Abstract PS4-11-18: Financial Toxicity in Breast Cancer Patients Assessed by the COST Score: A Systematic Review and Meta-analysis

Abstract Background: Financial toxicity (FT) refers to the negative impact on patients and their families caused by significant financial strain resulting from the diagnosis or treatment of illnesses such as cancer. This effect can significantly affect their quality of life, survival, or daily functioning. The Comprehensive Score for Financial Toxicity (COST) is a validated patient-reported outcome measure developed to assess FT in cancer patients. COST scores range from 0 (worst FT) to 44 (no FT). The tool has been translated into over 30 languages and is now used globally in diverse healthcare systems. Breast cancer is associated with a high risk of FT due to prolonged treatment duration, long-term toxicities, and its frequent occurrence in working-age women. Although many studies have evaluated FT in this population, reported prevalence and methodological approaches vary widely. This study aims to determine the FT rate among breast cancer patients using the COST tool and to identify particularly vulnerable patient populations. Methods: A systematic review and meta-analysis (registered in PROSPERO, ID 1084262) was performed following PRISMA guidelines. Searches were performed in PubMed, Cochrane, LILACS and Embase. Eligible studies included breast cancer patients assessed with the COST tool. Data on FT prevalence and mean or median COST scores were extracted. Random-effects models were used to calculate pooled estimates. Heterogeneity was quantified using the I2 statistic. Meta-regression and a bubble plot were used to assess temporal trends. The Newcastle-Ottawa Scale was used to assess the risk of bias. Results: Thirteen studies published between 2016 and 2024 were included, representing over 8,400 patients across China (n=5), the United States (n=6), South Korea (n=1), and Indonesia (n=1). Sample sizes ranged from 99 to 4,297. Most participants were women of working age, with ages ranging from 43 to 58 years. Educational background and employment status varied widely, with employment rates ranging from 7.7% to 70%. Insurance types reflected local health system structures, including public, private, and uninsured populations. Systemic therapies commonly include chemotherapy, endocrine therapy, and targeted agents. The pooled prevalence of FT was 66.9% (95% CI: 45.1-88.7%; I2 99.9%). The pooled mean COST score was 23.87 (95% CI: 21.25-26.50; I2 99.8%), reflecting moderate financial distress. A slight but non-significant decrease in COST scores over time was observed (regression coefficient: -0.40; 95% CI: -1.46 to 0.66; p = 0.432), suggesting a possible worsening of FT in recent years. No study was classified as having a "high risk" of bias. Conclusion: FT is highly prevalent among breast cancer patients, with a moderate burden as observed in COST scores. These findings highlight the need for targeted financial support strategies and health policy interventions to mitigate FT, particularly in vulnerable populations. Keyword: Breast cancer; Financial toxicity; COST; Meta-analysis; Systematic reviews. Citation Format: N. C. Nunes, J. da Silva, K. S. de Medeiros, G. Hora, M. Teixeira, L. Leite, L. Zanetti, B. Linhares, A. de Melo. Financial Toxicity in Breast Cancer Patients Assessed by the COST Score: A Systematic Review and Meta-analysis 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 PS4-11-18.