Relationship between the immune microenvironment of different locations in a primary tumour and clinical outcomes of oesophageal squamous cell carcinoma

BACKGROUND: Tumour microenvironments can differ according to intratumoural locations. We investigated the immune status at different locations in primary tumours and its clinical significance in oesophageal squamous cell carcinoma (ESCC). METHODS: The number of CD8(+) tumour-infiltrating immune cells (TIICs) and PD-1(+) TIICs, and PD-L1 expression on tumour cells (PD-L1TC) were immunohistochemically examined in the surface (Surf), centre (Cent) and invasive front (Inv) of tumours surgically resected from 192 patients with ESCC. RESULTS: The PD-L1(+) rate was lower in Inv than in Cent (12.0% vs. 18.2%, P = 0.012), although the numbers of CD8+ TIICs and PD1(+) TIICs were comparable among intratumoural locations. High numbers of CD8(+) and PD-1(+) TIICs and positive PD-L1TC were related to better overall survival (OS) only in Surf and Cent (CD8: P = 0.012 in Surf, 0.018 in Cent, and 0.165 in Inv; PD-1: P = 0.028 in Surf, 0.021 in Cent, and 0.208 in Inv; and PD-L1: 0.044 in Surf, 0.026 in Cent, and 0.718 in Inv). Positive PD-L1TC in Surf and/or Cent but not in Inv demonstrated a strong tendency toward better OS (P = 0.053). CONCLUSIONS: Immune microenvironments according to the intratumoural location have different effects on the survival of patients with ESCC.