Sociodemographic and clinical determinants of survival in metastatic breast cancer: A population-based analysis from a Latin American developing country.

e13125 Background: To evaluate the impact of tumor, treatment, and sociodemographic factors on overall survival (OS) and cancer-specific survival (CSS) in metastatic breast cancer (mBC) using a population-based database from a Latin American developing country. Methods: Patients diagnosed with de novo MBC from 2000 to 2023 were identified in the Fundação Oncocentro São Paulo (FOSP-Brazil) database. OS and CSS were estimated using the Kaplan-Meier method and stratified by treatment, tumor, patient, and sociodemographic characteristics. Cox proportional hazards models were used to identify factors associated with OS and CSS. A Sociodemographic Index (SD-I) was developed to assess its impact on survival outcomes. Results: A total of 14,588 patients were included. The 1-, 3-, and 5-year OS rates were 64%, 32%, and 18%, respectively, while CSS rates were 67%, 36%, and 22%. In multivariate analysis (MVA), significant predictors of OS and CSS included the number of metastatic sites (p < 0.001), radiotherapy to metastases (p < 0.01), educational level (p < 0.01), treatment delay (p < 0.001), public healthcare access (p < 0.01), and treatment center complexity (p = 0.001). Patients were stratified into high, mid, low, and very low SD-I categories based on significant sociodemographic factors. The 5-year OS rates for high, mid, low, and very low SD-I groups were 23.5% (95% CI: 17-33%), 18.6% (95% CI: 17.2-22.1%), 17.3% (95% CI: 16.5-18.2%), and 14.7% (95% CI: 10-21.7%), respectively (p < 0.001). Similar trends were observed for CSS (p < 0.001). Conclusions: This study identifies critical factors influencing survival in MBC and underscores the impact of sociodemographic disparities (SD-I), highlighting the need for targeted interventions to address healthcare inequalities.