Abstract PS5-05-29: Long-term impact of early-onset breast cancer in brazilian women: a real-world study of years of life lost and clinical outcomes

Abstract Introduction: Breast cancer is the leading cause of cancer-related death among women in Brazil and worldwide. However, its impact is not evenly distributed, with significant variations in incidence, mortality, and survival across different countries and regions. The incidence of breast cancer among young adults under the age of 50 has been increasing globally. This rise carries important implications both at the individual and societal levels, including a greater disease burden, reduced economic productivity, and an increased risk of long-term adverse clinical outcomes. There is a scarcity of data in the literature regarding this trend in Brazilian and Latin American populations. Objectives: We aimed to investigate the distribution profile of breast cancer diagnoses in adults under 50 years of age at two tertiary cancer centers in Brazil, as well as to compare it with the profile of patients aged 50 years and older, with a focus on clinical presentation and outcomes. Methods: We used real-world data from Einstein Hospital Israelita and Hospital Municipal Vila Santa Catarina between 2018 and 2023, including patients diagnosed with malignant breast neoplasms, according to the International Classification of Diseases - 10th Revision (ICD-10). Early-onset breast cancer was defined as a diagnosis in adults aged 18 to 49 years. Data extraction was automated using electronic medical record (EMR) systems and big data sources to obtain information related to ICD codes, demographic data, and medical history. For the calculation of years of life lost (YLLs), projected life expectancy was estimated for each individual based on their adjusted year of birth, sex, and place of residence, allowing for more precise and personalized estimates. Results: A total of 3,102 patients were analyzed, of whom 1,752 (56%) were aged 50 years or older and 1,350 (44%) were between 18 and 49 years old. Among the latter group, 28% reported their ethnicity, with the majority identifying as white (20%). Women accounted for 99.7% of the cases. Male sex was more frequent in the group aged 50 and older (1% vs. 0.3%; p=0.023). In the 18 to 49-year-old group, 61% of patients presented with localized or locally advanced disease (clinical stages I to III), while 39% had metastatic disease (clinical stage IV). Similarly, among patients aged 50 years or older, 59% were diagnosed at stages I to III, and 41% at stage IV. The median body mass index was lower in the younger group (24.6 kg/m2 vs. 26.1 kg/m2; p<0.001). Over the study period, there was an observed increase in breast cancer diagnoses among individuals aged 18 to 49, with a 10% rise in rates, from 4.47/10,000 in 2018 to 4.92/10,000 in 2023. In contrast, a 7.1% decrease was observed in the group aged 50 and older, from 11.97/10,000 in 2018 to 11.11/10,000 in 2023. Additionally, there was a higher proportion of germline testing among patients aged 18 to 49 (21% vs. 11%; p<0.001). When assessing years of life lost (YLLs), patients under 50 years of age exhibited a significantly higher burden, with a median of 42 years lost (IQR 37.5-46.0), in contrast to a median of 21 years (IQR 13.0-26.0) among those aged 50 and older. Conclusions: In line with global trends, the apparent increase in breast cancer cases among individuals under 50 years of age in Brazil raises hypotheses regarding both the rise in incidence and the possibility of distinct characteristics compared to those aged 50 and older. This pattern highlights the need for further investigations to better understand risk factors and to improve screening and management strategies for this age group. Citation Format: D. L. Miranda, D. Dias e Silva, B. Viesser Miyamura, U. Donizeti Rocioli Junior, P. Serrano Uson Junior, J. Rodrigues Beal, P. Taranto, J. Pontes Batista Cassoli, F. Moura. Long-term impact of early-onset breast cancer in brazilian women: a real-world study of years of life lost and clinical outcomes [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 PS5-05-29.