Abstract PS2-06-26: Sociodemographic and Clinical Factors Associated with Late-Stage Breast Cancer in Young Brazilian Women: A 23-Year Nationwide Study of 52,734 Patients

Abstract Introduction: Cancer in adolescents and young adults (AYAs), aged 15 to 39 years, constitutes a major global health challenge, with over 1.2 million new cases diagnosed each year. As a consequence, AYAs are frequently diagnosed at more advanced stages and experience worse clinical outcomes compared to other age groups. In young women, breast cancer (BC) represents a major contributor to cancer-related illness and death. Objective: To determine the frequency and identify sociodemographic and clinical factors associated with late-stage BC diagnosis among young women treated within Brazil’s public healthcare system. Methods: A secondary database study was conducted, including women aged 15 to 39 years who were diagnosed and treated for BC (ICD-10 C50) within Brazil’s public healthcare system, as recorded in the national Hospital Cancer Registry between 2000 and 2023. Non-analytic or lacking clinical stage information cases were excluded. The primary end point was late-stage diagnosis, defined as clinical stage III or IV at presentation. Sociodemographic and clinical variables were collected for analysis. Descriptive analysis was performed, and multivariable logistic regression using the Stepwise Forward method was applied to identify factors associated with the outcome. Variables with a p-value 0.05 were retained in the final model. Results: Among the 52,734 eligible patients, 0.1% were aged 15-19 years (n = 39), 12.2% were aged 20-29 years (n = 6,431), and 87.7% were aged 30-39 years (n = 46,264), with a median age at diagnosis of 35 years (SD ±3.93). The majority self-identified as Black or mixed-race (55.3%), 54.3% reported being in a partnered relationship, and 59.5% had ≥9 years of formal education. Half of the cases were reported from the Southeast region (50.7%). At the time of diagnosis, 8.4% of patients reported alcohol consumption, and 6.1% were current smokers. The predominant histological subtype was invasive carcinoma of no special type (80.6%). Most patients (78.7%) were referred for treatment via the public healthcare system. In multivariable logistic regression analysis, independent factors associated with late-stage diagnosis included younger age (OR 0.97; 95% CI, 0.96-0.98; p 0.001), Black or mixed-race ethnicity (OR 1.34; 95% CI, 1.24-1.42; p 0.001), lower educational attainment (OR 1.27; 95% CI, 1.20-1.34; p 0.001), unpartnered status (OR 1.12; 95% CI, 1.06-1.18; p 0.001), invasive carcinoma of no special type (OR 1.62; 95% CI, 1.48-1.76; p 0.001), and referral through the public health system (OR 1.34; 95% CI, 1.25-1.43; p 0.001). Alcohol consumption, tobacco use, and geographic macroregion were not significantly associated with stage at diagnosis. Conclusion: This nationwide cohort study of over 50,000 young Brazilian women with breast cancer—one of the largest to date—shows that late-stage diagnosis remains common, affecting nearly 40% of patients. Advanced-stage disease was independently associated with Black or mixed-race ethnicity, low educational level, unpartnered status, invasive carcinoma of no special type, and referral through the public health system. These findings underscore the impact of social vulnerability on cancer staging and persistent inequities in timely access to care. Targeted public health strategies addressing social determinants, early symptom recognition, and equitable access to services are critical to reduce disparities and improve outcomes in this high-risk group. Citation Format: A. Pires, A. Bergmann, C. Resende, L. Thuler, M. Bello, G. Bretas, A. Gonçalves. Sociodemographic and Clinical Factors Associated with Late-Stage Breast Cancer in Young Brazilian Women: A 23-Year Nationwide Study of 52,734 Patients 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 PS2-06-26.