Abstract P6-06-13: Racial/ethnic differences in tumor infiltrating lymphocytes

Background/Rationale: There have been increasing studies regarding the morphologic evaluation of tumor-infiltrating lymphocytes (TILs) and the tumor microenvironment. In breast cancer, TILs are more abundant in stroma (sTILs) compared to intratumoral (iTILs) areas and iTILs have been an unreliable marker due to difficulty in standardizing their evaluation. The International Immuno-Oncology Working Group published recommendations to guide the accurate assessment of TILs. TILs have relevance in the setting of neoadjuvant therapy (NAT), primarily in triple negative and HER2 positive breast cancers. Studies report that sTIL infiltration is predictive of response to NAT in these two breast cancer subtypes, but not in the estrogen positive breast cancer subtype. The presence of TILs is a good prognostic indicator and correlates with axillary lymph node negativity, lower histological grade and improved recurrence-free survival. Therefore, evaluating TILs prior to NAT can provide important predictive and prognostic information for clinicians. There are insufficient data exploring differences in sTILs among different racial/ethnic groups. Previous data showed Asians had more sTILs compared to White and African American patients, consistent with data from Asia that found substantial sTILs in their respective patient populations. Our diverse population has known racial/ethnic disparities, where Pacific Islanders have a higher mortality compared to Asian and White patients. Evaluating sTILs within this population may reveal tumor biology differences that could contribute to health disparities. Research objectives: To determine the stromal tumor infiltrating lymphocytes on core biopsy specimens and correlate them with clinical characteristics: ethnicity, age, BMI and stage To determine differences in pathologic complete response (pCR) with ethnicity, age, BMI, neoadjuvant therapy and stage Results: We evaluated 57 neoadjuvant breast cancer cases for sTILs according to the International Immuno-Oncology Working Group recommendations and reviewed their clinical characteristics. We found significant % sTILs differences in ethnicity, specifically Asian (35%), Pacific Islander (38.5%) and Other (46%) category compared to White (19%) Table 1. There were no differences found in sTILs according to age, BMI or stage. We also found no significant pCR differences according to age, BMI or ethnicity, however for certain stages and neoadjuvant therapy, there is an increased rate of pCR, although these are a small number of cases, no conclusions can be made, Table 2. Future studies to evaluate the significance of sTILs in different ethnicities may be informative to delineate possible mechanisms contributing to known disparities they experience. Citation Format: Jami Fukui, Alana Taniguchi, Madison Meister, Ian Pagano, Jeffrey Killeen. Racial/ethnic differences in tumor infiltrating lymphocytes [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-06-13.