Abstract C035: Immunotherapy for triple-negative breast cancer in the US: National trends, racial/ethnic disparities, and oncologic outcomes

Abstract Background: Triple-negative breast cancer (TNBC) is aggressive and disproportionately affects Black women. Immunotherapy (IO) improves outcomes in early-stage and metastatic TNBC and has been increasingly used since the accelerated approval of atezolizumab for metastatic TNBC in March 2019. However, whether there are racial/ethnic disparities in IO receipt and oncologic outcomes for TNBC is unclear. Methods: Data came from TNBC patients in the National Cancer Database. Trends in IO use were assessed from 2017-2021. For early-stage TNBC, we included stage II-III patients with neoadjuvant chemotherapy in 2021 and performed logistic regression to examine pathologic complete response (pCR) by race/ethnicity. In the metastatic cohort, patients diagnosed with TNBC from 2019-2021 were included and examined for racial/ethnic differences in overall survival using Cox regression. Racial/ethnic groups included American Indian, Alaska Native, or Other (AIANO), Asian or Pacific Islander (API), Black, Hispanic, and White. Results: Overall, IO use increased from 5.3% in 2017 to 33.1% in 2021 for metastatic TNBC and from 4.2% in 2017 to 48.0% in 2021 for early-stage TNBC (all P-trend.001). Of 7,655 early-stage TNBC diagnosed in 2021, 53.5% of API patients received IO, followed by 48.5% Hispanic, 48.3% AIANO, 48.2% White, and 45.9% Black. After controlling for demographic and clinical factors, there were no differences in IO use comparing API (adjusted odds ratio AOR=1.04; 95% CI=0.79-1.37), Hispanic (AOR=1.00; 95% CI=0.80-1.24), Black (AOR=0.96; 95% CI=0.83-1.12), AIANO (AOR=0.92; 95% CI=0.64-1.34) with White patients. However, Medicare enrollees had lower odds of IO receipt than those privately insured (AOR=0.84; 95% CI=0.70-0.99); comprehensive community programs had lower odds of IO use than academic/research programs (AOR=0.80; 95% CI=0.70-0.92). Among those who received IO, we found no difference in pCR rate by race/ethnicity. Of 4,533 metastatic TNBC diagnosed from 2019-2021, 35.4% of Hispanic patients received IO, followed by 34.3% API, 30.6% White, 26.7% AIANO, and 24.7% Black. In the adjusted model, Black patients with metastatic TNBC had lower odds of IO receipt than White patients (AOR=0.66; 95% CI=0.53-0.82) while no differences were observed between other minority and White patients. Among those who received IO, overall survival rates were similar between Black and White patients (adjusted hazard ratio=0.88; 95% CI=0.63-1.22). Conclusions: IO receipt was lower in Black patients with early-stage TNBC, which was influenced in part by facility type and insurance status – highlighting key targets to reduce these disparities. In the metastatic cohort, Black patients were less likely to receive IO even after confounder adjustment – etiologies of these disparities, such as inequitable treatment access or racial differences in PD-L1 status, require further exploration. In both cohorts, Black patients receiving IO attained equivalent outcomes to White patients, suggesting that access to IO can mitigate racial disparities in TNBC treatment outcomes. Citation Format: Jincong Q. Freeman, Dezheng Huo, Sarah P. Shubeck, Nan Chen, Sudha R. Yarlagadda, Rita Nanda, Frederick M. Howard. Immunotherapy for triple-negative breast cancer in the US: National trends, racial/ethnic disparities, and oncologic outcomes abstract. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C035.