Abstract PS4-08-25: Trends and determinants of non-treatment in early-stage breast cancer (ESBC)

Abstract Background: ESBC is curable, with established guidelines recommending timely multimodal management to optimize outcomes. Despite this, a subset of patients does not receive any form of cancer-directed therapy. Understanding the factors associated with non-treatment is essential. This study aims to evaluate contemporary, nationwide trends in non-treatment of ESBC and to identify factors associated with non-receipt of cancer care. Methods: We conducted a retrospective cohort study using data from the National Cancer Database (NCDB) to identify patients 18 years of age and older with clinical stage I-III breast cancer diagnosed between 2019 and 2022. We calculated annual rates of non-treatment (no surgery, chemotherapy, radiation, or hormone therapy for breast cancer) and assessed temporal trends across the study period. Univariate and multivariable logistic regression were used to identify clinical and sociodemographic factors associated with non-treatment, including year of diagnosis, age, race and ethnicity, clinical stage, breast cancer subtype, insurance status, among others. Results: Of the 579,005 patients with ESBC identified in the NCDB between 2019 and 2022, 13,631 (2.4%) patients received no cancer treatment. The annual rate of non-treatment was highest in 2019 (2.6%), but similar across 2020 (2.3%), 2021 (2.2%), and 2022 (2.3%). The mean age at diagnosis was 64 years for those patients who did not receive treatment and 61 years for those who did. Black (aOR=1.51, 95%CI 1.44-1.59) and Hispanic (aOR=1.18, 95%CI 1.10-1.26) patients were more likely to not receive treatment compared to White patients. Higher clinical stage (stage II-III vs. stage I), HER2-positive (aOR=1.24, 95%CI 1.18-1.31) and triple-negative breast cancer subtypes (vs. HR-positive/HER2-negative) (aOR=1.10, 95%CI 1.04-1.16) were associated with higher odds of non-treatment. Compared to those with private insurance, patients with Medicaid (aOR=1.31, 95%CI 1.23-1.40) or without insurance (aOR=2.70, 95%CI 2.45-2.97) were more likely to not receive treatment, while those with Medicare (aOR=0.90, 95%CI 0.86-0.95) were less likely. Higher education quartile and treatment in academic facilities were associated with lower odds of non-treatment. When compared to the lowest income quartile, those in the highest income quartile had similar odds of non-treatment (aOR=1.02, 95%CI 0.95-1.10). Conclusions: Despite overall low rates of non-treatment in ESBC, over 13,000 patients in our cohort did not receive any cancer-directed therapy, highlighting a significant opportunity to improve outcomes in patients with curable disease. Older age, Black and Hispanic race and ethnicity, lack of insurance, and treatment in non-academic centers were associated with higher odds of not receiving any cancer treatment. While these findings indicate persistent disparities in breast cancer care, further research is needed to better understand the extent to which non-treatment is driven by informed patient choice, clinical factors, or systemic barriers to accessing cancer care. Citation Format: M. Sullivan, X. Lei, I. Jackson, S. H. Giordano, M. Chavez-MacGregor. Trends and determinants of non-treatment in early-stage breast cancer (ESBC) 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 PS4-08-25.