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.