Abstract PS4-09-18: Factors with Immunotherapy Use Among Patients with Triple Negative Breast Cancer in California: A Population-Based Study

Abstract BACKGROUND: Immunotherapy with immune checkpoint inhibitors has been approved for triple negative breast cancer (TNBC) since 2019. However, uptake of new therapies may be delayed by a variety of factors that affect access, such as facility level factors and individual demographic factors such as race/ethnicity and age. We investigated individual-, facility- and neighborhood-level factors associated with use of immunotherapy among females diagnosed with TNBC in California from 2019-2021 using statewide cancer registry data. METHODS: We used the California Cancer Registry to identify 7,495 women ages 18 and over diagnosed with first primary microscopically confirmed malignant TNBC diagnosed in 2019-2021. We used registry data about immunotherapy use to infer use of immune checkpoint inhibitor. Patient-level factors include age at diagnosis, AJCC stage, grade, other treatments received, marital status, and health insurance status. We used multivariable logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI) factors associated with immunotherapy use, including independent variables that were statistically significant at p<0.1 for inclusion in the final logistic model. RESULTS: Overall, 16% (1,219 of7,495) women with TNBC received immunotherapy with use increasing from 7.8% in 2019 to 28.3% in 2021. In multivariable models, patient-level factors associated with lower likelihood of immunotherapy use included Non-Hispanic Black females (Non-Hispanic Black vs. Non-Hispanic White OR 0.61; 95% CI:0.47-0.80), earlier stage disease (Stage I vs. Stage IV OR: 0.14; 95% CI: 0.10-0.19), older age (Age >70 vs. Age <40 OR: 0.48; 95% CI: 0.39-0.61). Facility level factors associated with lower likelihood of immunotherapy use included no National Cancer Institute (NCI) designation status (non-NCI-designated vs. NCI-designated OR: 0.54; 95% CI: 0.43-0.67), facility with predominantly low socioeconomic status (low SES) patients (predominantly low SES vs. high SES OR: 0.61; 95% CI: 0.46-0.82). CONCLUSION: Use of immunotherapy among patients in California lagged among women seen at low SES hospitals, non-NCI designated facilities, and among older and Non-Hispanic Black patients. These results provide direction towards future research to better understand the patient, institutional, and neighborhood level barriers. Citation Format: J. Moya, A. Vu, L. Huppert, E. Ziv, S. Lin Gomez. Factors with Immunotherapy Use Among Patients with Triple Negative Breast Cancer in California: A Population-Based Study [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 PS4-09-18.