Abstract PR007: Tumoral infiltrating lymphocytes as a prognostic factor in triple negative breast cancer patients from Colombia

Introduction: Triple negative breast cancer (TNBC), occurs in 10%-20% of all breast cancer and presents a higher frequency in Latinas compared to non-Hispanic white women. It is highly immunogenic and high levels of tumor infiltrating lymphocytes (TILs) have been associated with a better overall survival and higher probability to achieve pathological complete response (pCR). Objective: This is the first study in Colombian women aimed to explore stromal TILs (sTILs) level and composition as a prognostic and predictive biomarker in TNBC. Methods: A total of 195 TNBC tumor biospecimens from patients diagnosed between 2008-2016 in 3 Colombian health institutions were included. Stromal TILs (sTILs) was evaluated following the recommendations of the International TILs Working Group 2014 in hematoxylin & eosin slides from pre-treatment samples. The number of positive cells for CD4 and CD8 was evaluated by immunohistochemistry and digital image capture. Parametric and non-parametric tests were used to evaluate differences in clinic-pathological characteristics according to sTILs levels and composition. Differences in overall survival were analyzed using Kaplan-Meier curves and the log-rank test. Cox regression analysis was used to analyze sTILs as a prognostic marker for overall survival. A logistic regression model was applied to evaluate the association of sTILs with pCR. Results: Tumors with high sTILs levels were more likely to be early stage (64.4% stage I/II) compared to tumors with low sTILs levels (35.5%). Additionally, when compared patients with high sTILs vs. low sTILs, a higher percentage of patients with high sTILs didn’t receive neoadjuvant chemotherapy (NAC) (high:50% vs. low:32.7%, p=0.025) and received more conservative surgeries (high:60% vs. low:37.9%, p