Early-onset (EO) cancer trends in Brazil: A comprehensive analysis of hospital-based cancer registry data (2000–2019).

10552 Background: The rising incidence of early-onset (EO) cancers (< 45 years) since the 1990s presents a global public health challenge. In Brazil, Hospital-Based Cancer Registries (HCR) provide essential data for understanding cancer epidemiology, encompassing diagnosis, treatment, and outcomes. This study analyzes temporal trends in EO cancer incidence rates (IR) and clinical data in Brazil from 2000 to 2019. Methods: A retrospective cohort study was conducted using data from the Brazilian HCR system (SIS-RHC). Individuals aged 19–44 years, diagnosed with malignant neoplasms (ICD-10) and treated within Brazil’s oncology network, were included. Temporal trends in cancer incidence (2000–2019) were evaluated using the Mann-Kendall test, and bivariate analyses explored associations between demographic and clinical variables. Results: A total of 701,115 individuals were included (mean age: 35 years, SD: 6.62); the cohort was predominantly female (71.9%), non-white (54%), with basic education (49%), and residing in the southeast region (44%). Family history of cancer was reported by 47%, alcohol use by 28%, and smoking by 29%. The Unified Health System (SUS) referred to 79% of cases. Breast (21%) and cervical (21%) cancers were the most prevalent malignancies, followed by non-melanoma skin cancers (8.8%) and thyroid cancer (7.3%). Colon cancer ranked seventh (2.8%). Most cases were diagnosed at localized stages (51.7%), with 28.3% regional and 19.8% metastatic. Localized diagnoses increased significantly over time. Sex differences were observed across age groups and cancer stages (p < 0.001). Annual cancer cases rose significantly from 93,714 cases (2000 to 2004) to 222,301 cases (2015 to 2019) (p < 0.001). Incidence rates (IR) increased with age and over time, rising from 5.65 (ages 19–24) and 46.80 (ages 40–44) in 2000 to 12.28 and 77.11 in 2019. Peaks in IR were observed in 2014 and 2016, reaching 17.41 (ages 19–24) and 111.42 (ages 40–44). Overall, reported cases increased by 219% during the study period. Conclusions: The incidence of EO cancers in Brazil rose by 219% between 2000 and 2019, with breast cancer as the leading malignancy. These findings emphasize the growing cancer burden among younger populations and the need for enhanced cancer registries to guide targeted EO interventions. Future population-based studies are critical to validate and expand upon these results.