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

PURPOSE: Tumor-infiltrating lymphocytes (TILs) have emerged as a predictor of breast cancer treatment response and patient outcomes. Current studies investigating racial/ethnic differences in TILs and immune profiles in breast cancer offer varying results. Our study provides some preliminary data in the breast cancer tumor microenvironment where there is a paucity of information, from Asian and Native Hawaiian/Pacific Islander (NHPI) racial/ethnic groups, not well represented in the literature. METHODS: We reviewed 183 cases of women diagnosed with early stage breast cancer who received neoadjuvant treatment at 2 large health systems in Hawaii between 2008 and 2020. We evaluated clinical and demographic information including: age at diagnosis, self-reported race/ethnicity, tumor stage, tumor subtype according to ER, PR, and HER2 receptor status, the amount of TILs and pathologic complete response (pCR). RESULTS: We found a significantly greater amount of TILs in Asians (37.7%, P = .01) and NHPI (37.2%, P = .02) patients compared to White patients on multivariate analysis. We found no significant differences in pCR among the different racial/ethnic groups. CONCLUSIONS: Racial/ethnic differences in the amount of TILs in breast cancer tumors may suggest differences in the breast tumor microenvironment. This may in part contribute to known outcome disparities in these populations and should be further evaluated.