Abstract PS5-12-01: Breast cancer in chile: incidence rising, young women dying, why?

Abstract Introduction In Chile, official databases on mortality and hospitalizations systematically record all events, identifying causes using the ICD-10 coding system. Since 2005, the Explicit Health Guarantees (GES) program has provided time-bound treatment and financial coverage for specific conditions, including breast cancer (BC). In 2024, we conducted a descriptive-analytical study using official secondary databases from Chile, covering mortality from 1997 to 2023. We found that the BC mortality rate increased by 19.2% among women under the age of 40, while it decreased by 21% among women aged 40 and older. Objective: To describe the incidence of BC in Chile, with a specific focus on women under 40 years of age. Materials and methods: This is a descriptive study. For incidence, data from the GES program were used as a proxy. We analyzed the period between 2007 and 2023. All data sources had near-complete national coverage. The study variables included: Temporal trends (year of event) through Annual Percentage Change (APC), individual characteristics (age), and disease coding using ICD-10 code “C50” for BC. Due to the case distribution, incidence trends were examined annually. Crude and age-adjusted rates were calculated. Temporal trends were assessed using Joinpoint regression models (Version 5.2). Data were processed using R software (2023). Results According to GES data, from 2007 to 2023: • The number of new BC cases in women under 40 increased with an APC of 7.42% between 2014 and 2023. • Among women aged ≥40, incidence rise of BC by an APC of 9.94% between 2020 and 2023. • The crude incidence rate of BC per 100,000 women aged 20-39 increased from 8.7 in 2007 to 19.75 in 2023 (+227%), indicating a concerning upward trend among younger women. • For women ≥40, the crude incidence rate of BC rose from 104.82 in 2007 to 162.00 in 2023 (+154%). • Among women under 40 years old, the APC was 4.82, indicating a faster rise in incidence rates between 2007 and 2023. In contrast, women over 40 years old experienced a more gradual increase, with an APC of 2.15 Conclusions At SABCS 2024, we reported a 19.2% increase in BC mortality among women under 40, with this trend accelerating after 2015, while mortality decreased by 21% in women over 40. In this report, we present incidence data from 2007 to 2023, revealing a faster rise among younger women. It is important to note that the increase in mortality among women <40 is not solely explained by rising incidence. While both age groups have experienced increasing incidence, the magnitude and associated mortality differ. Further research is needed to identify other contributing factors to mortality in women under 40, including lifestyle changes, comorbidities, healthcare access, and educational disparities. Although breast cancer policies in Chile have led to favorable outcomes for women over 40, similar progress has not been observed in younger women, emphasizing the need for age-specific strategies targeting this demographic. Citation Format: C. Salas, Y. Bernal, I. Delgado. Breast cancer in chile: incidence rising, young women dying, why? [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 PS5-12-01.