Abstract A028: Disparities in suppressive immunity in Hispanic/Latina patients with hormone receptor positive breast cancer
Authors: Carrel Sabrina , Li Michelle , Al-Zubeidy Batul , Zavala Dominic , Gonzales Edgar , Baugh Aaron , Castanon Sofi , Hsu Robert , Sidiropoulos Dimitrios N , Ma Yanling , Press Michael , Torres Evanthia T Roussos 
Published: February 2024

Abstract
In the US, breast cancer is the number one cancer diagnosed, and it is responsible for the most cancer related deaths among Hispanic/Latina (H/L) women. The mean age of diagnosis of breast cancer in H/L patients is 3.7 years younger than their Non-Hispanic White (NHW) counterparts. Despite being diagnosed with breast cancer at a younger age, the H/L population has a better overall survival rate across all breast cancer subtypes. This study investigates whether the immune response mounted against tumor cells in the H/L population differs from that mounted by NHW patients. We recruited and received consent from patients diagnosed with stage I- III (early stage), or stage IV/advanced (metastatic), hormone receptor positive (HR+) breast cancer. We collected blood from 66 patients (38 H/L, 28 NHW) across all stages of disease, and tumor tissue from 14 unmatched patients (7 H/L, 7 NHW), with early stage disease, at the time of tumor resection, none of whom had received neoadjuvant chemotherapy. We utilized multiparameter flow cytometry to analyze peripheral blood mononuclear cells (PBMCs), and 10X Visium for spatial transcriptomic and proteomic evaluation of patient’s tumor tissue to characterize differences in immune composition by race. We hypothesize that evaluation of intra-tumoral immune composition will reveal fewer immune suppressor cells and increased infiltration of cytotoxic immune cells in tumors from H/L patients. We also hypothesize evaluation of immune cells in circulation will mirror findings from within tumors. Suppressor immune cells, comprised of M2-polarized macrophages, myeloid derived suppressor cells (MDSCs), and T regulatory cells (Tregs) modulate T cell proliferation and cytotoxicity to affect anti-tumor immunity. We report a significant difference in the levels of both anti-tumoral and suppressive immune cells in the periphery within the H/L patient population when comparing early vs. metastatic HR+ breast cancer. This was not observed in the NHW group and there were no differences when comparing peripheral suppressor and T cell populations in H/L vs. NHW at any stage. Comparisons of intra-tumoral immune cell infiltration and differences in transcription profiles are forthcoming. The findings from this study will be some of the first to look at the immune composition in H/L women with HR+ disease, and could provide data to support larger studies leading to a paradigm shift in how we approach clinical trial design for immune checkpoint inhibition.
Citation Format: Sabrina Carrel, Michelle Li, Batul Al-Zubeidy, Dominic Zavala, Edgar Gonzales, Aaron Baugh, Sofi Castanon, Robert Hsu, Dimitrios N Sidiropoulos, Yanling Ma, Michael Press, Evanthia T Roussos Torres. Disparities in suppressive immunity in Hispanic/Latina patients with hormone receptor positive breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A028.