Abstract PS5-01-06: Contribution of Sociodemographic Characteristics to Treatment Delays in Patients with de novo Metastatic HER2-Positive Breast Cancer

Abstract Background: Outcomes for patients with de novo metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer have dramatically improved due to advances in HER2-directed therapy, yet significant disparities persist, with Black and Hispanic patients presenting with more advanced stage disease and experiencing worse survival outcomes compared to White patients. Studies suggest racial and ethnic minorities experience longer delays in treatment initiation, however large, comprehensive analyses of the impact of sociodemographic and clinical factors at the national level in the U.S. remain limited. Methods: We retrospectively identified patients diagnosed with de novo metastatic HER2-positive breast cancer between 2010 and 2022 using the National Cancer Database (NCDB). Clinical and sociodemographic characteristics were collected and compared across racial and ethnic groups. We categorized systemic therapy as chemotherapy alone or chemotherapy plus HER2-directed therapy. Treatment receipt and time to treatment initiation were evaluated by race/ethnicity. Multivariable linear regression was performed to examine sociodemographic differences in time to initiation of systemic and localized (i.e., radiotherapy) therapies, respectively. Beta coefficients reflected adjusted differences in treatment timing, with 95% confidence intervals (95% CI) reported. Results: A total of 27,972 patients with de novo metastatic HER2-positive breast cancer were included. Mean age was 58.8 years; 69.0% were White, 17.5% Black, 7.8% Hispanic, and 4.6% Asian/Pacific Islander (per self-report). At initial presentation, 9.5% had brain metastases, and 58.2% had visceral metastases. At the time of diagnosis, Black and Hispanic patients were younger, more often uninsured or Medicaid-insured, and more likely to reside in lower-education, lower-income areas (p0.001). While overall 88.5% of patients received a combination of chemotherapy and HER2-directed therapy, significant delays in treatment initiation were observed across all treatment modalities in minority groups. For systemic therapy, mean initiation times for Asian/Pacific Islander, White, Black, and Hispanic patients were 46.2 days, 47.2 days, 54.6 days, and 57.2 days, respectively (p0.001). Time to systemic therapy was significantly reduced in patients with visceral metastases, while brain metastases were associated with earlier radiation initiation (median 28 days to initiation in patients with brain metastases vs. 116 days in patients without brain metastases, p0.001). Adjusted analyses revealed that on average, Hispanic ethnicity was associated with a 7.3 day (95% CI: 3.2-11.4) delay in starting systemic therapy and 23.0 day (95% CI: 9.0-36.9) delay for radiotherapy initiation. Compared to White patients, Black patients had a 5.7 day (95% CI: 2.9-8.6) delay in starting systemic therapy and Asian/Pacific Islander patients had a 21.0 day (95% CI: 4.9-37.2) delay in starting radiotherapy. Lower education levels, lack of insurance, or having Medicaid/Medicare were also independent predictors of delayed initiation of systemic therapy, but interestingly not radiotherapy. Conclusion: In this U.S. national sample of patients with de novo metastatic HER2-positive breast cancer, substantial disparities persist in timely treatment initiation, particularly among Black and Hispanic patients, even after controlling for sociodemographic and clinical factors. Delays in this setting may adversely affect survival outcomes, highlighting the urgency of improving equitable access to care. Efforts must focus on enhancing health literacy, expanding insurance coverage, and improving care coordination infrastructure in disadvantaged communities. Citation Format: A. Ravichandran, M. Hennessy, J. Q. Freeman, S. Poland, W. Guo, R. Nanda. Contribution of Sociodemographic Characteristics to Treatment Delays in Patients with de novo Metastatic HER2-Positive Breast Cancer 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 PS5-01-06.