Abstract PS5-11-12: Economic Impact of Adverse Event Management in HR+/HER2− Metastatic Breast Cancer: A Comparative Analysis of Datopotamab deruxtecan and standard of care in the Brazilian Private Healthcare System

Abstract Background: TROPION-Breast011 (TB01), a phase III clinical trial evaluated the safety and efficacy of datopotamab deruxtecan (Dato-DXd) in comparison to the investigator’s choice of standard single-agent chemotherapy (ICC). Dato-DXd demonstrated a manageable safety profile, characterized by a significantly lower incidence of grade ≥3 adverse events (AEs) compared to ICC (21% vs. 45%)1. Objective: This study aims to evaluate and compare the economic burden of managing grade ≥3 AEs in patients with HR+/HER2− metastatic breast cancer who have progressed on endocrine therapy and received at least one line of systemic. Methods: The therapeutic regimens analyzed in this study were derived from two pivotal clinical trials: TB01, which compared Dato-DXd with ICC: (capecitabine, eribulin, gemcitabine, vinorelbine), and TROPICS-022, which assessed sacituzumab govitecan (SG) versus ICC. AEs frequencies were extracted from the afore-mentioned clinical trials. To identify clinically and economically relevant events, a threshold of ≥10% frequency for any-grade AEs was applied, considering occurrences in each arm of the studies analyzed. Additionally, all grade ≥3 AEs were included regardless of frequency. Cost estimation was performed using a micro-costing approach3, incorporating direct medical expenses specifically associated with the management of grade ≥3 AEs. The total AE-related cost per treatment arm was calculated by multiplying the unit cost of each selected AE by its respective frequency and summing the resulting values. Results: The AEs selected for analysis are summarized in Table 1. Treatment with Dato-DXd resulted in an estimated AE-related cost of US$ 155.45, reflecting a 41.9% decrease in toxicity-related expenditures relative to its respective ICC arm comparator (US$ 267.36), while SG was associated with a total AE-related cost of US$ 535.66, compared to US$ 304.02 for its respective ICC arm comparator, indicating a 76.2% increase in costs related to adverse event management. Conclusion: This analysis identified differences in AE-related costs across treatment modalities, emphasizing the economic relevance of toxicity management in patients with HR+/HER2− metastatic breast cancer who have progressed on endocrine therapy and received at least one line of systemic treatment. Dato-DXd demonstrated lower expenditures associated with adverse event management compared to its respective ICC arm comparator. SG was associated with higher AE-related costs relative to its respective ICC arm comparator. These findings align with previous evidence, including the Ryczek (2024)4 study. The data highlights the importance of incorporating toxicity-related costs into treatment decision-making within the Brazilian Private Healthcare System. Citation Format: H. T. dos Santos, T. B. de Oliveira, A. B. Villa, C. d. Huerta, L. dos Santos, F. d. Costa, G. L. V. Araujo. Economic Impact of Adverse Event Management in HR+/HER2− Metastatic Breast Cancer: A Comparative Analysis of Datopotamab deruxtecan and standard of care in the Brazilian Private Healthcare System [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 PS5-11-12.