Abstract 3437: Stromal tumor-infiltrating lymphocytes in association with body size and composition among Black and White women with breast cancer

Abstract Background: Obesity is a major risk factor for breast cancer and negatively affects disease prognosis. Tumor-infiltrating lymphocytes (TILs) in the stroma of breast tissue play a major role in eliminating cancer cells and modulating immunotherapy efficacy. We aim to study the association between body size and composition with stromal TILs in breast tumor tissue by race. Methods: The study included 920 Black and 395 White women with newly diagnosed invasive breast cancer who have stromal TIL scores from the Women’s Circle of Health Study (WCHS). Body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) were measured during the home interview. Pre-treatment H&E-stained tumor tissue sections were reviewed by our study pathologist and stromal TILs were scored on a scale of 0-100% at 10% increment according to the recommendations of the International TILs Working Group. Linear regressions adjusting for age at diagnosis, tumor grade, stage, and molecular subtype were used to test the differences in TILs across the categories of body size and composition indicators separately for Black and White women. Results: A higher stromal TILs score was associated with more aggressive breast cancer features, including higher grade, larger tumor size, more advanced stage, hormone receptor (HR) negativity, and human epidermal growth factor receptor 2 (HER2) positivity in both Black and White women (all P<0.05). Among Black women, WHR >0.90 vs ≤0.85 was associated with lower TILs overall (β = -3.5%, P = 0.045) and in triple-negative tumors (β = -12.3%, P = 0.003). Among White women, BMI 25.0 - 29.9 vs <25 was associated with higher TILs in HR-/HER2+ tumors (β = 28.1%, P = 0.031). A pattern suggested that BMI ≥30 vs <25 was associated with lower TILs in both HR-/HER2+ (β = -10.2, P=0.52) and triple-negative (β = -12.8, P=0.14) tumors, although the associations were not significant. No association was observed between TILs and any of the body composition parameters in women with HR+ tumors. Conclusions and Relevance: Body size and composition correlate with stromal TILs mainly in patients with HR- tumors, and this relation may be race-dependent. These findings suggest that body size and composition potentially modulate breast cancer treatment outcomes at least in part through TILs-dependent mechanisms. Funding: This work was in part supported by grants from the US National Institutes of Health (P01CA151135, R01CA100598, R01CA185623, P30CA016056, P30CA072720, K07CA201334, and R37CA248371), US Army Medical Research and Material Command (DAMD-17-01-1-0334), the Breast Cancer Research Foundation (CBA), and the Philip L. Hubbell family. Citation Format: Rand T. Akasheh, Thaer Khoury, Song Yao, Angela Omilian, Chi-Chen Hong, Elisa V. Bandera, Bonnie Qin, Nur Zeinomar, Christine Ambrosone, Ting-Yuan David Cheng. Stromal tumor-infiltrating lymphocytes in association with body size and composition among Black and White women with breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3437.