high-risk patients. However, real-world data on eligibility for these therapies in Latin American populations remain limited. Methods: This retrospective study analyzed 334 patients with HR+/HER2- early breast cancer (stages I-III) treated at a Colombian cancer center (2022-2024). Eligibility criteria for adjuvant abemaciclib (monarch-E) and ribociclib (NATALEE) were applied. Clinicopathological characteristics and treatment patterns were assessed. Results: Among abemaciclib-eligible patients (36.2%, n=121), 54.5% had ≥4 positive nodes and 45.5% met alternative high-risk criteria (1-3 nodes plus tumor size ≥5 cm or grade 3 or Ki67 ≥20%). Ribociclib-eligible patients (59%, n=197) included 53.8% with stage III disease and 12.7% with node-negative, grade 3 tumors. Compared to pivotal trials, our cohort had older median age (61 vs 51-58 years) and lower prevalence of grade 3 tumors (17.1% vs 30-40%). Conclusion: A substantial proportion of Colombian patients with early HR+/HER2- breast cancer qualify for adjuvant CDK4/6i, particularly those with nodal involvement. These findings highlight both the clinical opportunity and economic challenges of implementing these therapies in resource-limited settings, while underscoring the need for improved early detection to reduce advanced presentations. Citation Format: A. S. Golemba, S. P. Rodriguez Torres, R. F. Vargas Moranth, P. Mandó, A. A. Aguirre Santamaria. Characteristics of patients with HR+/HER2− early breast cancer eligible for adjuvant treatment with iCDK4/6: real-life evidence in a Colombian cancer center. 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 PS3-10-04.