Abstract Background: Social determinants of health (SDOH), the non-medical factors that influence health status, have a profound impact on breast cancer (BC) outcomes and contribute to survival disparities. Food insecurity (FI), defined as a lack of consistent access to adequate food resources, is a modifiable SDOH associated with treatment disruptions, medication nonadherence, and decreased quality of life. To identify at-risk patients and inform future interventions, we implemented SDOH screening of patients seen in breast oncology clinic at our urban academic medical center. Methods: Screening was conducted through an 8-item questionnaire on the electronic patient portal. The questions covered FI, housing and transportation challenges, and emergency department (ED) visits. We conducted a retrospective analysis of SDOH data collected among patients scheduled for a breast oncology appointment between 11/1/22 and 5/25/23. Any level of food hardship or concern constituted a positive FI screen. Descriptive statistics were used to determine the prevalence of FI and other SDOH, to assess differences in FI rates by age, race/ethnicity, and clinical stage, and to compare characteristics of food-insecure vs food-secure patients. We also conducted a multivariable logistic regression analysis to estimate the odds ratio (OR) and 95% confidence interval (CI) associated with sociodemographic/clinical factors and FI. Results: A total of 2,585 patients were seen in our breast oncology practice, of which 1,189 (46.0%) were screened for SDOH, including 41.2% non-Hispanic White (NHW), 9.6% non-Hispanic Black (NHB) and 21.0% Hispanic patients. Among patients who responded to each SDOH question, 15.5% (146/940) reported some level of FI; 8.7% (84/962) were unable to pay their rent or mortgage on time; for 5.8% (57/989), lack of transportation interfered with their treatment. The FI rate differed significantly by race and ethnicity: 4.5% of NHW, 15.2% of NHB, and 41.8% of Hispanic patients reported FI (p< 0.001). In multivariable analysis, NHB and Hispanic patients also had significantly higher odds of FI compared to NHW patients (OR=3.68, 95% CI=1.7-7.7, p< 0.001 for NHB and OR=15.0, 95% CI=8.8-27.1, p< 0.001 for Hispanic patients). Patients with metastatic disease had higher rates of FI compared to other breast oncology patients (23.6% vs 14.8%, p=0.048), and a metastatic BC diagnosis was associated with over twice the odds of FI (OR=2.18, 95% CI=1.1-4.2, p=0.02). Among food-insecure patients, 41.1% were unable to pay their rent or mortgage on time and 22.6% reported transportation difficulties interfering with treatment (vs 2.6% and 2.4%, respectively, for food-secure patients (p< 0.001)). Compared to food-secure patients, those who were food-insecure had significantly higher rates of self-reported ED visits in the past 12 months: 18.8% vs. 33.6% reported at least 1 ED visit, respectively, and 5.2% vs. 16.4% reported multiple ED visits, respectively (p< 0.001). Conclusions: In this analysis of SDOH data among patients seen in breast oncology clinic, FI was the most common social health risk reported, with nearly a quarter of patients with metastatic BC reporting FI. Racial/ethnic minorities were also at considerably higher risk for FI. ED utilization was significantly higher among food-insecure patients. Targeted interventions to reduce FI in at-risk populations are warranted to improve clinical and healthcare utilization outcomes. Sociodemographic and Clinical Characteristics and Other Reported Social Determinants of Health Among Food-Secure vs Food-Insecure Patients Citation Format: Claire Sathe, David DeStephano, Anita Gul, Melissa Beauchemin, Justine Kahn, Melissa Accordino, Katherine Crew, Ngozika Emezienna, Dawn Hershman. Prevalence of and Factors Associated with Food Insecurity and Other Adverse Social Determinants of Health Among Breast Oncology Patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-10-03.