Integrated analysis of tertiary lymphoid structures in relation to tumor-infiltrating lymphocytes and patient survival in pancreatic ductal adenocarcinoma.

BACKGROUND: Tertiary lymphoid structure (TLS) reflects an intense immune response against cancer, which correlates with favorable patient survival. However, the association of TLS with tumor-infiltrating lymphocytes (TILs) and clinical outcomes has not been investigated comprehensively in pancreatic ductal adenocarcinoma (PDAC).

METHODS: We utilized an integrative molecular pathological epidemiology database on 162 cases with resected PDAC, and examined TLS in relation to levels of TILs, patient survival, and treatment response. In whole-section slides, we assessed the formation of TLS and conducted immunohistochemistry for tumor-infiltrating T cells (CD4, CD8, CD45RO, and FOXP3). As confounding factors, we assessed alterations of four main driver genes (KRAS, TP53, CDKN2A [p16], and SMAD4) using next-generation sequencing and immunohistochemistry, and tumor CD274 (PD-L1) expression assessed by immunohistochemistry.

RESULTS: TLSs were found in 112 patients with PDAC (69.1%). TLS was associated with high levels of CD4+ TILs (multivariable odds ratio [OR], 3.50; 95% confidence interval [CI] 1.65-7.80; P = 0.0002), CD8+ TILs (multivariable OR, 11.0; 95% CI 4.57-29.7, P < 0.0001) and CD45RO+ TILs (multivariable OR, 2.65; 95% CI 1.25-5.80, P = 0.01), but not with levels of FOXP3+ TILs. TLS was associated with longer pancreatic cancer-specific survival (multivariable hazard ratio, 0.37; 95% CI 0.25-0.56, P < 0.0001) and favorable outcomes of adjuvant S-1-treatment. TLS was not associated with driver gene alterations but tumor CD274 negative expression.

CONCLUSIONS: Our comprehensive data supports the surrogacy of TLS for vigorous anti-tumor immune response characterized by high levels of helper and cytotoxic T cells and their prognostic role.