Abstract PS3-13-02: Tumor Microenvironment in Asian-American and Native Hawaiian/Pacific Islander Women With Triple Negative Breast Cancer

Abstract Background: Triple negative breast cancer (TNBC) accounts for approximately 10-20% of breast cancer cases and has the worst overall survival and prognosis compared to other breast cancer subtypes. A higher percent of stromal tumor infiltrating lymphocytes (sTILs) in the tumor microenvironment (TME) of TNBC correlates with an improved prognosis. Also, high levels of TILs is associated with greater likelihood of pathologic complete response (pCR) in response to neoadjuvant treatment (NAT). Previous studies showed that all breast tumors from Asian Americans (AA) and Native Hawaiians and Pacific Islanders (NHPI) patients have a higher percent of sTILs compared to tumors from White patients. Although AAs have a lower cancer death ratio at 0.58, NHPIs have a higher cancer death rate ratio at 1.21 compared to White patients. Our study aims to molecularly characterize the tumor microenvironment in the AA and NHPI populations of patients with TNBC who received NAT. Methods: A retrospective chart review was conducted on 12 AA and 12 NHPI patient cases with early stage TNBC from 2015 to 2022 from a medical oncology clinic within the Hawai’i Pacific Health system. Breast cancer patient data collected included: age at diagnosis, histology, clinical stage, body mass index (BMI), sTILs, pCR, residual cancer burden, and NAT. Pre-treatment core biopsy samples were processed and gene expression profiles analyzed using the NanoString nCounter® Breast Cancer 360™ Panel and the nSolver Advanced Analysis Module. Differentially expressed genes (DEGs) and pathway analyses were generated using the ROSALIND® bioinformatics software. Results: Both AAs (66.7%) and NHPIs (58.3%) had a majority of the basal immunosuppressed (BLIS) TNBC subtype. When we compared TNBC tumors from AA and NHPI patients, 29 DEGs were statistically significant (p