Abstract PO-154: Clinical and prognostic significance of tumor infiltrating lymphocytes of triple negative breast cancer in Colombian women

Abstract

Abstract Background: Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype, represents 10%-20% of all breast cancers and occurs more frequently in young Non- Hispanic Black and Latina women. TNBC is highly immunogenic due to the relatively high levels of tumor infiltrating lymphocytes (TILs) which in turn has been associated with long term survival as well as a risk reduction of death and recurrence. Little is known about TILs and its prognostic value in TNBCs from Latinas such as Colombian women. The goal of this study was to evaluate the differences in the clinic-pathological variables according to TILs levels. Also, to evaluate if TILs are an independent prognostic factor in TNBC from Colombian patients. Methods: We included 130 TNBC patients diagnosed between 2008-2016 at the Colombian National Cancer Institute. Analysis of TILs was performed on a single full-face hematoxylin and eosin (H&E) stained pre-treatment sections. TILs score was estimated as a proportion of intratumoral TILs (iTILs) and stromal TILs (sTILs) on tumoral area and was classified using a cut-off of 10% for sTILs and 1% for iTILs. Additionally, immunohistochemistry for PD-L1 (n=92), CD4 (n=40) and CD8 (n=40) was evaluated on three different fields of vision. Chi-squared test and ANOVA were used to test differences in clinic-pathological variables and Kaplan Meier analysis and long-rank test was used to explore differences in survival according to TILs. Results: High sTILs (≥10%) was observed in 36.4% of the patients. We observed that patients in the high sTILs group were usually diagnosed at early stages and with smaller tumors (<2cm) compared to patients with low sTILs (48.9% vs 23.2%, p<0.01 and 27.3% vs. 5.3%, p<0.01). Regarding treatment, a lower number of patients with high sTILs received neoadjuvant chemotherapy (46.8% vs. 74.4%, p<0.01 and mastectomy (53.2% vs. 74.4%, p=0.02) but had clinical complete response (cCR) (30% vs. 6.2%, p=0.053) compared to patients with low sTILs. Similar results were found for cCR in the iTILs positive group compared to iTILs negative group (13.8% vs. 0%, p<0.01). Differences in overall survival was observed according to sTILs (p<0.01). Cox regression analysis in a model adjusted by AJCC stage found low sTILs (<10%) as a prognostic factor associated with higher risk of death (HR: 1.65, 95% CI 0.99 – 2.77, p=0.05). Stromal and intratumoral CD4 and CD8 were evaluated, and patients were categorized according to the median of expression. For low iCD4 we observed a higher percentage of patients with node involvement (88.9% vs. 52.6%, p=0.04) and for the low iCD8 group we observed larger tumors (>5cm) (47.4% vs. 31.2%, p=0.03). Finally, PD-L1 expression was positive in 21.7% of the patients and was associated with high level of sTILs (p=0.02). Conclusions: Our results suggests that higher levels of sTILs in the TNBC are associated with a better prognosis. Further work is needed to explore the level of CD4, CD8 and PD-L1 expression in our patients to assess its clinical impact. Citation Format: Carlos A. Huertas, Mayra A. Ramirez, Henry J. Gonzalez, Juan C. Mejía, Laura Fejerman, Jovanny Zabaleta, María C. Sanabria, Silvia J. Serrano. Clinical and prognostic significance of tumor infiltrating lymphocytes of triple negative breast cancer in Colombian women [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-154.