Strong CD8+ lymphocyte infiltration in combination with expression of HLA class I is associated with better tumor control in breast cancer patients treated with neoadjuvant chemotherapy.

Purpose: Tumor-infiltrating lymphocytes (TILs) are associated with pathological complete response (pCR) and survival after neoadjuvant chemotherapy (NAC) in patients with early breast cancer. We investigated the prognostic and predictive role of TILs, macrophages, and HLA class 1 expression after NAC with or without the potentially immune modulating compound zoledronic acid (ZA).
Methods: Baseline tumor biopsies from 196 patients in the NEOZOTAC trial were analyzed for CD8 (cytotoxic T-cells), FoxP3 (regulatory T-cells), CD68 (macrophages), and HLA class I (HCA2/HC10) expression by immunohistochemistry and subsequently related to pCR and disease-free survival (DFS).
Results: A strong intratumoral CD8+ infiltration or expression of HLA class 1 by cancer cells was associated with a higher pCR rate (p < 0.05). Clinical benefit of high CD8+ T-cell infiltration was found when cancer cells expressed HLA class 1 (pCR: 21.8% vs. 6.7%, p = 0.04) but not when HLA class 1 expression was lost or downregulated (pCR: 5.9% vs. 0%, p = 0.38). Interaction analyses revealed survival benefit between HLA class 1 expression and strong CD8+ T-cell infiltration, whereas in the absence or downregulation of HLA class 1 expression, high levels of CD8+ T-cells were associated with survival disadvantage (p for interaction 0.01; hazard ratio 0.41, 95% CI 0.15-1.10, p = 0.08 and hazard ratio 7.67, 95% CI 0.88-66.4, p = 0.07, respectively). Baseline immune markers were not related to ZA treatment.
Conclusions: Strong baseline tumor infiltration with CD8+ T-cells in the presence of tumoral HLA class 1 expression in patients with HER2-negative breast cancer is related to a higher pCR rate and a better DFS after NAC.