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Stromal tumor-infiltrating lymphocyte (sTIL) enrichment in pretreatment breast tumors has been associated with superior response to neoadjuvant treatment and survival. In a population-based cohort, we studied sTIL-survival associations by race and ethnicity. We assessed associations of continuous sTIL scores and sTIL-enriched breast cancers (defined as percent lymphocytic infiltration of tumor stroma or cell nests at cutoffs of 30%, 50%, and 70%) with clinical and epidemiologic characteristics and conducted multivariable survival analyses. Although we identified no difference in sTIL score by race and ethnicity, higher continuous sTIL score was associated with lower breast cancer-specific mortality only among non-Hispanic White and Asian American but not African American and Hispanic women. This finding suggests that complex factors influence treatment response and survival, given that sTIL enrichment was not associated with a survival advantage among women from minoritized groups, who more often experience health disparities. Further study of patient selection for sTIL-guided treatment strategies is warranted., (© The Author(s) 2024. Published by Oxford University Press.)

Purpose: Tumor-infiltrating lymphocytes (TIL) in pretreatment biopsies are associated with improved survival in triple-negative breast cancer (TNBC). We investigated whether higher peripheral lymphocyte counts are associated with lower breast cancer-specific mortality (BCM) and overall mortality (OM) in TNBC. Experimental Design: Data on treatments and diagnostic tests from electronic medical records of two health care systems were linked with demographic, clinical, pathologic, and mortality data from the California Cancer Registry. Multivariable regression models adjusted for age, race/ethnicity, socioeconomic status, cancer stage, grade, neoadjuvant/adjuvant chemotherapy use, radiotherapy use, and germline BRCA1/2 mutations were used to evaluate associations between absolute lymphocyte count (ALC), BCM, and OM. For a subgroup with TIL data available, we explored the relationship between TILs and peripheral lymphocyte counts. Results: A total of 1,463 stage I-III TNBC patients were diagnosed from 2000 to 2014; 1,113 (76%) received neoadjuvant/adjuvant chemotherapy within 1 year of diagnosis. Of 759 patients with available ALC data, 481 (63.4%) were ever lymphopenic (minimum ALC <1.0 K/μL). On multivariable analysis, higher minimum ALC, but not absolute neutrophil count, predicted lower OM [HR = 0.23; 95% confidence interval (CI), 0.16-0.35] and BCM (HR = 0.19; CI, 0.11-0.34). Five-year probability of BCM was 15% for patients who were ever lymphopenic versus 4% for those who were not. An exploratory analysis ( n = 70) showed a significant association between TILs and higher peripheral lymphocyte counts during neoadjuvant chemotherapy. Conclusions: Higher peripheral lymphocyte counts predicted lower mortality from early-stage, potentially curable TNBC, suggesting that immune function may enhance the effectiveness of early TNBC treatment. Clin Cancer Res; 24(12); 2851-8. ©2018 AACR ., (©2018 American Association for Cancer Research.)

The distribution of breast cancer molecular subtypes has been shown to vary by race/ethnicity, highlighting the importance of host factors in breast tumor biology. We undertook the current analysis to determine population-based distributions of breast cancer subtypes among six ethnic Asian groups in California. We defined immunohistochemical (IHC) surrogates for each breast cancer subtype among Chinese, Japanese, Filipina, Korean, Vietnamese, and South Asian patients diagnosed with incident, primary, invasive breast cancer between 2002 and 2007 in the California Cancer Registry as: hormone receptor-positive (HR+)/HER2- [estrogen receptor-positive (ER+) and/or progesterone receptor-positive (PR+), human epidermal growth factor receptor 2-negative (HER2-)], triple-negative (ER-, PR-, and HER2-), and HER2-positive (ER±, PR±, and HER2+). We calculated frequencies of breast cancer subtypes among Asian ethnic groups and evaluated their associations with clinical and demographic factors. Complete IHC data were available for 8,140 Asian women. Compared to non-Hispanic White women, Korean [odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.5-2.2], Filipina (OR = 1.3, 95% CI = 1.2-1.5), Vietnamese (OR = 1.3, 95% CI = 1.1-1.6), and Chinese (OR = 1.1, 95% CI = 1.0-1.3) women had a significantly increased risk of being diagnosed with HER2-positive breast cancer subtypes after adjusting for age, stage, grade, socioeconomic status, histology, diagnosis year, nativity, and hospital ownership status. We report a significant ethnic disparity in HER2-positive breast cancer in a large population-based cohort enriched for Asian-Americans. Given the poor prognosis and high treatment costs of HER2-positive breast cancer, our results have implications for healthcare resource utilization, cancer biology, and clinical care.