Racial/Ethnic Differences Among Tumor Infiltrating Lymphocytes in Breast Cancer Tumors

Abstract

PurposeTumor infiltrating lymphocytes (TILs) have emerged as a predictor of cancer treatment response and patient outcomes, including for breast cancer. Current studies investigating racial/ethnic differences in TILs and immune profiles in breast cancer offer varying results. Our study hopes to address the paucity of data in breast cancer tumor microenvironment from different racial/ethnic groups not well represented in the literature.MethodsWe reviewed 183 cases of women diagnosed with early stage breast cancer who received neoadjuvant treatment at two large health systems in Hawaii between 2008 and 2020. We evaluated clinical and demographic information including: age at diagnosis, race/ethnicity, tumor stage, tumor subtype according to ER, PR, and HER2 receptor status and compared them with obtaining a pathologic complete response (pCR) and amount of stromal TILs (sTILs).ResultsWe found a significantly greater amount of sTILs in Asians (37.7%, p=0.01) and Native Hawaiian/Pacific Islander (NHPI) (37.2%, p=0.02) patients compared to White patients on multivariate analysis. We found no significant differences in pCR among the different racial/ethnic groups.ConclusionsRacial/ethnic differences in the amount of sTILs in breast cancer tumors suggest that higher sTIL percentages alone do not predict for pCR. Increases in sTILs in Asian and NHPI patients suggest differences in immune cell profiles in the breast tumor microenvironment. This may in part contribute to known outcome disparities in these populations.