Clinicopathological Correlates Of Gamma Delta T Cell Infiltration In Triple-Negative Breast Cancer

Simple SummaryThe prognostic impact of the different tumor-infiltrating lymphocyte (TIL) subpopulations remains debated in solid cancers. We investigated the clinicopathological correlates and prognostic impact of TILs, particularly of gamma delta T cells, in 162 triple-negative breast cancer (TNBC) patients. A high gamma delta T cell density was significantly associated with younger age, higher tumor histological grade, adjuvant chemotherapy, BRCA1 promoter methylation, TIL density, and PD-L1 and PD-1 expression. In multivariate analyses, gamma delta T cell infiltration was an independent prognostic factor. However, this prognostic impact varied according to the tumor PIK3CA mutational status. High gamma delta T cell infiltration was associated with better survival in patients with PIK3CA wild-type tumors, without significant difference in the PIK3CA-mutated tumor subgroup. Altogether, these data suggest that high gamma delta T cell infiltrate is correlated with immune infiltration and might represent a prognostic tool in TNBC patients.The prognostic impact of the different tumor-infiltrating lymphocyte (TIL) subpopulations in solid cancers is still debated. Here, we investigated the clinicopathological correlates and prognostic impact of TILs, particularly of gamma delta T cells, in 162 patients with triple-negative breast cancer (TNBC). A high gamma delta T cell density (>6.625 gamma delta T cells/mm(2)) was associated with younger age (p = 0.008), higher tumor histological grade (p = 0.002), adjuvant chemotherapy (p = 0.010), BRCA1 promoter methylation (p = 0.010), TIL density (p < 0.001), and PD-L1 (p < 0.001) and PD-1 expression (p = 0.040). In multivariate analyses, gamma delta T cell infiltration (cutoff = 6.625 gamma delta T cells/mm(2)) was an independent prognostic factor (5-year relapse-free survival: 63.3% vs. 89.8%, p = 0.027; 5-year overall survival: 73.8% vs. 89.9%, p = 0.031, for low vs. high infiltration). This prognostic impact varied according to the tumor PIK3CA mutational status. High gamma delta T cell infiltration was associated with better survival in patients with PIK3CA wild-type tumors, but the difference was not significant in the subgroup with PIK3CA-mutated tumors. Altogether, these data suggest that high gamma delta T cell infiltrate is correlated with immune infiltration and might represent a candidate prognostic tool in patients with TNBC.