Abstract PS1-12-06: Ribo-age: age-stratified descriptive analysis of adverse drug reactions in patients with advanced breast cancer treated with ribociclib plus nonsteroidal aromatase inhibitors: preliminary results

Abstract Background: Ribociclib (RIB), a CDK4/6 inhibitor, in combination with endocrine therapy (ET), has demonstrated significant improvements in progression-free survival (PFS) and overall survival (OS) in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2−) advanced breast cancer (ABC), as evidenced by the MONALEESA phase III trials. Despite these robust clinical trial outcomes, to our knowledge, real-world data on safety and tolerability of RIB + ET, in the Spanish healthcare setting, remain scarce. This study aims to address this gap by evaluating the safety profile of RIB in combination with a non-steroidal aromatase inhibitor (NSAI) as first-line (1L) therapy in both younger and older patients with HR+/HER2− ABC, based on routine clinical practice in Spain. In this report, we show a preliminary result from the first 147 patients. The final analysis will include at least 500 patients. Methods: This is a non-interventional, retrospective cohort study involving patients diagnosed with HR+/HER2− ABC who initiated 1L treatment with RIB + NSAI between January 2021 and August 2023. Data was collected exclusively from medical records across participating centers. Following the final patient inclusion date, a subsequent 12-month follow-up period (until August 2024) is established to ensure adequate exposure to RIB across all participants and to monitor the potential emergence of adverse events (AEs). If discontinuation occurs for any reason, the duration of exposure to RIB was measured. Results: The median follow-up was 23.8 months (range: 3.1 - 43.4), and the median time on treatment was 18.39 months (range: 0.5 - 43.4). Stratified by age, the PFS rate at 24 months was 63.3% (95% CI: 52.6 - 72.3) in patients aged ≤ 65 years and 65.5% (95% CI: 47.0 - 78.9) in those aged > 65 years. In general, the safety profile was consistent with previously reported data, with no new safety signals. From 141 patients reporting at least one AEs, 16 discontinued RIB due to AEs (10.9% of the whole population). The two most common AEs for both, safety and tolerability are summarized in Table 1. Conclusions: Preliminary real-world data suggest that RIB + NSAI is well tolerated in both younger and older patients with HR+/HER2− ABC in the Spanish healthcare setting. PFS outcomes appear consistent across age groups. Final results from the full set of at least 500 patients will provide more definitive insights into the safety profile and treatment outcomes. Citation Format: T. Díaz-Redondo, R. Sánchez-Bayona, P. Zamora Auñon, I. Garcia-Fructuoso, A. Bujosa, J. Sánchez, J. Ponce Lorenzo, A. Jiménez Ortega, E. Marin Olivo, A. Corbera, A. López. Ribo-age: age-stratified descriptive analysis of adverse drug reactions in patients with advanced breast cancer treated with ribociclib plus nonsteroidal aromatase inhibitors: preliminary results [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 PS1-12-06.