Abstract Background: Advance care planning (ACP) is a process that supports adults at any age or stage of health in understanding and sharing their personal values, life goals, and preferences regarding future medical care. Likewise, ACP is associated with multiple benefits, such as lower rates of hospitalizations and reduced futile, aggressive cancer treatment at the end of life. However, ACP rates remain low in the U.S., especially for patients with advanced cancer. Despite being more likely to be diagnosed at advanced stages and hospitalized due to advanced cancer with poor prognosis, the Black and Hispanic/Latino populations continue to have meager rates of ACP. Research has shown that both individual-level and systems-level factors contribute to these racial disparities in ACP. Considering these disparities among vulnerable populations, interventions that increase ACP among minority patients with cancer are needed. Objective: To analyze using multilevel model analysis the predictors of ACP documentation in female patients with breast cancer over 5 years in the UChicago Health System. Methods: Using the Clinical Data Research Warehouse, this study included women diagnosed with breast cancer (N=7,814) from 2016 to 2021. Descriptive statistics were performed to characterize ACP, and potential differences in ACP rates among control variables were assessed using odds ratio (OR) estimations. Significantly correlated variables were included as covariates in the multivariate analyses through a logistic regression model. The multilevel random-effects (mixed-effects) model, using restricted maximum likelihood estimation, examined the pattern of ACP documentation; in the multilevel model, level 1 modeled the changes in individual ACP documentation, and level 2 included the between-subjects effects of the predictors of documentation. Results: 13.76% of women with breast cancer filled out at least one type of ACP documentation, 4.25% filled out the Power of Attorney, 5.75% filled out the Advance Directive, and 8.92% filled out the Code Status. Increasing age and being black/African-American seem to be related to an increased likelihood of completion of at least one type of ACP documentation. While increasing BMI and outpatient services seem to be related to a decrease in the likelihood of completing at least one type of ACP documentation. Conclusion: Understanding the factors related to ACP documentation will allow us to manage them and improve their completion. These results will help to inform the development of tools to increase the integration of ACP into care, especially those that are technology-based. Further work could include designing a predictive model to prioritize patients requiring ACP. Providing knowledge about ACP in nonclinical areas can lead to increased education about ACP and its benefits to families and communities. Citation Format: Andres Mauricio Garcia Sierra, Marcia Tan. Predictors of advance care planning documentation in female patients with breast cancer: A multilevel model analysis [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C005.