[Evaluation of PD-L1 expression and intratumoral lymphocytic infiltration in triple-negative invasive breast carcinoma].

INTRODUCTION: Triple negative breast cancer endophenotype (TNBC) is one of the least frequent and without therapeutic target; therefore we propose to study the correlation of PD-L1 immune checkpoint with the establishment of tumor microenvironment assessed by intratumoral stromal lymphocyte infiltration (TILS) and its importance in clinical practice.

METHODS: A retrospective case-control study was performed, with 31 cases of triple-negative infiltrating breast carcinoma and 57 unmatched controls of Luminal A, Luminal B and HER-2 endophenotype seen in one year. The following variables were evaluated: histologic type and grade, PD-L1 expression with clone 22C3, TILS, lymphovascular invasion, tumor size, lymph node involvement and metastasis. Statistical analysis was performed with the chi-square test and Spearman correlation coefficient test.

RESULTS: a statistically significant negative correlation was found between TILS and PD-L1 (rho - 0.106, p 0.025), indicating that the higher the expression of PD-L1, the lower the intratumoral lymphocytic infiltration. In the TILS B (10-40% TILS) and C (40-90% TILS) groups where there was a marked intratumoral inflammatory infiltrate, a greater number of patients were negative for PD-L1 (CPS <10) with 16 and 10 cases, respectively. For TNBC cases a negative association coefficient was identified (rho -0.378) with statistical significance (p 0.01).

DISCUSSION: The association between TNBC, TILS and PDL1 expression was established, which is important for the establishment of target therapies and the development of precision medicine.