Elevation of the Prognostic Factor Plasma Fibrinogen Reflects the Immunosuppressive Tumor Microenvironment in Esophageal Squamous Cell Carcinoma

Introduction: Despite previous reports on the clinical significance of plasma fibrinogen (FNG) levels as a prognostic indicator of ESCC, its underlying mechanism remains unclear. This study aimed to validate the prognostic impact of plasma FNG levels and clarify its relationship with primary tumors in patients with esophageal squamous cell carcinoma (ESCC). Methods: The prognostic impact of FNG was evaluated in patients with ESCC who underwent esophagectomy between 2000 and 2019. The RNA sequencing of the primary ESCC site, which was from pre-operative biopsy, was performed, followed by immune profile characterization using an immunogram. Those profiles were assessed via the immunohistochemical staining of tumor-associated macrophages (TAMs) and clinical response to nivolumab. Results: Multivariate analysis identified FNG as a significant prognostic factor in ESCC. The immunogram suggested an immunosuppressive tumor environment in the high-FNG group. Immunostaining with the TAM markers CD163 and CD204, revealed that the high-FNG group had significantly higher number of TAMs compared with the low-FNG group. The immunosuppressive characteristics were clinically validated in patients with metastatic ESCC; those who had elevated FNG levels showed poor response to nivolumab. Conclusion: This study successfully validated the prognostic impact of plasma FNG levels in an expanded cohort with ESCC. Accordingly, our findings showed that increased plasma FNG reflects an immunosuppressive tumor microenvironment that facilitates tumor progression and poor responses to nivolumab.