Clinicopathological correlates of γδ t cell infiltration in triple‐negative breast cancer

Abstract

The prognostic impact of the different tumor‐infiltrating lymphocyte (TIL) subpopula-tions in solid cancers is still debated. Here, we investigated the clinicopathological correlates and prognostic impact of TILs, particularly of γδ T cells, in 162 patients with triple‐negative breast cancer (TNBC). A high γδ T cell density (>6.625 γδ T cells/mm2) 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, γδ T cell infiltration (cutoff = 6.625 γδ T cells/mm2) 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 γδ 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 γδ T cell infiltrate is correlated with immune infiltration and might represent a candidate prognostic tool in patients with TNBC.