Factors associated with adjuvant chemotherapy initiation delays among breast cancer patients in a metropolitan healthcare system.

e12541 Background: Adjuvant chemotherapy initiation (ACI) delays in breast cancer patients are a critical concern, as they are linked to poorer survival outcomes. There are multiple factors associated with these delays, including patient-level factors (e.g., race, ethnicity, and insurance status), cancer-specific considerations (e.g., cancer stage and subtype), and system level barriers. Developing targeted interventions necessitates a greater understanding of ACI contributing factors. In this study, we examined factors associated with ACI delays among a cohort of women diagnosed with breast cancer in a metropolitan healthcare system. Methods: This study has been approved by the Social and Behavioral Research Panel of Northwestern University’s Institutional Review Board (IRB; study number STU00219464).Our cohort included people whose legal sex was female who had a first-time diagnosis of breast cancer receiving adjuvant chemotherapy at Northwestern Medicine between March 2022 and August 2025. Patient clinical and sociodemographic data were extracted from the Northwestern Medicine Electronic Data Warehouse. ACI delay was defined as a greater-than or equal-to-90-days interval between breast cancer surgery date and date of ACI. Multivariable logistic regression models were used to identify factors associated with ACI delay including race, ethnicity, insurance, area deprivation index (ADI) score, and cancer stage and subtype. Results: Of the 637 patients included in this analysis, the majority were White (80.8%), non-Hispanic (89.8%), had private insurance (57.9%), and stage I breast cancer (78.6%). The median number of days between breast cancer surgery and ACI was 47, and 10.4% (n = 66) of patients experienced ACI delay. Patients with higher odds of ACI delay identified as Hispanic (OR,2.0;95%CI,0.26-16.2), had Medicaid (OR,2.7;95%CI,0.33-21.7), stage III breast cancer (OR,7.71;95%CI,0.56-105.46), or progesterone receptor negative subtype (OR,3.82;95%CI,1.04-14.1). Patients who had lower odds of ACI delay identified as Black/African American (OR,0.24;95%CI,0.01-4.36), other race (OR,0.44;95%CI,0.03-6.02), or had Medicare (OR,0.33;95%CI,0.02-6.85). ADI score was not significantly associated with ACI delay (OR,0.98;95%CI,0.32-3.02). Conclusions: The present analysis indicated that Hispanic ethnicity, having Medicaid, stage III breast cancer, and progesterone receptor negative subtype were associated with higher odds of ACI delay when compared with their respective reference groups, while non-White race and having Medicare was associated with lower odds of ACI delay. These findings can be used to guide in the development of interventions that address barriers to timely ACI.