Intratumoral CD103-positive tumour-infiltrating lymphocytes are associated with favourable prognosis in patients with triple-negative breast cancer.

AIMS

Cluster of differentiation 103 (CD103), a marker of tissue resident memory T cells, is expressed on subsets of CD8 T lymphocytes. We investigated the prognostic significance of CD103 intra-epithelial tumour-infiltrating lymphocytes (iTILs) in invasive breast cancer (IBC).

METHODS AND RESULTS

Immunohistochemistry was performed for CD103, CD8 and TGF-β isoforms (1, 2 and 3) on tissue microarrays of 1187 IBC samples. CD103 and CD8 iTILs were present in 904 (76.2%) and 854 (74%) cases with an overall mean ± standard deviation of 38.2 ± 100.2/mm and 30.4 ± 89.7/mm , respectively. The numbers of CD103 and CD8 iTILs were positively correlated, and CD103 iTILs outnumbered CD8 iTILs in HER2-positive and triple-negative breast cancer (TNBC). CD103 and CD8 iTIL densities were significantly higher in tumours of histological grade 3, absence of lymphovascular invasion, high Ki-67 index, high stromal TIL density or TGF-β3 expression. High CD103 iTIL density was associated with better disease-free survival (DFS, P = 0.007), but no significant association was observed for overall survival (OS). Subgroup analysis by cancer molecular subtype showed that CD103 iTIL count was prognostic only for TNBC (OS, P = 0.035; DFS, P = 0.009). CD8 iTIL density was significant for DFS, but not for OS, in the entire cohort and TNBC. In multivariate analysis, CD103 iTIL density was an independent prognostic factor of OS (P = 0.02) and DFS (P = 0.007) in TNBC, while CD8 iTIL density was not significant for survival.

CONCLUSIONS

CD103 iTIL density can serve as a predictor of good prognosis in patients with TNBC.